The Nature of Alcohol

Yeasts and Alcoholic Fermentation

The Qualities of Alcohol

Alcohol as a Drug: Intoxication

How the Body Metabolizes Alcohol

Cooking with Alcohol

Alcoholic Liquids and Wood Barrels

Wine

The History of Wine

Wine Grapes

Making Wine

Special Wines

Storing and Serving Wine

Enjoying Wine

Beer

The Evolution of Beer

Brewing Ingredients: Malt

Brewing Ingredients: Hops

Brewing Beer

Storing and Serving Beer

Kinds and Qualities of Beer

Asian Rice Alcohols: Chinese Chiu and Japanese Sake

Sweet Moldy Grains

Starch-Digesting Molds

Brewing Rice Alcohols

Distilled Spirits

The History of Distilled Spirits

Making Distilled Alcohols

Serving and Enjoying Spirits

Kinds of Spirits

Vinegar

An Ancient Ingredient

The Virtues of Acetic Acid

The Acetic Fermentation

Vinegar Production

Common Kinds of Vinegar

Balsamic Vinegar

Sherry Vinegar

Like all good foods, wine, beer, and spirits nourish and satisfy the body. What sets them apart is the very direct way in which they touch the mind. They contain alcohol, which is both a source of energy and a drug. In moderate amounts, alcohol causes us to feel and express emotions of all kinds — happiness, conviviality, sadness, anger — with more freedom. In large amounts, it’s a narcotic: it numbs feeling and clouds thought. Alcoholic drinks thus offer various degrees of release from our usual state of mind. Small wonder that they were once considered an earthly version of the nectar of the gods, foods that give mortals a taste of being carefree masters of life!

Humankind has always had a thirst for alcohol, and now satisfies it with mass-produced drinks that offer an inexpensive respite from the world and its cares. But some wines and beers and spirits are among the most finely crafted foods there are, the best that the world and care have to offer. Their flavor can be so rich, balanced, dynamic, and persistent that they touch the mind not with release from the world, but with a heightened attentiveness and connection to it.

Wine, beer, and spirits are the creation of microscopic yeasts, which break food sugars down into alcohol molecules. Alcohol is a volatile substance whose own aroma is relatively diffuse. It has the effect of lending a new dimension to the flavor of grapes and grains, a kind of open stage on which the food’s own volatile molecules can appear. Yeasts are also prodigious flavor chemists, so during the fermentation they fill that stage with dozens of new aromas. The winemaker or brewer then directs the transformation of this teeming, unruly cast into a balanced, harmonious ensemble.

Though they share this basic nature, wine and beer and spirits are very different foods. Wine begins with fruits that are fragrant and sweet with sugars, and therefore ready-made to ferment into an aromatic drink — but only during the few days of the year when they’re ripe. Grapes and wine are a gift of nature, a form of grace, which the winemaker must accept when they’re given, and can leave largely to themselves to realize their innate potential for producing flavor. Beer and rice alcohols, by contrast, are the expression of everyday human effort and ingenuity. They’re made from sugarless, aroma-less dry grains, the charmless but dependable staff of life. Brewers transform grains into something fermentable and aromatic by sprouting them or cultivating molds on them for days, and cooking them for hours. They can do this at any time of the year, anywhere in the world. Beer is thus our universal alcohol, comfortably local and everyday and ordinary, yet sometimes extraordinary. And distilled spirits are the heart of wine and beer, concentrates of their volatile and aromatic content, and drinks of unmatched intensity.

The pleasure of tasting a good beer or wine or spirit grows with the recognition that its flavor is the expression of many natural, cultural, and personal particulars: a place and its traditions, certain plants and the soil they grew in, a year and its weather, the course of fermentation and maturation, the taste and skills of the maker. Their rich natural and human parentage explains why alcohols are so absorbingly diverse, and why a thoughtful sip can momentarily fill us with the world and delight.

The Nature of Alcohol

Alcohol molecules are made in many living cells as a by-product of breaking down sugar molecules for their chemical energy. Most cells then break down the alcohol molecules to extract their energy content too. The great exception to this rule is certain yeasts, which excrete alcohol into their surroundings. Like the lactic acid in cheeses and pickled vegetables, like the powerful aromas in herbs and spices, the alcohol in wine and beer is a defensive chemical weapon, which the yeasts deploy to protect themselves against competition from other microbes. Alcohol is toxic to living cells. Even the yeasts that make it for us can only tolerate a certain amount. The pleasant feeling that it gives us is a manifestation of the fact that it’s disrupting the normal function of our brain cells.

Yeast. Cells of brewer’s yeast, Saccharomyces cerevisiae, as seen through an electron microscope. Each is about 0.005 mm in diameter. The cell at the upper right center is in the process of reproducing, and bears the scars of previous buddings.

Yeasts and Alcoholic Fermentation

Yeasts are a group of about 160 species of single-celled microscopic molds. Not all are useful: some cause the spoilage of fruits and vegetables, some cause human disease (for example, the yeast infection of Candida albicans). Most of the yeasts used in making bread and alcoholic drinks are members of the genus Saccharomyces, whose name means “sugar fungus.” We cultivate them for the same reason that we use particular bacteria to sour milk: they make foods resistant to infection by other microbes, and produce substances that are mainly pleasant to us. Essential to the yeasts’ production of alcohol is their ability to survive on very little oxygen, which most living cells use to burn fuel molecules for energy, leaving behind only carbon dioxide and water. In the absence of oxygen, the fuel can be broken down only partly. The overall equation for the production of energy from glucose without oxygen goes like this:

C₆H₁₂O₆ 2CH₃CH₂OH + 2CO₂ + energy

Glucose alcohol + carbon dioxide + energy

Yeasts introduce a variety of other compounds into the grape juice or grain mash that contributes characteristic flavors. For example, they produce savory succinic acid, and transform amino acids in the liquid into “higher,” or longer-chain alcohols; they combine alcohols with acids to make fruity-smelling esters; they produce sulfur compounds reminiscent of cooked vegetables, coffee, and toast. And when a yeast cell dies, its enzymatic machinery digests the cell and releases its contents into the liquid, where they continue to generate flavor. Because growing yeast cells synthesize proteins and B vitamins, they can actually make a fruit juice or cereal mash more nutritious than it was when fresh.

The Qualities of Alcohol

In chemistry, the term alcohol is applied to a large family of substances with a similar molecular structure. Our everyday word alcohol refers to one particular member of this family, which chemists call ethyl alcohol, or ethanol. In this chapter I’ll use alcohol in its common sense, but I’ll also refer to “higher” alcohols, or molecules in the alcohol family with more atoms than ethanol has.

Ethanol, or common alcohol. The versatile ethanol molecule has one end that resembles the fatty-acid carbon chain of fats and oils, and one end that resembles water.

Physical and Chemical Qualities Pure alcohol is a clear, colorless liquid. The alcohol molecule is a small one, CH₃CH₂OH, whose backbone is just two carbon atoms. One end of the alcohol molecule, the CH₃, resembles fats and oils, while the OH group at the other end is two-thirds of a water molecule. Alcohol is therefore a versatile liquid. It mixes easily with water, but also with fatty substances, including cell membranes, which it excels at penetrating, and aroma molecules and carotenoid pigments, which it excels at extracting from cells. The higher alcohols, which yeasts also produce in small quantities and which become concentrated in distilled spirits, have a longer fat-like end to their molecules (p. 762), and behave more like fats. They lend an oily, viscous quality to whiskies and other spirits. They also tend to concentrate in the membranes of our cells, and therefore are more irritating and more potent narcotics than simple alcohol.

Several of alcohol’s physical properties have important consequences for the cook and food lover.

• Alcohol is more volatile than water, more easily evaporated and brought to the boil. Its low boiling point, 176ºF/78ºC, is what makes it possible to distill alcohol into a much stronger solution than wine or beer.
• Alcohol is flammable, which makes possible spectacular flaming dishes fueled by brandy or rum. The food doesn’t get scorched because the heat of combustion is fully absorbed by the vaporization of the spirits’ water.
• Alcohol has a much lower freezing point than water, –173ºF/–114ºC. This makes it possible to concentrate alcoholic liquids in winter cold or the freezer (see box, p. 761).
• A given volume of alcohol weighs 80% as much as the same volume of water, so a mixture of alcohol and water is lighter than pure water. This helps makes possible layered cocktails (see box, p. 770).

Alcohol and Flavor We experience the presence of alcohol in a food through our senses of taste, smell, and touch. The alcohol molecule bears some resemblance to a sugar molecule, and indeed it has a slightly sweet taste. At high concentrations, those typical of distilled spirits and even some strong wines, alcohol is irritating, and produces a pungent, “hot” sensation in the mouth, as well as in the nose. As a volatile chemical, alcohol has its own distinctive aroma, which we experience at its purest in unflavored grain alcohol or vodka. Its chemical compatibility with other aroma compounds means that concentrated alcohol tends to bind aromas in foods and drinks and inhibit their release into the air. But at very low concentrations, around 1% or less, alcohol actually enhances the release of fruity esters and other aroma molecules into the air. This is one reason that wine, vodka, and other alcohols are valuable ingredients in general cooking, provided that the proportion is small or the alcohol mostly removed by long cooking.

Effects on Living Things One consequence of alcohol’s chemical versatility is that it readily penetrates the membranes of living cells, which are made in part of fat-like molecules. When it does so, it disturbs the action of the membrane proteins. A high enough concentration of alcohol will cause such a disturbance that this critical boundary between cell and environment fails, and the cell dies. The yeasts that produce alcohol can tolerate a concentration of about 20%, and most other microbes are killed by much less. When the solution also contains acid or sugar, as in wines, alcohol is an even more effective microbial poison. This is why, unlike beer and wine, distilled spirits and such alcohol-fortified wines as sherry and port don’t spoil after they’re opened.

Our own pleasant inebriation when we drink alcohol is in part a symptom of mild membrane and protein disturbance throughout our nervous system.

Alcohol as a Drug: Intoxication

Alcohol is a drug: it alters the operation of the various tissues into which it diffuses. We value it most for its influence on the central nervous system, where it acts as a narcotic. The fact that it seems to stimulate more animated, excited behavior than usual is actually a symptom of its depressant effect on the higher functions of the brain, those that normally control our behavior with various kinds of inhibition. As more alcohol reaches the brain, it interferes with more basic processes: memory, concentration, and thinking in general; muscular coordination, speech, vision. With regard to the idea that alcohol is an aphrodisiac, modern investigators continue to cite the authority of the Porter in Shakespeare’s Macbeth, who says of drink that “Lechery, sir, it provokes, and unprovokes: it provokes the desire, but it takes away the performance.”

The degree to which someone is intoxicated depends on the concentration of alcohol in the cells. Once alcohol is absorbed from the digestive tract, the blood rapidly distributes it to all body fluids, and it readily diffuses into and across membranes to penetrate all cells. Large people can therefore drink more than small people without being drunker: they have a greater volume of body fluids and cells in which to dilute the alcohol. Impaired coordination and impulsive behavior usually appear when the concentration of alcohol in the blood is 0.02–0.03%. Falling-over drunkenness is the result at 0.15%, and 0.4% can be fatal.

As drugs go, alcohol is a relatively weak one. It takes grams of pure alcohol, not milligrams, to have noticeable effects, and this allows us to enjoy moderate amounts of wine and beer without harming ourselves. But like other narcotic drugs, alcohol can be addictive, and the habitual consumption of large quantities is destructive. It has been the cause of widespread misery and premature death for thousands of years, and it still is. Alcohol and the molecule to which it’s first metabolized, acetalde-hyde, disrupt many systems and organs in the body. Their constant presence can therefore cause a broad range of serious and even fatal diseases.

How the Body Metabolizes Alcohol

Our bodies eliminate alcohol by breaking it down in a series of chemical reactions and using the energy freed by those reactions. Alcohol’s chemical structure has similarities to both sugar and fat, and it has a nutritional value between the two, around 7 calories per gram (sugar has 4 calories per gram, fat 9). It provides around 5% of the calories in the American diet, much more among heavy drinkers.

Alcohol is broken down and converted into energy in two organs, the stomach and the liver. The “first-pass” metabolism of alcohol in the stomach consumes a portion before it gets to the small intestine and then into the blood. That portion is around 30% in men, but only 10% in women. Men therefore experience a slower rise in blood alcohol when they drink, and can drink more before they feel its effects. And there are strong genetic influences on how well individuals are able to handle alcohol.

Overall, the body can metabolize around 10–15 grams of alcohol per hour, the equivalent of one standard-sized drink every 60–90 minutes. The level of alcohol in the blood reaches a maximum 30–60 minutes after consumption. Foods, and especially fats and oils, delay the passage of the stomach’s contents into the small intestine, giving the stomach enzymes more time to work, slowing the rise in blood alcohol, and reducing its peak to about half of what it reaches on an empty stomach. On the other hand, aspirin interferes with the stomach’s alcohol metabolism and so causes a quicker rise in blood alcohol levels. The carbon dioxide bubbles in sparkling wines and beer cause the same accelerated rise by as yet unknown means.

The Hangover Then there’s the misery of the hangover, the general feeling of illness that we wake up with the morning after we’ve had too much alcohol. The folk remedies for this affliction are many and ancient. In medieval times, the medical school of Salerno was already recommending the hair of the dog:

Si nocturna tibi noceat potatio vini,

Hoc tu mane bibas iterum, et fuerit medicina.

If an evening of wine does you in,

More the next morning will be medicine.

The hangover is in part a mild withdrawal syndrome. The night before, the body adjusted to a high concentration of alcohol and related narcotic chemicals, but by morning the drug is going or gone. Hyper-sensitivity to sound and light, for example, may be a leftover compensation for the general depression of the nervous system. The logic of the morning-after drink is simple but insidious: it restores many of the conditions to which the body had become accustomed, as well as lightly anesthetizing it. But this only postpones the body’s true recovery from intoxication.

Only a few of the different symptoms that constitute a hangover can be directly treated. The dry mouth and headache can be due to the dehydration that alcohol causes, so that drinking liquids may relieve them. Alcohol can also cause a headache by enlarging the cranial blood vessels; the caffeine in coffee and tea has the opposite effect, and may bring some relief.

Cooking with Alcohol

Cooks use wines, beers, and distilled spirits as ingredients in a broad range of dishes, from savory soups and sauces and stews to sweet creams and cakes, soufflés and sorbets. They contribute distinctive flavors, often including acidity, sweetness, and savoriness (from glutamic and succinic acids), and the aromatic dimension provided by alcohol and other volatile substances. Some qualities can be a challenge for the cook to work with, including the astringency of red wines (p. 737) and the bitterness of most beers. The alcohol itself also provides a third kind of liquid — in addition to water and oil — into which flavor and color molecules can be extracted and dissolved, as well as reactive molecules that can combine with other substances in the food to generate new aromas and greater depth of flavor. While large amounts of alcohol tend to trap other volatile molecules in the food, small traces boost their volatility and so intensify aroma.

At the same time that alcohol itself can be an asset for the cook, it can also be a liability. Alcohol has its own pungent, slightly medicinal qualities, and these qualities are heightened and can become harsh in hot foods. Cooks may therefore simmer or boil sauces for some time to evaporate off as much alcohol as possible. In the showy preparation called the flambé, from the French for “to flame,” they ignite the heated vapors of spirits and high-alcohol wines into flickering, ghostly blue flames to burn off the alcohol and give a lightly singed flavor to a dish. However, none of these techniques leave a food free of alcohol. Experiments have shown that long-simmered stews retain about 5% of the alcohol initially added, briefly cooked dishes from 10 to 50%, and flambés as much as 75%.

Alcoholic Liquids and Wood Barrels

The great good fortune of wine and beer is that microbes can “spoil” fruit juice and gruel into something both delicious and pleasantly inebriating. A few centuries ago, winemakers and distillers discovered another remarkable piece of good luck: simply storing wine, spirits, and vinegars in wood barrels turns out to give them a new and complementary dimension of flavor.

Oak and Its Qualities Though chestnut and cedar have been used in Europe and redwood in the United States, most barrels for aging wines and spirits are made from oak. Oak heartwood, the older inner wood, is a mass of dead cells that supports the outer living layers. The heartwood cells are filled with compounds that deter boring insects. These are mainly tannins, but they include such aromatic compounds as clove-like eugenol, vanilla-like vanillin, and oaky “oak lactones,” relatives of the characteristic aromatics of coconut and peach. From 90 to 95% of the heartwood solids are cell-wall molecules, cellulose, hemicellulose, and lignin. These are mostly insoluble, but the lignins can be partly broken down and extracted by strong alcohol, and all can be transformed into new aromatic molecules when the wood is heated during barrel making (p. 449).

Coopers rely mainly on two European oak species (Quercus robur and Q. sessilis), and ten North American species, the most important being the white oak (Q. alba). The European species are mostly made into wine barrels, American oak into barrels for aging distilled spirits. American oak tends to have lower levels of extractable tannins and higher levels of the oak lactones and vanillin.

Making Barrels: Forming and Cooking In order to make barrels, the cooper splits the heartwood into pieces, dries them, and forms them into thin, elongated staves, which are then roughly hooped together and heated to make them more pliable and easily bent into the final barrel shape. In Europe, the barrel interior is heated with a small brazier of burning wood scraps to 400ºF/200ºC. Once the softened staves have been tightly hooped into their final positions, the interior is “toasted” further at 300–400ºF/150–200ºC, for 5 to 20 minutes, depending on the degree of cooking desired: less for wine barrels, more for spirits. In the United States, the heat treatment for whiskey barrels is more extreme. The hooped staves are first steamed to soften them, and then the barrel interior is charred with an open gas burner for from 15 to 45 seconds.

Barrel Flavors Several things happen when alcoholic liquids are stored in new barrels. First, the liquid extracts soluble materials that contribute color and flavor, including tannins, oak and clove and vanilla aromas, and the sugars, browning-reaction products, and smoky volatiles formed when the barrel was heated. In the charred American barrels used for whiskey, the carbonized surface acts something like an activated charcoal absorbant, removing some materials from the whiskey and so accelerating the maturation of its flavor. Gaps and pores in the wood allow the liquid to absorb limited amounts of oxygen. And the rich chemical brew of wine or spirits, wood components, and oxygen slowly undergoes innumerable reactions and evolves toward a harmonious equilibrium.

New oak barrels give a pronounced flavor to liquids stored in them, one that can overwhelm the inherent qualities of delicate wines. The producer can control the contribution of the wood by limiting the aging time in new barrels, or by working with used barrels, which have already had much of their flavor components extracted.

Alternatives to Barrels Oak barrels are expensive, so only relatively expensive wines and spirits are aged in them. There are other ways of getting oak flavor into less expensive products. Boisés, extracts made by boiling wood chips in water, are a traditional finishing additive in French brandies, including Cognac and Armagnac. In recent years, large-volume winemakers have begun putting barrel staves, oak chips, and even sawdust into wines while they mature in containers made of steel and other inert materials.

Wine

The juice of the grape is just one of the naturally sweet liquids with which our ancestors learned to make alcoholic drinks. Perhaps just as ancient as grape wine is koumiss, the fermented mare’s milk of the central Asian nomads. One Greek word for wine, methu, came from the Indo-European word for fermented honey water, whose name in English is mead. The Romans fermented dates and figs. And before they tasted wine, the inhabitants of northern Europe drank apple juice fermented into cider.

But the grape turned out to be uniquely suited to the development of a diverse family of alcoholic drinks. The grapevine is a highly productive plant that can adapt to a wide range of soils and climates. Its fruits retain large amounts of an unusual acid, tartaric acid, which few microbes can metabolize, and which favors the growth of yeasts. The grapes ripen with enough sugar that the yeasts’ alcohol production can suppress the growth of nearly all other microbes. And they offer striking colors and a variety of flavors.

Thanks largely to these qualities, grapes are the world’s largest fruit crop, with about 70% of the annual production used to make wine. France, Italy, and Spain are the world’s largest wine producers and exporters.

The History of Wine

The evolution of wine is long and fascinating, and ongoing. Here are a few highlights.

Ancient Times: Aged Wines and Connoisseurship As I write, the earliest evidence we have for wine made from grapes, residues at the bottom of a pot found in western Iran, dates from around 6000 BCE. From 3000 BCE on, wine was a prominent part of trade in western Asia and Egypt. Wild grapes and the first wines were red, but the Egyptians had a color mutant of the grape plant and made white wines from it. They would ferment grape juice in large clay jars. The contents of the jars were eventually sampled and graded, and the jars marked, stoppered, and sealed with mud. The airtight containers allowed wine to be aged for years. Many wine amphoras found in the tombs of the pharaohs carry labels with the date of production, the region in which the wine was made, sometimes a brief description and the name of the winemaker. Wine connoisseurship is ancient!

Greece and Rome Phoenician and Greek traders introduced the cultivated vine throughout the Mediterranean basin, where the Greeks developed the cult of Dionysos, god of vegetation, the vine, and the temporary release from ordinary life that wine made possible. By Homer’s time, about 700 BCE, wine had become a standard beverage in Greece, one that was made strong, watered down before drinking, and graded in quality for freeman and slave. The culture of the vine was not established in Italy until about 200 BCE, but it took hold so well that the Greeks took to calling southern Italy Oenotria, “land of the grape.”

Over the next couple of centuries, Rome advanced the art of winemaking considerably. Pliny devoted a full book of his Natural History to the grape. He noted that there were now an infinite number of varieties, that the same grape could produce very different wines in different places, and named Italy, Greece, Egypt, and Gaul (France) as admired sources. Like the Egyptians, the Romans had airtight amphoras that allowed them to age wine for years without spoiling. The Greeks and Romans also preserved and flavored wines with tree resins or the pitch refined from them, salt, and spices.

It was in Roman times that wooden casks — an innovation of northern Europe — arrived along the Mediterranean as an alternative to clay amphoras. During subsequent centuries, they became the standard wine vessel, and amphoras disappeared. Casks had the advantage of being lighter and less fragile, but the disadvantage of not being airtight. This meant that wines could only be stored in them for a handful of years before they became overoxidized and unpleasant to drink. Excellent aged wines therefore disappeared along with the amphora, and only reappeared after more than a thousand years with the invention of the cork-stoppered bottle (p. 724).

The Spread of Winemaking in Europe; the Rise of France After the fall of Rome around the 5th century CE, Christian monasteries advanced the arts of viticulture and winemaking in Europe. Local rulers endowed them with tracts of land, which they then cleared of forest and reclaimed from swamps, bringing systematic, organized agriculture to sparsely settled regions, and the grape to northern France and Germany. Wine was required for the sacrament of Communion, and it and beer were made for daily consumption, to serve guests, and to sell. It was in the Middle Ages that the wines of Burgundy became famous.

From the late Middle Ages on, France slowly became the preeminent source of wine in Europe. By the 1600s the wines of France, and especially Bordeaux, which had the advantage being a port, were important exports to England and Holland. Meanwhile Italy fell behind, a victim of political and economic circumstance. Until the middle of the 19th century it was not a nation but a collection of city-states, each with protective tariffs and little of the international trade that brought competition and improvement to the wine regions of France. Most of the wine was consumed locally, and the grapevines grown not in vineyards but in sharecroppers’ plots, between rows of food plants or trained on trees.

New Wines and New Containers Early modern times brought the invention of several wonderful variants on plain fermented grape juice, and important improvements in wine storage. Sometime before 1600, Spanish winemakers found that they could both stabilize and give a new character to wines by fortifying them with brandy; the result was sherry. Around 1650, Hungarian winemakers managed to make deliciously concentrated and very sweet Tokaji wine from grapes infected by an otherwise destructive fungus, which came to be known as the “noble rot.” This was the forerunner of French Sauternes and similar sweet German wines. At about the same time, English importers of white wine from the Champagne region east of Paris discovered that they could make the wine delightfully bubbly by transferring it from barrel to bottles before it had finished fermenting. And a few decades later, the English developed port in the effort to stabilize strong red wines during their sea journey from Portugal. The shippers added distilled alcohol to the wines to prevent spoilage, and thus discovered the pleasures of fortified sweet red wines.

Bottles and Corks The 17th and 18th centuries brought two major innovations that once again made it possible to age wines for many years, a possibility that had disappeared when the impermeable amphora was replaced by wood barrels. These momentous developments were slim bottles and cork stoppers! The English discovery of sparkling Champagne depended on the fact that they had begun plugging bottle necks with compressible gas-tight cork instead of cloth, and that they had especially strong bottles that could withstand the inner pressure (the glass strength came from manufacturing with hot coal fires rather than wood fires). And during the 18th century, the wine bottle gradually evolved from a short, stout flask to the familiar elongated bottle. The bulky bottles were only used to convey the wine from barrel to table or to hold it for a day or two. When bottles had slimmed down enough that they could lie on their sides, their contents wetting the cork and preventing it from shrinking and admitting air, then wine could be stored in them for many years without spoiling, and sometimes with great improvements in flavor.

Pasteur and the Beginnings of a Scientific Understanding of Wine In 1863 the French Emperor Louis Napoleon asked the great chemist Louis Pasteur to study the “maladies” of wine. Three years later, Pasteur published the landmark Etudes sur le vin. Pasteur and others had already demonstrated that yeast is a living mass of microbes, and thus had made it possible to begin to identify and control the kinds of microbes that both make wine and spoil it. But Pasteur was the first to analyze the development of wine, to discover the central role of oxygen, and show why both barrel and bottle were indispensable for making good wine, the barrel for providing oxygen to the young wine to help mature it, and the bottle for excluding oxygen from the mature wine to help preserve it.

Scientific Approaches to Making Wine Pasteur planted the seed of a scientific approach to winemaking. That seed soon took root in both France and the United States. In the 1880s, the University of Bordeaux and the University of California established institutes of oenology. The Bordeaux group focused on understanding and improving traditional French methods for producing fine wines, and discovered the nature of the malolactic fermentation (p. 730). The California institute moved from Berkeley to Davis in 1928, and studied how best to build a wine industry in the absence of a local tradition, including determining what grape varieties were best suited to various climatic conditions. Today, thanks to this and similar work in a number of countries, and to the general modernization of winemaking, more good wine is being made in more parts of the world than ever before.

Traditional and Industrial Wines There’s now a spectrum of approaches among winemakers, and so a spectrum of wines from which we can choose. At one end is the relatively straightforward approach found in traditional winemaking regions: the grapes are grown in a place and with methods that maximize wine quality; they’re simply crushed, fermented, the new wine matured for some time, and bottled. At the other end of the spectrum are advanced manufacturing processes that treat grapes and wine like other industrial materials. These aim to approximate the qualities of the traditionally produced wine by nontraditional means that are less labor intensive and less expensive. The grapes themselves need not be coaxed to an ideal ripeness because the winemaker can use various separation technologies to adjust their content of water, sugar, acid, alcohol, and other components. The effects of barrel and bottle aging can be simulated inexpensively and rapidly by means of oak chips or sawdust, and the bubbling of pure oxygen through wine stored in huge steel tanks.

Industrial wines are marvels of reverse engineering, and often taste good, clean, and without obvious faults. Wine made on a small scale with minimal manipulation is less predictable in its quality, but this is because it is more distinctive, an expression of grapes that were grown in a particular place and year, and transformed by a particular winemaker. Such wine is more expensive than industrial wine, sometimes much better, and usually more interesting.

Wine Grapes

Grapes provide the substance of wine, and therefore determine many of its qualities. Their most important components are

• Sugars, which the yeasts feed on and convert into alcohol. Wine grapes are generally harvested with 20–30% sugar, mainly glucose and fructose.
• Acids, mainly tartaric and some malic, which help prevent the growth of undesirable microbes during fermentation, and are a major component of wine flavor.
• Tannins and related phenolic compounds, which contribute an astringent feeling and thereby a body and weightiness to wine (p. 737).
• Pigment molecules that provide color, and sometimes contribute to astringency as well. Red grapes contain anthocyanin pigments (p. 267), mainly in the skins. “White” grapes lack anthocyanins; their yellowish color comes from a different group of phenolic compounds, the flavonols.
• Aroma compounds, which may be generically grapey, or distinctive of a particular grape variety. Many aromatics are chemically bound to other molecules, often sugars, and so aren’t evident in the raw fruit; during winemaking, fruit and yeast enzymes liberate the aromatics and so make them available for us to enjoy.

Grape Varieties and Clones The grapevine evolved with the ability to regenerate itself and grow vigorously in the spring. It’s easily propagated by cuttings, and readily lends itself to creating identical versions, or clones of a given plant. And it’s a variable species, one that offers many differences in growth habit, requirements for water and temperature, and fruit composition. For several millennia, and until around 1800, grapes were mostly cultivated and made into wine throughout western Asia and Europe by small groups of people essentially isolated from each other and living in different environments. So there developed a large number of distinctive grape varieties, each selected by particular people for characteristics they found desirable.

Today it’s estimated that there are around 15,000 different varieties of the Eurasian grape, Vitis vinifera. A single variety — Pinot Noir, for example, or Cabernet Sauvignon — may exist in the form of several hundred different clones, each a somewhat different version of that variety. Some varieties have very distinctive aromas; others are more subtle or even anonymous and therefore allow the aromas of the fermentation and aging more prominence. The term noble is applied to varieties that produce wines with the potential for developing great complexity over many years in the bottle; these include the French Cabernet Sauvignon, Pinot Noir, and Chardonnay, the Italian Nebbiolo and Sangiovese, and the German Riesling.

The Influence of Growing Conditions; Vintage and “Terroir”

Pampered Vines Don’t Make the Best Wines As Pliny observed 2,000 years ago, “the same vine has a different value in different places.” The quality of grapes, and of the wine made from them, is influenced by the conditions in which the grapes grow and mature. To produce a decent wine, the grapes must ripen to an adequate sweetness, and so the vine must get enough sun, warmth, minerals, and water. On the other hand, abundant water produces watery fruit, abundant soil nitrogen produces excess foliage that shades the fruit and gives it odd flavors, and abundant sun and warmth produce fruit with plenty of sugar but reduced acidity and aroma compounds, and thus a strong but flat wine.

Vintage Wines The grapes that make the best wines seem to be produced in a narrow range of conditions — barely adequate water, minerals and light and heat — that encourage complete but slow, gradual ripening. Those conditions may or may not be realized in a given year. Hence the significance for many wines of the vintage, the particular year in which the grapes are grown and harvested. Some years yield better wines than others.

Terroir In recent times, much has been said and written about the importance in winemaking of terroir: the influence on a wine of the particular place in which the grapes were grown. The French word includes the entire physical environment of the vineyard: the soil, its structure and mineral content; the water held in the soil; the vineyard’s elevation, slope, and orientation; and the microclimate, the regime of temperature, sunlight, humidity, and rainfall. Each of these aspects can vary over small distances, from one vineyard to the next; and each can affect the growth of the vine and the development of its fruit, sometimes in indirect ways. For example, sloping ground and certain kinds of soil encourage water to drain away from the roots, and absorb and release the sun’s heat to the vine in different ways. A south-facing slope can increase the exposure to autumn sunlight by 50% over a planting on level ground, and thus extend the growing season and accumulation of flavor compounds.

The wine connoisseur enjoys detecting and marveling at the expression of terroir in wines, the palpable differences in the wines made from neighboring vineyards. The winemaker, on the other hand, generally tries to manage and minimize the effects of less than ideal terroirs and vintages. There’s nothing new about this effort to make the best of things. The French have been adding sugar to their fermenting grapes for centuries to compensate for incomplete ripening. What’s new nowadays is the degree to which the grape composition can be manipulated after harvest, so that the wine becomes less the product of a particular place and year, and more the product of modern fermentation technology.

Making Wine

The making of a basic table wine can be divided into three stages. In the first, the ripe grapes are crushed to free their juice. In the second, the grape juice is fermented by sugar-consuming, alcohol-producing yeasts into new wine. The third stage is the aging or maturing of the new wine. This is a period during which the chemical constituents of the grape and the products of fermentation react with each other and with oxygen to form a relatively stable ensemble of flavor molecules.

Crushing Grapes to Make the Must Crushing extracts from the grape the liquid that will become wine. This step therefore determines to a large extent the final wine’s composition and potential qualities.

The substances important to wine quality are not evenly distributed in the grape. The stems contain bitter-tasting resins and are usually separated from the grapes as they are crushed. The skin holds much of the fruit’s phenolic compounds, both pigments and tannins, as well as most of the acid and the many compounds that give the grape its characteristic aroma. Like the stem, the seeds at the center are full of tannins, oils, and resins, and care is taken not to break them open during the pressing.

As a mass of grapes is crushed in a mechanical press, the first juice to come out, the free run, is primarily from the middle of the pulp, and is the clearest, purest essence of the grape, sweet and largely tannin free. As mechanical pressure is applied, juices from just under the skin and around the seeds augment the free run with a more complex character. The extent of pressing will have an important influence on the character of the final wine. The liquid portion, called the must, is 70 to 85% water, 12 to 27% sugars, mainly glucose and fructose, and about 1% acids.

Fruits of the grape vine, Vitis vinifera. The different regions of the grape contain different proportions of sugar, acid, and other flavor components.

After the Crush In the case of white wines, the must is left in contact with the skins for a few hours and removed with gentle pressure before fermentation. It thus picks up little tannic material or pigmentation. Rosé musts and red wine musts are partly fermented in contact with the red skins. The longer the must is in contact with skin and seeds, and the harder it is pressed, the deeper the color (whether yellow or red) and the more astringent the taste.

Before beginning the fermentation, the winemaker usually adds two substances to the must. One, sulfur dioxide, suppresses the growth of undesirable wild yeasts and bacteria, and prevents the oxidation of both flavor and pigment molecules (the same treatment is given to many dried fruits, and for the same reason). Though this treatment may sound antiseptically modern, it is centuries old. One of the natural by-products of fermentation that is increased by sulfuring is sulfites, sulfur compounds that can induce an allergic reaction in sensitive people.

The second additive is either sugar or acid, and it is used to correct the balance between these two substances. Grapes that ripen in a cool climate can lack the sugar to produce enough alcohol for a stable wine; grapes that ripen in a hot climate metabolize some of their acids and can produce a flat-tasting wine. French winemakers usually add sugar; California winemakers often add tartaric acid.

The Alcoholic Fermentation

The Fermentation Yeasts Fermentation can begin with or without the addition of a starter culture of yeast. The winemaker can choose among many different strains of Saccharomyces, or allow the fermentation to begin spontaneously with “wild” yeasts from the grape skins (species of Kloeckera, Candida, Pichia, Hansenula, and others). These are always eventually displaced by Saccharomyces cerevisiae, which has a greater tolerance for alcohol, but they do contribute flavor compounds to the finished wine.

The primary job of the yeast is to convert sugar to alcohol, but it also produces various volatile, aromatic molecules that the grape itself cannot supply. Prominent among them are the longer-chain alcohols, and esters, a class of compounds that combine an acid with an alcohol or phenol. Both yeast and grape enzymes and the acid conditions also liberate aromatic molecules from the nonvolatile sugar complexes in which some are stored in the grape, so fermentation also brings out the grape’s own flavor potential.

Temperatures and Times The winemaker varies the conditions of fermentation according to the particular kind of wine being made. In the case of delicate white wines, the must is fermented for four to six weeks at about 60ºF/16ºC. With more robust red wines, the must is fermented at a temperature between 65 and 80ºF/18–27ºC in contact with the skins, to extract pigments, tannins, and flavor. This phase may last for 4 to 14 days (less if heat or a carbon dioxide treatment is applied). Then the must is separated from the skins and fermented again for a total of two to three weeks. One of the most critical variables during fermentation is temperature. The lower the temperature, the slower and longer the fermentation, and the more aromatic molecules accumulate.

The main fermentation is considered complete when essentially all the sugar in the must has been converted into alcohol. A wine with no residual sugar is called dry. Sweet wines are made by stopping the fermentation before all the sugar has been consumed, or more commonly, by adding some reserved sweet grape juice to the dry wine after its yeast has been removed.

OPPOSITE: Making red and white wines. White wines are fermented at a lower temperature and without the grape skins and seeds; they’re also clarified at a lower temperature, in part so that they won’t cloud when served chilled.

Malolactic Fermentation Winemakers sometimes allow or even induce a second bacterial fermentation in the new wine after the main yeast fermentation. The bacterium Leuconostoc oenos consumes the wine’s malic acid and converts it into lactic acid, which is less strong and sour. This “malolactic” fermentation thus reduces the apparent tartness of the wine. It also produces a number of distinctive aroma compounds, among them buttery diacetyl. (A relative of L. oenos, L. mesenteroides, contributes the same compound to cultured butter itself!) Some winemakers work to prevent a spontaneous malolactic fermentation from developing, so that they can retain the sharpness and flavor of the original wine.

Maturation Once fermentation is complete, the new wine is drained out of the fermentation tanks to begin the work of clarification and aging, in which the cloudy, rough-tasting liquid develops into a clear, smooth one.

Racking and Fining The solid particles of grape and yeasts are cleared from the wine by the process of racking: letting the yeast cells and other large particles settle, carefully drawing the wine off the sediment into a new container, and repeating the process every few months. Interesting exceptions to this rule are wines intentionally aged for months or even years sur lie, or “on the lees,” in contact with the yeast sediment, whose cells slowly break apart and contribute more flavor and body to the wine. Champagne and Muscadet are two wines that are aged on the lees.

The cool racking temperatures — less than 60ºF/16ºC for red wines, around 32ºF/0ºC for whites — reduce the solubility of all the dissolved solids, and cause the wine to cloud up with a fine precipitate of various complexes of proteins, carbohydrates, and tannins. Late in the racking procedure, the wine may be fined: that is, a substance will be added to the wine that attracts these suspended particles to itself, and then settles to the bottom, carrying them with it. Gelatin, egg white, bentonite clay, and synthetic materials are used. Any particles remaining in the wine after racking and fining can be removed by passing it through a centrifuge or filter. Winemakers may choose to limit or omit the fining and filtration steps, since they remove some flavor and body along with the undesirable particles.

Barrel Aging New wine has a raw flavor and a strong, simple, fruity aroma. As the wine rests after fermentation, a host of chemical reactions slowly proceeds, and results in the development of balance and complexity in the flavor. If the wine is being held in a new wood barrel, it also absorbs various substances from the wood that either provide flavor directly — for example, vanilla-like vanillin and the coconut-woody oak lactones — or that modify the wine’s own flavor molecules. In traditional winemaking, the months during which the wine is racked and shifted from container to container are a time when the wine’s chemical evolution is directed by periodic exposure to the air. In the presence of oxygen, the tannins, anthocyanin pigments, and other phenolic compounds react with each other to form large complexes, so the wine’s astringency and bitterness decline. Some of the molecules that provide aroma break apart or react with oxygen and each other to form a new suite of aromas, so fruity, floral notes fade in favor of a more subdued general “wineyness.” White and light red wines are generally bottled young, after 6–12 months, with a fairly fresh, fruity bouquet, while astringent dark reds may require a year or two to develop and smooth out.

Most wines are made by blending two or more different varieties, and this important test of the winemaker’s art occurs just before bottling. The final wine may then be filtered to remove any remaining microbes and haze, and given a final dose of sulfur dioxide to prevent microbial growth during storage. It may also be pasteurized. This practice is not limited to inexpensive wines. The Burgundy wines of Louis Latour are flash-heated for 2–3 seconds at 165ºF/72ºC, a treatment that is said not to have a detrimental effect on the wine’s continuing flavor development.

Bottle Aging After a period of a few months to two years in barrels or tanks that allow controlled contact with oxygen, the wine goes into impermeable glass bottles. For the last two centuries, the standard stopper for wine bottles has been cork, which is made from the bark of a species of oak. Because cork can be the source of off-flavors, some wine producers are now using metal and plastic stoppers (see box below).

Wine continues to be affected by oxidation long after it leaves the cask. It picks up some air when it is filled into the bottle, and the bottle is sealed with a small space between wine and cork. So while oxidation is greatly slowed in the bottle, it does continue, though it may be outweighed by a different set of reactions, “reductive” rather than oxidative. The chemical changes that occur are not well understood, but include the ongoing liberation of aromatic molecules from nonaromatic complexes, and aggregation reactions among tannins and pigments that further lower astringency and cause a shift in pigment hues, usually toward the brown.

White wines and light-red rosés benefit from about a year of bottle aging, during which time the aroma develops and the amount of free, odorous sulfur dioxide decreases. Many red wines improve greatly after a year or two in the bottle, and some may develop for decades. All wines have a finite life span, and their quality eventually declines. White wines develop overtones of honey, hay, wood, and chemical solvents; red wines lose much of their aroma and become flat-tasting and more plainly and harshly alcoholic.

Special Wines

In the last few pages, I’ve described the general method for making dry table wines, which usually accompany meals. Sparkling, sweet, and fortified wines are often sipped on their own. Here is a brief account of their special qualities and how they are produced.

Sparkling Wines: Champagne and Others Sparkling wines delight by emitting bubbles that catch the light and prick the tongue. The bubbles come from the wine’s considerable dissolved reserves of carbon dioxide gas, a by-product of yeast metabolism that ordinarily escapes into the air from the surface of the fermenting wine. To make a sparkling wine, the wine is confined under pressure — either in the bottle or in special tanks — so that the carbon dioxide can’t escape as it’s produced, and instead comes to saturate the liquid. A bottle of Champagne holds a gas pressure of 3–4 atmospheres, somewhat higher than the pressure in car tires, and contains about six times its volume in carbon dioxide!

When we remove the cork and thus relieve the pressure, the excess carbon dioxide leaves the solution in the form of gas bubbles. The bubbles form wherever the liquid comes into contact with a microscopic air pocket into which the dissolved carbon dioxide can diffuse. In the glass, the bubbles form on scratches and other surface imperfections. The refreshingly sharp prickle in the mouth comes from the irritating dose of carbonic acid that the bubbles deliver as they redissolve into the unsaturated layer of saliva.

Many countries have their own versions of sparking wine, which range from the carefully crafted to the mass-produced. The best-known example of a sparkling wine is Champagne, which strictly speaking is the wine made in the region of that name east of Paris, and accounts for less than a tenth of the world’s production of sparkling wine. From the late 17th century to the late 19th, Champagne evolved to become the most refined expression of this style. The French invented the method of inducing a bubble-making second fermentation in the bottle, and this méthode champenoise has become a worldwide benchmark for making fine sparkling wines.

Making Champagne The first stage in making Champagne is to produce a base wine, which is made primarily from Pinot Noir and/or Chardonnay grapes. Next comes the secondary fermentation, which must be carried out in a closed container in order to retain the gas. Sugar is added to the dry base wine as food for the yeast. The wine, sugar, and yeast are put into individual bottles, corked, clamped, and kept at about 55ºF/13ºC.

Though the secondary fermentation is usually complete after about two months, the wine is left to age in contact with the yeast sediment for anywhere from a few months to several years. During this time, most of the yeast cells die, fall apart, and release their contents into the wine, giving it a distinctive, complex flavor with toasted, roasted, nutty, coffee, even meaty notes (due in large part to complex sulfur compounds). In addition to flavor, yeast proteins and carbohydrates will stabilize bubbles when they form in the glass, and help produce the very fine bubbles typical of Champagne. After aging on the yeast, the sediment is removed and the bottle topped off with additional wine, and finished with a small amount of aged wine mixed with sugar and brandy. The bottle is then recorked.

Making Other Sparkling Wines The traditional Champagne process is labor intensive, time consuming, and expensive. More affordable and less complex sparkling wines are made all over the world in a number of different ways. One is simply to minimize or eliminate aging on the yeast sediment. Others involve fermenting the base wine for the second time not in individual bottles, but in large tanks, or not fermenting again at all: the cheapest sparkling wines are simply carbonated as soft drinks are, with tanks of pressurized carbon dioxide.

Sweet Wines Table wines are generally fermented until they are dry: that is, until the yeast consumes essentially all the grape’s sugars and converts them into alcohol. Sweet or dessert wines with 10–20% “residual” sugar are made in several different ways:

• An ordinary dry wine is sweetened with some unfermented grape juice, and the combination treated to prevent further fermentation with a dose of sulfur dioxide, or filtration that removes all yeast and bacteria from the wine.
• Grapes are dried on the vine or after picking to concentrate their sugars to 35% or more of the grape weight. This leaves residual sugar in the wine when the yeasts reach their maximum alcohol level and the fermentation stops. German Trockenbeerenauslese and Italian recioto wines are examples.
• Grapes are left on the vine past the first frost and picked when frozen (or frozen artificially), and then gently pressed while cold to separate the concentrated juice from the ice crystals. The concentrated juice ferments into a stable wine with residual sugar. German Eiswein dates from around 1800.
• The grapes are allowed to become infected with “noble rot,” the mold Botrytis cinerea, which dehydrates the grapes, concentrates their sugars, and transforms their flavor and consistency. This method originated in the Tokaji region of Hungary around 1650, and was adopted in the German Rheingau by 1750 and in the Sauternes region of Bordeaux around 1800.

The Noble Rot: Tokaji, Sauternes, and Others The noble rot (French pourriture noble, German Edelfäule)Botrytis cinerea is also known as bunch rot, and it is mainly a destructive disease of grapes and other fruits. It becomes noble only in the right climatic conditions, when the initial infection in humid weather is followed by a dry period that limits the infection. In this situation, the mold does several useful things. It perforates the skin of the grape, thus allowing it to lose moisture and become concentrated during the subsequent dry period; it metabolizes some of the tartaric acid at the same time that it consumes some of the grape’s sugars, so the balance between sweetness and acidity doesn’t suffer; it produces glycerol, which lends the eventual wine an incomparably dense body; and it synthesizes a number of pleasing aroma compounds, notably the maple-sugar-like sotolon, mushroomy octenol, and a number of terpenes. The honeyed flavor of these wines can develop in the bottle for decades.

Fortified Wines Fortified wines are so called because the strength of the base wine is boosted by the addition of distilled spirits to 18–20% alcohol, a level that prevents spoilage by vinegar bacteria and other microbes. Fortification appears to have begun in the sherry-producing region of Spain sometime before 1600. Winemakers take advantage of the stability of fortified wines by exposing them to the air for months or years. They thus make a virtue of the normally undesirable oxidative changes in flavor that come with keeping leftover wine. Most fortified wines keep well for weeks in an opened bottle or decanter.

Madeira Beginning in the 15th century, Portuguese ships embarking on long voyages to the Indies would pick up barrels of ordinary wine on the Portuguese island of Madeira. Sailors and producers soon found that the long barrel aging in extreme temperatures and with constant agitation produced an unusual but attractive wine. By 1700, ships were sailing to the East Indies and back just to age the barrels of Madeira stored on board; by 1800, the wine was being fortified with brandy and hot-aged on the island. Today, the base wine, which can be white or red, is fortified, sometimes sweetened, then artificially heated to a temperature around 120ºF/50ºC, where it’s held for three months before slowly cooling down again. It’s then aged in barrels in a sherry-like solera system (below) before bottling. There are several different styles of Madeira, from sweet to nearly dry.

Port The name port was originally the English term for any Portuguese wine. The addition of brandy was introduced in the 18th century as a way of guaranteeing that the wines would get to England in drinkable condition, and it resulted in the development of an unusual group of sweet red wines. Port is made by stopping the fermentation of the base red wine while about half the grape sugar is left, and fortifying it with distilled spirits to give an alcohol content around 20%. The wine is then aged in barrel and finally in bottle for anywhere from two to 50 years. Older ports are characterized by the maple-like compound sotolon and other sweetly aromatic compounds, likely products of browning reactions, which are also found in botrytized wines and sherries.

Sherry Sherry is a fortified, oxidized white wine that was developed in the Spanish port city Jerez de la Frontera, whose name was Anglicized to “sherry” around 1600. True sherry gets its distinctive flavor from the solera system of maturing wine, which was developed early in the 19th century. The solera is a series of casks, each initially containing the fortified new wine of a particular year, but not completely filled, so a significant area of wine surface is in direct contact with the air. The wine therefore develops a characteristic intense, oxidized flavor. As the cask contents evaporate and become more concentrated, each is replenished with wine from the next younger cask. The final wine is bottled from the casks containing the oldest wines, and thus is a blend of wines from many different vintages and degrees of development.

There are a variety of rapid industrial methods for making sherry-like wines. The fortified base wines may be heated to develop the flavor, or cultured with a “submerged flor”: the wine and flor yeasts (see box) are kept in large tanks and agitated and aerated.

Vermouth Modern-day vermouth derives from a medicinal wine made in 18th-century Italy, which the Germans named Vermut after its main ingredient, wormwood (see box, p. 771). Today it’s essentially a flavored wine fortified to about 18% alcohol, used mainly in mixed drinks and in cooking. Vermouth is made in both Italy and France from a neutral white wine flavored with dozens of herbs and spices, and sometimes sweetened (up to 16% sugar). The French usually extract the flavorings in the wine itself, while the Italians extract or co-distill them with the fortification alcohol. Once fortified, the wine is aged for several months.

Storing and Serving Wine

Wine Storage Wines are sensitive liquids, and require some care in order to keep well and even improve during storage. They’re best kept in some version of the traditional cellar: a moderately humid, dark, cool place. Bottles are stored on their sides, so that the wine wets the cork and prevents it from drying out, shrinking, and allowing air in. Moderate humidity keeps the outer portion of the cork from shrinking, and constant temperature prevents volume and pressure changes in the liquid and air inside the bottle, which can cause air and wine movement in the space between bottle and cork. Darkness minimizes the penetration of high-energy light into sparkling and other white wines, where it can cause a sulfury off-aroma similar to that found in light-struck beer and milk (pp. 749, 21). And low temperatures, between 50 and 60ºF/10–15ºC, slow the wine’s development, so that it remains complex and interesting for the longest possible time.

Serving Temperatures Different kinds of wine taste their best at different serving temperatures. The colder a wine, the less tart, sweet, and aromatic it seems. Intrinsically tart and mildly aromatic wines, usually light white and rosé wines, are best served cold, 42–55ºF/5–13ºC. Less tart, more aromatic red wines are more full-flavored at 60–68ºF/16–20ºC. The strongly alcoholic, richly aromatic port is said to taste best at 65–72ºF/18–22ºC. Complex white wines may be served at higher temperatures than their light cousins; similarly, many light red wines are better at cooler temperatures.

“Breathing” and Aeration Wines can sometimes be improved just before serving by a period of aeration or “breathing.” Such a treatment allows volatile substances in the wine to escape into the air, and it allows oxygen from the air to enter the wine, where it reacts with volatile and other molecules and changes the wine’s aroma. No significant aeration occurs when a wine is simply uncorked and left to sit in the open bottle. The most effective way to aerate a wine is to pour it, and into a broad, shallow decanter that continues to expose a large surface area to the air. Aeration can improve a wine’s aroma by accelerating the escape of some off-odors (for example, excess sulfur dioxide in some white wines), and by providing a kind of accelerated aging to young, undeveloped red wines. But it allows desirable aromas to escape as well, and can undo the complexity of a mature wine that has developed slowly over years in the bottle.

Wine also absorbs oxygen when it’s poured into the glass and as it rests there, and its aroma often evolves noticeably between the first sip and the last. To discover this dynamic quality and follow its course is one of the pleasures of drinking wine.

Keeping Leftovers The key to preserving the quality of leftover wine is to minimize chemical change. Lowering the wine’s temperature slows all chemical activity, and simple refrigeration works well for white wines, which usually keep well simply by being recorked and refrigerated. However, chilling causes dissolved substances in more complex red wines to precipitate into solid particles, and this causes irreversible changes in flavor. Leftover red wine is best handled by a minimizing its exposure to flavor-altering oxygen, which can be done by means of inexpensive devices that pull the air out of a partly empty bottle, or by replacing the air with inert nitrogen gas, or by gently pouring a partial bottle into smaller bottles that can be filled all the way to the top — though the act of pouring itself introduces some air into the wine.

Enjoying Wine

For those who love it, wine can be endlessly fascinating. The varieties of grape, the place they were grown in, the weather that year, the yeasts that ferment them, the skills of the winemaker in handling them, the years they spend in oak or in glass: all these factors and more affect what we taste in a sip of wine. And there’s a lot to taste in that sip, because wine has one of the most complex flavors of all our foods. Wine connoisseurs have developed an elaborate vocabulary to try to capture and describe these fugitive sensations, one that may seem forbiddingly complicated and fanciful. Many of us most of the time would be content with the five F’s proposed 800 years ago in the Regimen of Health for the School of Salerno:

Si bona vina cupis, quinque haec laudantur in illis:

Fortia, formosa, et fragrantia, frigida, frisca.

If you desire good wines, these five things are praised in them:

Strength, beauty, and fragrance, coolness, freshness.

On the other hand, we can learn to taste much more in a sip of wine, and get more pleasure from it, if we know something about what’s in that sip, about the kinds of substances that can and do contribute to the flavor of wine (see box, p. 738).

Clarity and Color The appearance of a wine can give some important clues about how it will taste. If the wine is cloudy and the particles don’t settle with a few hours’ standing, it has probably undergone an unintended bacterial fermentation in the bottle, and its flavor is likely to be off. Tiny crystals (which do settle) are usually salts of excess tartaric or oxalic acid, and are not signs of spoilage; in fact they indicate a good level of acidity. “White” wines actually range in color from straw yellow to deep amber. The darker the color, the older the wine — the yellow pigments turn brownish when oxidized — and the more mature the flavor. Most red wines retain a deep, ruby-like color for some years, along with a fruity character in the flavor. As they age, the anthocyanin pigments complex with some of the tannins and precipitate, leaving more of the brownish tannins visible. The wine develops an amber or tawny tint, which goes along with its less fruity, more complex flavor.

Feeling and Taste in the Mouth When we experience a sip of wine in the mouth, the senses of both touch and taste come into play.

Astringency The feel of a wine is largely a matter of its astringency and viscosity. Astringency — the word comes from the Latin for “to bind together” — is the sensation we have when the tannins in wine “tan” the lubricating proteins in our saliva the way they do leather: they cross-link the proteins and form little aggregates that make the saliva feel rough rather than slick. This dry, constricting feeling, together with the smoothness and viscosity caused by the presence of alcohol and other extracted components, and in sweet wines sugar, create the impression of the wine’s body, of substance and volume. In strong young red wines, the tannins can be palpable enough that “chewy” seems a good description. In excess, they are drying and harsh.

Taste The taste of a wine is mostly a matter of its sourness, or a balance between sour and sweet, and a savory quality that has been attributed to succinic acid and other products of yeast metabolism. Phenolic compounds can sometimes contribute a slight bitterness. The acid content of a wine is important in preventing it from tasting bland or flat; it’s sometimes said to provide the “backbone” for the wine’s overall flavor. White wines are usually around 0.85% acid, red wines 0.55%. Wines that are fermented dry, with no residual sugar, may still have a slight sweetness thanks to the alcohol and glycerol, a sugar-like molecule produced by the yeasts. Fructose and glucose are the predominant sugars in grapes, and they begin to provide a noticeable sweetness when left in wines at levels around 1%. Sweet dessert wines may contain more than 10% sugars. In strong wines, alcohol itself can dominate other sensations with its pungent harshness.

Wine Aroma If acidity is the backbone of a wine, viscosity and astringency its body, then aroma is its life, its animating spirit. Though they account for only about one part in a thousand of wine’s weight, the volatile molecules that can escape the liquid and ascend into the nose are what fill out its flavor, and make wine much more than tart alcoholic water.

An Ever-Changing Microcosm A given wine contains several hundred different kinds of volatile molecules, and those molecules have many different kinds of odors. In fact they run the gamut of our olfactory world. Some of the same molecules are also found in temperate and tropical fruits, flowers, leaves, wood, spices, animal scents, cooked foods of all kinds, even fuel tanks and nail polish remover. That’s why wine can be so evocative and yet so hard to describe: at its best, it offers a kind of sensory microcosm. And that little world of molecules is a dynamic one. It evolves over months and years in the bottle, by the minute in the glass, and in the mouth with every passing second. The vocabulary of wine tasting thus amounts to a catalogue of things in the world that can be smelled, and whose smell can be recognized, however fleetingly, in an attentive sip.

A few of the aromatic substances in wine are contributed directly by particular varieties of grape, mainly the flowery terpenes of some white grapes and unusual sulfur compounds in the Cabernet Sauvignon family. But the primary creators of wine aroma are the yeasts, which apparently generate most of the volatile molecules as incidental by-products of their metabolism and growth. The yeasts and 400 generations of winemakers, who noticed and cultivated those incidental pleasures, made a tart alcoholic liquid into something much more stimulating.

Beer

Wine and beer are made from very different raw materials: wine from fruits, beer from grains, usually barley. Unlike grapes, which accumulate sugars in order to attract animals, the grains are filled with starch to provide energy for the growing embryo and seedling. Yeasts can’t exploit starch directly, and this means that before they can be fermented, grains must be treated to break down their starch to sugars. While it’s true that grapes are much more easily fermented — yeasts begin to flourish in the sweet juice as soon as they break open — grain has several advantages as a material for producing alcohol. It’s quicker and easier to grow than the grapevine, much more productive in a given acreage, can be stored for many months before being fermented, and it can be made into beer any day of the year, not just at harvest time. Of course grains bring a very different flavor to beer than grapes do to wine; it’s the flavor of the grasses, of bread, and of cooking, which is essential to the beer-making process.

The Evolution of Beer

Three Ways to Sweeten Starchy Grains Our ingenious prehistoric ancestors discovered no fewer than three different ways to turn grains into alcohol! The key to each was enzymes that convert the grain starch into fermentable sugars. Because every enzyme molecule can do its starch-splitting operation perhaps a million times, a small quantity of the enzyme source can digest a large quantity of starch into fermentable sugars. Inca women found the enzymes in their own saliva: they made chicha by chewing on ground corn, then mixing that corn with cooked corn. In the Far East, brewers found the enzymes in a mold, Aspergillus oryzae, which readily grew on cooked rice (p. 754). This preparation, called the chhü in China, koji in Japan, was then mixed with a fresh batch of cooked rice. In the Near East, the grain itself supplied the enzyme. Brewers soaked the grain in water and allowed it to germinate for several days, then heated the ground seedling with ungerminated grain. This technique, called malting, is the one most widely used today to make beer.

Beer in Ancient Times Malting is much like the making of sprouts from beans and other seeds, and may have begun in the sprouting of grains simply to make them softer, moister, and sweeter. There’s clear evidence that barley and wheat beers were being brewed in Egypt, Babylon, and Sumeria by the third millennium BCE, and that somewhere between a third and half of the barley crop in Mesopotamia was reserved for brewing. We know that brewers preserved the malted grain, or malt, by baking it into a flat bread, then soaked the bread in water to make beer.

The knowledge of beer making seems to have passed from the Middle East through western Europe to the north, where in a climate too cold for the vine, beer became the usual beverage. (Among the nomadic tribes of northern Europe and central Asia who did not even cultivate grain, milk was fermented into the drinks called kefir and koumiss.) To this day, beer remains the national beverage of Germany, Belgium, Holland, and Britain.

Wherever both have been available, beer has been the drink of the common people and wine the drink of the rich. The raw material for beer, grain, is cheaper than grapes and its fermentation is less tricky and drawn out. To the Greeks and Romans, beer remained an imitation wine made by barbarians who did not cultivate the grape. Pliny described it as a cunning if unnatural invention:

Germany: Hops and Lagering In the centuries following the fall of Rome, beer continued to be an important beverage in much of Europe. Monasteries brewed it for themselves and for nearby settlements. By the 9th century, alehouses had become common in England, with individual keepers brewing their own. Until 1200, the English government considered ale to be a food, and did not tax it.

It was in medieval Germany that two great innovations made beer largely what it is today: brewers preserved and flavored it with hops, and began to ferment it slowly in the cold to make mild-flavored lager.

Hops The earliest brewers probably added herbs and spices to beer, both to give it flavor and to delay the development of off-flavors from oxidation and the growth of spoilage microbes. In early Europe this mixture, called gruit in German, included bog-myrtle, rosemary, yarrow, and other herbs. Coriander was also sometimes used, juniper in Norway, and sweet gale (Myrica gale) especially in Denmark and Scandinavia. It was around 900 that hops, the resinous cones of the vine Humulus lupulus, a relative of marijuana, came into use in Bavaria. Thanks to its pleasant taste and effectiveness in delaying spoilage, it had largely replaced gruit and other herbs by the end of the 14th century. In 1574, Reginald Scot noted in A Perfite Platforme of a Hoppe Garden that the advantages of hops were overwhelming: “If your ale may endure a fortnight, your beer through the benefit of the hops, shall continue a month, and what grace it yieldeth to the taste, all men may judge that have sense in their mouths.” Still, it was not until about 1700 that English ale was hopped as a matter of course.

Lager From the times of Egypt and Sumeria to the Middle Ages, brewers made beer without much control over the temperature of fermentation, and with yeasts that grew at the surface of the liquid. The beer fermented in a few days, and it was consumed within days or weeks. Sometime around 1400, in the foothills of the Bavarian Alps, there evolved a new kind of beer. It was fermented in cool caves over the period of a week or more, and with a special yeast that grew below the surface of the liquid. Then it was packed in ice for several months before it was drawn off the yeast sediment for drinking. The cool, slow fermentation gave the beer a distinctive, relatively mild flavor, and the cold temperature and long settling time produced a sparkling-clear appearance. This lager beer (from the German lagern, “to store,” “to lay down”) remained distinctly Bavarian until the 1840s, when the special yeast and techniques were taken to Pilsen, Czechoslovakia, to Copenhagen, and to the United States, and became the prototype of most modern beers. England and Belgium are the only major producers that still brew most of their beer in the original way, at warm temperatures and with top-fermenting yeasts.

England: Bottles and Bubbles, Specialty Malts The English were late to accept hops, but pioneered in the making of bottled beer. Ordinary ale — the original English word for beer — was fermented in an open tank, and like wine it lost all its carbon dioxide to the air: the bubbles simply rose to the surface and burst. Some residual yeast might grow while the liquid was stored in a barrel, but it would lose its light gassiness as soon as the barrel was tapped. Sometime around 1600, it was discovered that ale kept in a corked bottle would become bubbly. Quite early on, the discovery was attributed to Alexander Nowell, dean of St. Paul’s Cathedral. Thomas Fuller, in his 1662 History of the Worthies of England, wrote:

By 1700, glass-bottled ale sealed with cork and thread had become popular, along with sparkling Champagne (p. 724). But both were largely novelties. Most beer was drunk flat, or close to it, from barrels. Centuries later, with the development of airtight kegs, of carbonation, and the increasing tendency to drink beer at home instead of at the tavern, bubbly beer became the rule.

Specialty Malts The 18th and 19th centuries were an innovative time in Britain, and it was early in this period that many of today’s familiar British brewing names — Bass, Guinness, and others — got their start. By 1750, the greater control that coke and coal heat gave the maltster made gently dried pale malts possible, and thereby pale ales. And in 1817, “patent malt” was developed. This was malted barley roasted very dark, and used in small amounts only to adjust the color and flavor of ales and beers, not to provide fermentable sugars. Patent and pale malts made it possible to produce a range of dark beers with a combination of light, largely fermentable malt and very dark coloring malt. This was the beginning of porter and stout as we know them today: darker and heavier than ordinary brews, but much lighter and less caloric than they were 200 years ago.

Beer in America The U.S. preference for light, even characterless brews would seem to be the result of climate and history. Heavy beer is less refreshing when the summers get as hot as ours do. And the original British colonists seem to have been more interested in making whiskey than beer (p. 760). We had no strong national tradition in the matter of beer, so the way was clear for later German immigrants to set the taste around 1840, when someone — perhaps one John Wagner near Philadelphia — introduced the newly available lager yeast and technique, and the distinctive brew caught on.

Both Milwaukee and St. Louis quickly became centers of lager brewing: in the former, Pabst, Miller, and Schlitz; in the latter, Anheuser and Busch; and Stroh in Detroit all got their starts in the 1850s and 1860s, and Coors in Denver in the 1870s. Several of these names and their light, Pilsner-style beers remain dominant today, while the stronger traditional brews of England and Germany appeal to a relatively small number of beer lovers. The only indigenous American style of beer is “steam beer,” a rare relic of the California Gold Rush. Without the large supply of ice necessary to make lager beer, San Francisco brewers used the yeast and techniques appropriate to cool bottom fermentation, but brewed at top-fermentation temperatures. The result: a full-flavored and gassy beer that gave off a lot of foam when the keg was tapped.

Beer Today Today, the countries with the largest per capita consumption of beer are mainly traditional European beer producers: Germany, the Czech Republic, Belgium, and Britain and its former colony Australia. In the United States, beer accounts for more than three quarters of the alcoholic drinks consumed. Most American beer remains bland and uniform, produced by a handful of large companies in largely automated factory-like breweries. The 1970s brought a revival of interest in more flavorful alternatives, and a flourishing of “microbreweries” making specialty beers in small quantities, brewpubs that both brew and serve beer, and home brewing. Some of these small enterprises have grown with their success, and the giant brewers are now making microbrew lookalikes. And it’s now possible to find beers from all over the world in liquor stores and supermarkets. These are good times for exploring the many different styles of beer and ale.

Brewing Ingredients: Malt

Beer begins with barley. Other grains — oats, wheat, corn, millet, sorghum — have also been used, but barley has become the grain of choice because it’s the best at generating starch-digesting enzymes.

Malting The first step in converting barley grain into malt is to steep the dry grain in cool water and then allow it to germinate for several days at around 65ºF/18ºC. The embryo restarts its biochemical machinery and produces various enzymes, including some that break down the barley cell walls, and others that break down the starch and proteins inside the cells of the food-storage tissue, the endosperm. These enzymes then diffuse from the embryo into the endosperm, where they work together to dissolve away the cell walls, penetrate the cells, and digest some of the starch granules and protein bodies inside. The embryo also secretes the hormone gibberellin, which stimulates the aleurone cells to produce digestive enzymes as well.

The maltster’s aim is to maximize the breakdown of the endosperm cell walls and the grain’s production of starch-and protein-digesting enzymes. The cell walls have been adequately weakened by the time that the growing tip of the embryo reaches the end of the kernel, some five to nine days after the grain is first soaked. If the maltster is going to make a pale malt, then he keeps starch digestion to a minimum and malts for a shorter time; for a darker malt that will benefit from more sugars for the browning reactions, he malts for a longer time, and may finish by holding the moist barley at 140–180ºF/60–80ºC to maximize the action of the starch-digesting, sugar-producing enzymes.

Kilning Once the barley reaches the desired balance of enzymes and sugars, the maltster fixes that balance by drying and heating it in a kiln. The dehydration and heat kill the embryo, and they also generate color and flavor. To make malts with high enzyme activities, the maltster dries the barley gently, over about 24 hours, and brings the temperature slowly up to around 180ºF/80ºC. Such a malt is pale, and makes a light-colored, light-flavored brew. To make malts that have little enzyme activity but are rich in color and flavor, he kilns the barley at a high temperature, 300–360ºF/150–180ºC, to encourage browning reactions. Dark malts develop flavors that range from toasted to caramelized to sharp, astringent, and smoky. Brewers have many different kinds of malt to choose from — their names include pale or lager, ale, crystal, amber, brown, caramel, chocolate, and black — and often mix two or more malts in a single brew to obtain a particular combination of flavor, color, and enzyme power.

Once the malt has been kilned, the dried kernels can be stored for several months until they’re needed, when they’re ground into a coarse powder. They’re also made into malt extracts for both commercial and home brewers: the malted barley is soaked in hot water to remove its carbohydrates, enzymes, color, and flavor, and the liquid then concentrated to a syrup or a dry powder (p. 679).

Brewing Ingredients: Hops

Hops are the female flowers, or “cones,” of a Eurasian-American vine, Humulus lupulus, which bear small resin and aromatic oil glands near the base of their floral leaves, or bracts. They are an essential flavoring ingredient in beers. There are now several dozen brewing varieties, most of them European or European-American hybrids. Hops are picked off the plant when mature, dried, sometimes powdered and formed into pellets, and then stored until needed. They’re added to the brew liquid at the rate of about 0.5 to 5 grams per quart/liter, with the low figure typical of bland commercial brews, the high figure of flavorful microbrews and traditional Pilsners.

Four stages in the malting process. As the barley kernel germinates, it generates digestive enzymes, weakens cell walls, and begins the process of converting starch into fermentable sugars. The shading indicates the progress of cell-wall weakening and starch digestion. Malting is stopped when the growing shoot just reaches the tip of the kernel.

Bitterness and Aroma Hops provide two different elements: bitterness from phenolic “alpha acids” in their resins, and aroma from their essential oil. Some hop varieties contribute a dependable level of bitterness, while others are prized for their aroma. The important bittering compounds are the alpha acids humulone and lupulone. In their native form they’re not very soluble in water, but prolonged boiling transforms them into soluble structures that flavor the beer effectively. (Brewers sometimes use hop extracts that have been pretreated to produce the more soluble alpha acids.) Because boiling evaporates away many of the volatile aroma compounds, another dose of hops is sometimes added to the brew after the boiling, specifically to add aroma. The aroma of ordinary hops is characterized by the terpene myrcene, which is also found in bay leaf and verbena, and is woody and resinous. “Noble” hop varieties are dominated by humulene, which is more delicate, and often contain pine and citrus notes from other terpenes (pinene, limonene, citral). The American variety “Cascades” has a distinctive floweriness (due to linalool and geraniol).

Brewing Beer

The brewing of beer takes place in several stages.

• Mashing: ground barley malt is soaked in hot water. This revives the barley enzymes, which break starch into sugar chains and sugars, and protein into amino acids. The result is a sweet, brown liquid called the wort.
• Boiling: hops are added to the wort, and the two are boiled together. This treatment extracts the hop resins that flavor the beer, inactivates the enzymes, kills any microbes present, deepens the color of the wort, and concentrates it.
• Fermentation: yeasts are added to the cooled wort and allowed to consume sugars and produce alcohol until the desired levels of each are reached.
• Conditioning: the new beer is held for some time to purge it of off-flavors, clear it of yeasts and other materials that give it a cloudy appearance, and develop carbonation.

Here are some details of each stage.

The hop vine, Humulus lupulus, and its female flower structure, the cone, with a close-up of one of the cone’s clustered leaves, or bracts.

Mashing In the stage known as mashing, the coarsely ground malt is soaked in water at between 130 and 160ºF/54–70ºC for a couple of hours. Typical proportions are around eight parts water per one part malt. Mashing is completed by running the wort off the solid remains of the malt, which are then rinsed with hot water — “sparged” — to remove some remaining extractable materials before being discarded.

Mashing accomplishes several purposes. Above all, it gelates the starch granules and allows the barley’s enzymes to break down long starch molecules into shorter sugar chains and small fermentable sugars, and proteins into foam-stabilizing amino-acid chains and fermentable single amino acids. And it extracts all these substances, along with color and flavor substances, from the grain particles and into the water.

Because the different enzymes work fastest at different temperatures, the brewer can adjust the ratio of fermentable sugars to sugar chains, and amino acids to amino-acid chains, by varying the temperature and time of mashing. By this means he controls the beer’s final body, and the stability of its foam. Fully 85% of the carbohydrate in malt is starch. In the liquid wort, 70% or more is in the form of various sugars, mainly the two-glucose sugar called maltose. Most of the remaining carbohydrates, 5 to 25% of the dissolved solids, are the so-called dextrins, or sugar chains of from four glucose units to a few hundred, which get tangled up with each other, impede the movement of the water, and so provide a full-bodied consistency to the wort and beer. The dextrins and amino-acid chains will also slow the draining of fluid from the bubble walls of the beer foam, and so contribute to its stability in the glass.

Cereal Adjuncts Making the wort with nothing but barley malt and hot water is the standard method in Germany, and in many U.S. microbreweries. In most large breweries in the United States and elsewhere, unmalted “adjunct” sources of carbohydrate — ground or flaked rice, corn, wheat, barley, even sugar — are commonly added to the liquid to lower the amount of malt needed, and so the brewer’s production costs. Unlike malt, they contribute little or no flavor of their own. They’re therefore mostly limited to pale, mild brews like standard American lagers, which may start with almost as much adjunct grain as malt.

Water Water is the main ingredient in beer, so its quality has a definite influence on beer quality. Though modern brewers can tailor the mineral content of their water to the kind of beer they’re making, early brewers tailored their beers in part to make the best of the local waters. The sulfate-rich water of Burton-on-Trent gave English pale ales a bitterness that limited the use of hops, while the mild water of Pilsen encouraged Czech brewers to add large amounts of bitter and aromatic hops. The alkaline, carbonate-rich waters of Munich, southern England, and Dublin can balance the acidity of dark malts that normally extract too much astringent material from barley husks, and encouraged the development of dark German beers and British porters and stouts.

Boiling the Wort Once the liquid wort has been drawn off the grain solids, the brewer runs it into a large metal tank, adds hops, and boils it vigorously for up to 90 minutes. Boiling converts the insoluble hop alpha acids into their soluble form and develops the beer’s bitterness, and inactivates the barley enzymes and so fixes the carbohydrate mix — a certain portion of sugar for the yeasts to convert into alcohol, a certain portion of dextrins for the beer’s body. It sterilizes the wort so that the brewing yeasts won’t have any competition during fermentation, and it concentrates the wort by evaporating off some of its water. Boiling deepens the wort’s color by encouraging browning reactions, mainly between the sugar maltose and the amino acid proline. And it begins the process of clarifying the brew by coagulating large proteins and causing them to bind with tannins from the barley hulls, form large masses, and precipitate out of the solution. When boiling is finished, the wort is strained, then cooled and aerated.

OPPOSITE: Making beer. Beer is made in two basic ways. Ales are fermented in less than a week at a warm temperature and matured for days, while lagers are fermented for more than a week at a cold temperature and matured for weeks.

Fermentation With boiling, the brewer has finished transforming the bland barley grain into a rich, sweet liquid. Now the yeast cells transform this liquid into beer, which is far less sweet, but more complex in flavor.

There are two basic methods for fermenting beer, and they produce distinctive results. One is rapid fermentation at a high temperature with ale yeasts (strains of Saccharomyces cerevisiae) that clump together, trap the carbon dioxide gas that they produce, and rise to the wort surface. The other is slow fermentation at a low temperature with lager yeasts (Saccharomyces uvarum or carlsbergensis) that remain submerged in the wort and fall to the bottom when fermentation is over. These are often called “top” and “bottom” fermentations.

Top fermentation is usually carried out at between 64 and 77ºF/18–25ºC and takes two to seven days, during which the yeasty foam is skimmed off several times. Because the yeast layer at the top has a good supply of oxygen and is inevitably contaminated by other airborne microbes, including lactic-acid bacteria, top-fermented beers are often relatively acidic and strong in flavor. Bottom fermentation goes on at distinctly lower temperatures, 43 to 50ºF/6–10ºC, takes six to ten days, and produces a milder flavor. Bottom fermentation is the standard technique in the United States. Because warm temperatures encourage yeasts to generate particular aroma compounds (esters, volatile phenols), top fermentation produces fruity, spicy aromas; cold, slow fermentation produces crisp beers with a dry, bready flavor.

Conditioning The treatment of beer after fermentation varies according to the type of fermentation that has taken place: brief for fast top fermentation, prolonged for slow bottom fermentation.

Top-fermented beer is cleared of yeast and then run into a tank or cask for conditioning. The green beer, as it’s called fresh from fermentation, contains little carbon dioxide, has a sulfurous, harsh flavor, and is hazy with the detritus of dead yeast cells. In conditioning, a secondary fermentation is induced by adding to the green beer either a small amount of yeast and some sugar or fresh wort, or some actively fermenting wort (this is called Kräusening). Inside the closed cask or tank, the liquid traps and absorbs the carbon dioxide produced. Undesirable odors can be forced out of the beer by opening the container briefly and allowing some gas to escape. These traditional techniques are sometimes replaced by simply pumping pure carbon dioxide into the beer — carbonating it. Some hops or hop extract may also be added at this point to augment aroma, bitterness, or both. A few days of cooling and the use of a “fining” agent — isinglass (fish gelatin), clay, and vegetable gums are common — precipitate suspended proteins and tannins that might later form a haze when the beer is chilled for drinking; this is called “cold stabilization.” The beer is then centrifuged to remove any remaining yeast and precipitate, filtered, packaged, and usually pasteurized.

Lagering The conditioning process for bottom-fermented beer is somewhat different. The original Bavarian lager was packed in ice and allowed to rest in contact with its yeast dregs for several months. The yeast slowly produced carbon dioxide, which helped purge the beer of sulfury off-odors. Today, some traditional lagers are still aged for several months; but because storage has the economic disadvantage of tying up money and materials, the tendency is to lager the green beer at temperatures just above freezing for two to three weeks. Carbon dioxide may be pumped in to purge undesired aromas; and centrifuges, filters, and additives help clarify the beer. As a replacement for wooden casks, some beech or hazelwood chips may be thrown into the tank for flavor.

Additives More than 50 additives are permitted in American beer, including preservatives, foaming agents (usually vegetable gums), and enzymes — similar to meat tenderizers — that break down proteins into smaller molecules that are less likely to cloud the brew. Some companies avoid the use of preservatives, and usually advertise this fact on the label.

The Finished Beer In the end, brewing has transformed the dry, tasteless barley grain into a bubbly, bitter, acidic liquid (its pH is about 4) that is 90% water, 1 to 6% alcohol, and between 2 and 10% carbohydrates, mainly the long-chain dextrins that provide body.

Storing and Serving Beer

In contrast to wines, with their higher alcohol and antioxidant contents, most beers do not improve with age, and are at their best fresh from the brewery. Oxidation causes the gradual development of a stale, cardboard aroma (from nonenal, a fatty-acid fragment) and harshness on the tongue (from hop phenolic substances). Browning reactions cause other undesirable changes. Top-fermented ales develop a solvent-like note. Staling is slowed at low temperatures, so when possible beer should be stored in the cold. Britain does make “laying-down beers,” and Belgium bières de garde, which start out fermentation with a very high soluble carbohydrate content and continue to ferment slowly in the bottle, the continuous production of carbon dioxide and other substances helping to prevent oxidation and staling. They end with alcohol levels of 8% or more, and improve for a year or two.

Keep Beer in the Dark Beer should also be kept away from bright light, especially sunlight, and especially if it has been bottled in clear or green glass: otherwise it will develop a strong sulfurous odor. A cup of beer at a picnic can go skunky in a few minutes; bottled beer in a fluorescent-lit display case may deteriorate in a few days. It turns out that light in the blue-green to ultraviolet parts of the light spectrum reacts with one of the hop acids to form an unstable free radical, which in turn reacts with sulfur compounds to form a close relative of chemicals in the skunk’s defensive arsenal. Brown glass can absorb blue-green wavelengths before they get to the beer inside, but green bottles don’t. As a result, green-bottled German and Dutch beers are often sulfurous, and many consumers now expect this! One American brewer with trademark clear bottles developed a modified hop extract that’s free of the vulnerable hop acid, and this prevents its beer from going skunky.

Serving Beer In the United States, beer is often drunk ice-cold and straight from the can or bottle. This is fine for a light, thirst-quenching beer, but doesn’t do justice to beers designed to have some character. The colder any food is, the less full its flavor will seem. Lager beers are usually best served somewhat warmer than refrigerator temperature, around 50ºF/10 C, while top-fermented ales are served at a cool room temperature, from 50 to 60ºF/10–15ºC. Beers worth savoring are poured into a glass, where some of the carbon dioxide gas can escape and moderate their prickliness, and where their color and head of foam can be appreciated.

Beer Foam: The “Head” Beer is not the only intrinsically bubbly liquid we enjoy, but it’s the only one whose bubbles we expect to persist long enough to form a “head” of foam atop the glass. Beer lovers even value the ability of the foam to cling to the glass as the liquid level drops, a quality known as lacing (or, in more impressive German, Schaumhaftvermögen). There are many factors that influence foaming, from the amount of carbon dioxide dissolved in the beer to the way the beer is released from keg or can. Here are some of the most interesting.

Grain Proteins Stabilize the Head Foam stability depends on the presence in the bubble walls of emulsifier molecules with water-loving and water-avoiding ends (p. 802); the water-avoiding ends project into the gas while the water-loving ends stay in the liquid, and thus reinforce the gas-liquid interface. In beer, these molecules are mostly medium-sized proteins that come from the malt or from cereal adjuncts, whose proteins are more intact than malt’s and significantly improve head stability. Hop acids also contribute to foam stability, and become concentrated enough in the foam to make it noticeably more bitter than the liquid beneath. Cool-fermented lagers generally give more persistent foams than warm-fermented ales because the latter contain more foam-destabilizing higher alcohols from yeast metabolism (p. 762).

Nitrogen Makes Creamy Foams In the last decade, many beers have come to be endowed with an especially fine, creamy head that used to be largely limited to stouts. The creamy head comes from an artificial dose of nitrogen gas that may be injected into beer at the brewery, or in the bar or pub by the tap that delivers beer from the keg, or by a small device inside an individual beer can. Nitrogen is less soluble in water than carbon dioxide, so its bubbles are slower to lose gas to the surrounding liquid, and slower to coarsen and deflate. Nitrogen bubbles remain small, and persist. They also don’t carry the tart prickliness of carbon dioxide, which becomes carbonic acid when it dissolves in beer and on the surface of our tongue.

Foam in the Glass An initially vigorous pouring action develops the head of foam with a small, easily controlled portion of the beer. Once the foam is of the desired thickness, the rest of the beer can be poured in gently along the side of the glass, avoiding aeration and nucleation of new bubbles. The glass itself should be clean of any residues of oil or soap, which interfere with foaming. (These molecules have water-avoiding ends that pull the similar ends of the bubble-stabilizing proteins out of the bubbles.) By the same token, if a newly poured beer threatens to foam over, it can often be stopped in its tracks by touching the rim with a finger or lip, which carry traces of oil.

Kinds and Qualities of Beer

Beers are a wonderfully diverse group of drinks, and a good beer can be a mouth-filling experience, one that rewards slow savoring. There are several qualities worth appreciating:

• Color, which can range from pale yellow to impenetrable brown-black, and comes from the kinds of malt used
• Body, or weightiness in the mouth, which comes from the long remnants of starch molecules in the malt
• Astringency, from malt phenolic compounds
• Prickly freshness, from dissolved carbon dioxide
• Taste, which may include saltiness from the water, sweetness from unfermented malt sugars, acidity from roasted malt and from fermentation microbes, bitterness from hops and from dark-roasted malts, savoriness from malt amino acids
• Aroma, from woody, floral, citrusy hops; malty, caramel, and even smoky malt; and from the yeasts and other microbes, which can produce notes that seem fruity (apple, pear, banana, citrus), flowery (rose), buttery, spicy (clove), and even horsey or stable-like (p. 738)

Ales develop a characteristic tartness and fruitiness from their diverse group of fermentation microbes. Lagers have a more subdued aroma, part of whose foundation is cooked-corn-like DMS (dimethyl sulfide), which comes from a precursor in the lightly roasted malt and is produced while the wort is boiled and then cooled. But there’s tremendous variation in the flavors of these basic beers. Rich and somewhat sweet brews — porter, stout, barley wine — can even go well with desserts.

In addition to the many variations on the two themes of beer and ale, there are two kinds of beer that are worth special mention for their distinctiveness.

Wheat Beers German wheat beers differ from the usual Bavarian brew in four ways. First, a large fraction of the barley malt is replaced by wheat malt, which carries more protein, produces a more foamy and hazy brew, and lightens the typical malt flavor. Second, wheat beers are top-fermented like ales, and so develop more tartness and fruitiness. Third, the culture often includes an unusual yeast (Torulaspora) that produces aroma compounds not usually found in beer. These volatile phenols (vinyl guaiacol, p. 738) may suggest cloves and similar spices, but also a medicinal quality like that of plastic bandages, or an animal quality reminiscent of the barnyard or stable. Finally, some wheat beers are not fully clarified, and retain some of their yeast, which gives them a cloudy appearance and yeasty flavor. German wheat beers may be called Weizen for “wheat,” Hefe-weizen for “yeast-wheat,” or Weissen for “white,” referring to their cloudy appearance.

Some American breweries now produce wheat beers on the German model, but usually without the phenol-producing yeast; they are mild, tart, and cloudy.

Belgian Lambic Beers The brewers of Belgium have been more inventive than any others. They allow many different microbes to participate in the fermentation; they ferment some beers for years, either continuously or by restarting them; they flavor their beers with spices and herbs, and even re-ferment them with fresh fruits to make a hybrid beer and fruit wine. They generally used aged hops, which are less harmful to the unusual brewing microbes, less bitter, and higher in drying, slightly astringent, wine-like tannins.

The most unusual Belgian beers are the lambics. The hallmark of brewing traditional lambic is a spontaneous and months-long fermentation of the wort in wood barrels. Once the wort has been boiled, it is cooled in a broad open tank, where it picks up microbes from the ambient air. The cool wort is then poured into wooden casks that contribute microbes from previous batches, and ferments in the casks for 6 to 24 months. The fermentation proceeds in four stages: an initial growth of wild yeasts (Kloeckera and others) and various bacteria (Enterobacter and others) that takes 10–15 days and produces acetic acid and vegetable aromas; the main alcohol-producing growth of Saccharomyces yeasts, which dominate for several months; at 6 to 8 months, the acid-producing growth of lactic and acetic bacteria (Pediococcus, Acetobacter); and finally the growth of Brettanomyces yeasts, which produce a range of fruity, spicy, smoky, and animal aromas (see box, p. 730). The resulting brew may then be blended with other lambics and aged to make gueuze, with a wine-like acidity and complexity; or blended with some ordinary top-fermented ale and flavored with sugar and coriander to make faro; or re-fermented in the barrel for four to six months with fresh whole cherries or raspberries, to make kriek and framboise.

Asian Rice Alcohols: Chinese Chiu and Japanese Sake

Sweet Moldy Grains

The peoples of eastern Asia developed their own distinctive form of alcohol, one that the rest of the world is coming to appreciate more and more. It’s not exactly a wine, because it’s fermented from starchy grains, mainly rice. But it’s not exactly a beer either, because the grain starch is not digested into fermentable sugars by grain enzymes. Instead, Asian brewers use a mold to supply the starch-digesting enzymes, and the mold digests the grain starch at the same time that the yeasts are converting the sugars into alcohol. The resulting liquid can reach an alcohol concentration of 20%, far stronger than Western beers and wines. Chinese chiu and Japanese sake don’t have the grapey fruitiness or acidity of wine, nor the malt or hop characters of beer. Because it’s made from only the starchy heart of the rice grain, sake is perhaps the purest expression of the flavor of fermentation itself, surprisingly fruity and flowery even though no fruit or flower has come near it.

Why and how did Asians come up with this alternative to sprouting grains? The historian H. T. Huang suggests that the key was their reliance on small, fragile millet and rice grains, which unlike barley and wheat are easily and usually cooked whole. Huang speculates that leftover cooked grains were frequently left sitting out long enough to get moldy; and because there are air spaces in a mass of grains, the oxygen-requiring molds would have grown well and digested starch throughout the mass. People eventually noticed that moldy rice tasted sweet and smelled alcoholic. Sometime before the 3rd century BCE, these simple observations led to a regular technique for producing alcoholic liquids. By 500 CE, a Chinese source lists nine different mold preparations and 37 different alcoholic products.

Today, few people outside of China have heard of chiu, but many millions have heard of its Japanese counterpart, sake(pronounced “sa-kay”). Rice cultivation and probably chiu production were brought to Japan from the Asian mainland around 300 BCE. Over the following centuries, Japanese brewers so refined chiu that it became something distinctive.

Starch-Digesting Molds

Though modern industrial production has brought a number of common shortcuts and simplifications, Chinese and Japanese brewers have traditionally used very different preparations for breaking rice starch down into fermentable sugars.

Chinese Chhü : Several Molds and Yeasts The ancient Chinese preparation, chhü, is usually made from wheat or rice, and includes several different kinds of mold as well as the yeasts that will eventually produce the alcohol. Some of the wheat may be roasted or left raw, but most is steamed, coarsely ground, shaped into cakes, and then left to mold in incubation rooms for several weeks. Species of Aspergillus grow on the outside, and species of Rhizopus and Mucor on the inside. Aspergillus is the same kind of mold used to digest soybeans to make soy sauce and Rhizopus is the major mold in soybean tempeh (p. 496, 500), while Mucor is important in some kinds of aged cheeses. All of them accumulate starch-and protein-digesting enzymes, and generate trace byproducts that contribute flavor. Once the grain cakes have been well permeated with microbes, they’re dried for storage. When needed for chiu production, they’re soaked in water for several days to reactivate the microbes and their enzymes.

Japanese Koji and Moto: One Mold, Separate Yeast The Japanese koji, by contrast, is made fresh for each particular sake brewing, is based only on polished, unground rice, and is inoculated with a selected culture of Aspergillus oryzae alone, with no other molds. The mold preparation for sake therefore doesn’t provide the complexity of flavor that the Chinese preparation does, with its roasted wheat, variety of microbes, and period of drying.

Because the koji contains no yeasts, the Japanese system requires a separate source of yeast. The traditional yeast preparation, the moto, is made by allowing a mixture of koji and cooked rice gruel to sour spontaneously with a mixed population of bacteria, mainly lactic acid producers (Lactobacillus sake, Leuconostoc mesenteroides, and others) that contribute tart and savory tastes and some aroma. A pure yeast culture is then added and allowed to multiply. Because this microbe-soured moto takes more than a month to mature, it has been largely replaced by the simple addition of organic acids to the moto mash, or by the addition of acids and concentrated yeasts directly to the main fermentation. These time-saving methods tend to produce lighter, less complex sakes.

Brewing Rice Alcohols

Simultaneous, Stepwise Fermentation Chinese and Japanese brewing methods differ in important details, but they also share several important features. The starch-digesting molds and alcohol-producing yeasts are added to the cooked rice gruel together, and work simultaneously. Unlike the making of beer, where a liquid is extracted from the grain and only the liquid is fermented, the thick gruel of cooked rice is fermented whole. And the rice is introduced gradually into the fermentation, not all at once: new portions of cooked rice and water are added to the vat at intervals during the fermentation, which lasts from two weeks to several months. All of these practices apparently contribute to the yeasts’ ability to continue producing alcohol to high concentrations. When rice is added toward the end of fermentation, some sugar remains unmetabolized by the yeasts, and the resulting alcohol is sweet.

Chinese Practice: Ordinary Rice and High Temperatures Traditional Chinese brewing begins with soaking the mold preparation in water for several days, and then proceeds with the periodic addition of ordinary cooked rice over the course of an initial fermentation that may last one or two weeks at a temperature around 85ºF/30ºC. At the end of this phase, the mash is often divided into smaller containers and held at cooler temperatures for weeks or months. The liquid is then pressed from the solids, filtered, adjusted with water and colored with caramel, pasteurized at 190–200ºF/85–90ºC for 5–10 minutes, matured for several months, then filtered and packaged. The high-temperature pasteurization helps develop the finished flavor.

Japanese Practice: Polished Rice and Low Temperatures Chinese brewers use rice that has been milled to remove about 10% of the grain, only slightly more than is removed to make ordinary white rice for cooking (p. 472). In Japan, however, the rice for anything above the standard grade of sake must be milled to remove a minimum of 30% of the grain, and the highest grades of sake are made with rice that has been polished down to 50% or less of its original weight. The center of the rice grain is the portion that contains the most starch and the least protein or oil, so the more the outer layers of the rice are ground away, the simpler and purer the remaining grain, and the less grain flavor it contributes to the final liquid.

Sake is also fermented at significantly lower temperatures than Chinese rice alcohols. Beginning in the 18th century, most sake brewing was reserved for the winter months, and this remains largely the case today. The upper limit for sake brewing is around 64ºF/18ºC, and brewers of the highest grades will keep the temperature at a distinctly chilly 50ºF/10ºC. In these conditions, the fermentation takes about a month instead of two to three weeks, and the mash accumulates two to five times the normal quantity of aroma compounds, notably the esters that provide apple, banana, and other fruity notes.

Once the sake fermentation is complete, the liquid is pressed from the solids, then filtered, diluted with water to 15–16% alcohol, and held for some weeks to allow the flavor to mellow. It’s also pasteurized (at 140–150ºF/60–65ºC) after filtering and again before bottling to denature any remaining enzymes, one of which otherwise slowly generates a particularly unpleasant volatile (sweaty isovaleraldehyde).

Varieties of Sake There is a broad range of different grades and kinds of sake. Both the cheapest and the standard grades are made by adding substantial amounts of pure alcohol to the mash just before pressing. This became standard industrial practice during the war years because it greatly increases the yield from a given quantity of rice. Sugar and various organic acids can also be added to these grades. At the other end of the scale, there are premium versions made with nothing but rice, water, and microbes, painstakingly cultured in the traditional way. The box below gives examples of some kinds worth seeking out.

Though much sake is drunk warm as Chinese rice alcohols are, connoisseurs prefer to chill finer examples. In general, sake is less tart and more delicately flavored than wine. Savory amino acids are an important element. Its aroma varies a great deal depending on how it was made, and features the biochemical artistry of the yeasts. Fruity esters and flowery complex alcohols are usually prominent.

OPPOSITE: Making sake. One of the unusual features of sake fermentation is the repeated addition of cooked rice to the fermenting mash over the course of several weeks.

Sake Is Fragile Sake and its delicate flavors are vulnerable to alteration by exposure to both light and high temperatures. It’s best drunk as young as possible. The clear and blue bottles in which it’s usually packaged offer little protection, so sake should be kept in the cool and dark of the refrigerator, and once opened should be consumed quickly.

Distilled Spirits

Distilled spirits are the concentrated essence of wine and beer. They’re the product of a basic chemical fact: different substances boil at different temperatures. The boiling point of alcohol is about 173ºF/78ºC, well below water’s 212ºF/100ºC. This means that if a mixture of water and alcohol is heated, more of the alcohol than the water will end up in the vapor. That vapor can then be cooled and condensed back into a liquid that has a higher alcoholic content than the original beer or wine.

Distilled spirits were first valued, and still are, for their high alcohol content. But there’s much more to them than their intoxicating power. Like alcohol, the substances that give wine and beer their aroma are also volatile: so the same process that concentrates alcohol also concentrates aroma. Distilled alcohols are some of the most intensely flavorful foods we have.

The History of Distilled Spirits

The Discovery of Distillation High concentrations of alcohol are toxic to all living things, including the yeasts that produce it. Brewing yeasts can’t tolerate more than about 20%. So stronger drink can only be made by physically concentrating the alcohol in fermented liquids. The key to discovering distilled alcohol would have been two observations: that the vapors of a heated liquid can be recaptured by condensing them on a cool surface, and that the vapors of heated wine or beer are more strongly alcoholic than the original liquid.

The practice of distillation itself appears to be very old. There’s evidence that the Mesopotamians were concentrating the essential oils of aromatic plants more than 5,000 years ago, using a simple heated pot and a lid onto which vapors condensed and could be collected. And Aristotle noted in the 4th century BCE in his Meteorology that “Sea water, when it is converted into vapor, becomes drinkable, nor does it form sea water when it condenses again.” Concentrated alcohol may have been discovered for the first time in ancient China. Archaeological finds and written documents suggest that Chinese alchemists were distilling small amounts of concentrated alcohol from grain preparations around 2,000 years ago. A privileged few were drinking it before the 10th century, and by the 13th it was a commercial product.

Spirits and Waters of Life In Europe, significant quantities of distilled alcohol were produced around 1100 at the medical school in Salerno, Italy, where it developed its reputation as a uniquely valuable medicine. Two hundred years later, the Catalan scholar Arnaud of Villanova dubbed the active principle of wine aqua vitae, the “water of life,” a term that lives on in Scandinavia (aquavit), in France (eau de vie), and in English: whisky is the anglicized version of the Gaelic for “water of life,” uisge beatha or usquebaugh, which is what Irish and Scots monks called their distilled barley beer. Throughout the Old World, alchemists thought of distilled alcohol as a uniquely powerful substance, the quintessence or fifth element that was as fundamental as earth, water, air, and fire. The first printed book devoted to distillation, Hieronymus Brunschwygk’s Liber de arte distillandi (1500), explained that the process achieves

It’s this connection between distillation and the pure and ethereal that gives us our synonym for distilled alcohol, spirits.

From Medicine to Pleasure and Drug of Oblivion For several centuries after its discovery, aqua vitae was produced in apothecaries and monasteries and prescribed as a cordial, a medicine to stimulate the circulation (the word comes from the Latin for “heart”). It seems to have been liberated from the pharmacy and drunk for pleasure in the 15th century, when the terms Bernewyn and brannten Wein, ancestors of our word brandy that meant “burning” or “burnt” wine, appear in German laws about public drunkenness. This is also when winemakers in the Armagnac region of southwest France began to distill their wine into spoilage-resistant brandy for shipping to northern Europe. Gin, a whisky-like medicinal concoction from rye, with juniper added for its flavor and diuretic effect, was first formulated in 16th century Holland. The renowned brandy of France’s Cognac, just to the north of Bordeaux, arose around 1620. Rum was first made from molasses in the English West Indies around 1630, and monastic liqueurs like Benedictine and Chartreuse date from about 1650 on.

Over the next couple of centuries, the drinkability of spirits improved as distillers learned how to refine their composition. First came double distillation, in which a wine or beer is distilled, and the distillate then distilled a second time; then in the late 18th and early 19th centuries came ingenious French and English column stills, which produce alcohols of greater purity in one continuous process. The growing availability and drinkability of distilled liquors meant that addiction became a serious problem, particularly among the urban populations of the Industrial Revolution. In England the principal scourge was cheap gin, which the average Londoner in the late 18th century consumed at the rate of nearly a pint/400 ml a day “to seek relief in the temporary oblivion of his own misery,” as Charles Dickens later wrote in Sketches by Boz. Government control of production and social progress later moderated the problem of alcohol addiction, but hasn’t eliminated it.

Whiskey in America Distilled alcohol was so popular in North America that it gave us an enduring legacy: the Internal Revenue Service! In the early days of the colonies and then the United States, molasses was more plentiful than barley, and rum more common than beer. Rye and barley spirits were also being distilled in the northern colonies by 1700, and Kentuckycorn whiskey by 1780. After the Revolutionary War, the new American government tried to raise revenues for its war debts by taxing distillation, and in 1794 the largely Scots-Irish region of western Pennsylvania rose in the short-lived Whiskey Rebellion. When President Washington called out federal troops to put it down, the rebellion went underground and “moon-shining” became entrenched, especially in the poor hills of the South where the small amount of corn that could be grown would fetch a better price if fermented and distilled. This evasion led the federal government to form the Office of Internal Revenue in 1862. Sixty years later, the national taste for hard liquor was an important stimulus to the temperance movement that culminated in Prohibition.

Recent Times: The Rise of the Cocktail It was in the 19th century that mixtures of distilled and other alcohols, or cocktails, became fashionable before-dinner drinks in Europe and the Americas. This development led to a mind-numbing explosion of inventiveness: bartenders’ manuals now list hundreds of different named cocktails. The origins of the preeminent cocktail, the martini (gin and vermouth), are disputed; it may have been invented several times in different places. The gin and tonic comes from British India, where gin helped make antimalarial quinine water more palatable. In the United States, one of the first famous mixed drinks was the sazerac of New Orleans (brandy and bitters), while Winston Churchill’s mother is said to have incited the creation of the manhattan (whiskey, vermouth, bitters) at a New York club. Prohibition and harsh “bathtub gin” slowed further progress from 1920 to 1934. In the 1950s, mixologists discovered the value of vodka as a largely flavorless alcohol, and the appeal of sweet-tart fruit juices and sweet liqueurs. Over the next few decades they concocted such broadly popular drinks as the mai tai, piña colada, screwdriver, daiquiri, margarita, and tequila sunrise. In the 1970s, vodka dethroned whiskey as America’s best-selling spirit.

The late 20th century brought a modest revival of interest in the more austere classic cocktails, and in fine distilled spirits of all kinds, mixed with nothing more than water.

Making Distilled Alcohols

All distilled alcohols are made in basically the same way.

• Fruits, grains, or other sources of carbohydrates are fermented with yeasts to make a liquid with a moderate alcohol content, from 5 to 12% by volume.
• This liquid is heated in a chamber that collects the alcohol-and aroma-rich vapors as they escape from the boiling liquid, and then passes them across cooler metal surfaces, where the vapors condense and are collected as a separate liquid.
• The concentrated alcoholic liquid is then modified in various ways for consumption. It may be flavored with herbs or spices, or aged in wood barrels. The alcohol content is usually adjusted with the addition of water before it’s bottled for sale.

The Distilling Process The essential principle of distillation is a simple one: both alcohol and aromatic substances are more volatile in water than water itself, so they evaporate in disproportionate amounts from wine and beer and become concentrated in the vapor. But it’s not a simple matter to make a delicious distilled alcohol, or even a drinkable one. Yeast fermentation produces thousands of volatile substances, and not all of them are desirable. Some are unpleasant, and others, notably methanol, are dangerously toxic.

Selecting Desirable Volatiles Distillers must therefore control the composition of the distilled liquid. They do this by subdividing the vapor into fractions that are more and less volatile, and collecting mainly the fraction that is richest in alcohol. The fraction more volatile than alcohol, often called the “heads” or “foreshots” because it evaporates earlier than alcohol, includes toxic methanol, or wood alcohol, and acetone. The fraction that’s less volatile than alcohol, the “tails” or “feints,” includes a host of aromatic substances that are desirable. Among these “congeners” (substances that accompany alcohol) are esters, terpenes, and volatile phenolics, along with some substances that are desirable in limited amounts. The most notable of the latter are the “higher” alcohols, whose long, fat-like chains can give spirits a full, almost oily body, but also contribute a pronounced harsh flavor and unpleasant aftereffects. They’re often called fusel oils. (Fusel is the German for “rotgut.”) A small dose of fusel oils gives a distilled alcohol character; too much makes it unpleasant.

Purity and Flavor The best indication of how strongly flavored a distilled alcohol will be is the percentage of alcohol in the liquid immediately after distillation, before it’s further treated by aging and/or dilution with water to its final strength (see box, p. 765). The higher the alcohol content to which it’s distilled, the purer a mixture of alcohol and water it is, the lower the proportion of fusel oils and other aromatics, and so the more neutral the flavor. Vodkas are usually distilled to 90% alcohol or more; brandies and flavorful malt and corn whiskies to 60–80%. Crudely distilled moonshine is only 20–30% alcohol, and therefore harsh and even hazardous.

Pot or Batch Distillation: Selecting Volatiles by Time There are two ways for distillers to separate the vapor into undesirable heads, somewhat desirable tails, and the desirable main run of alcohol. The original way, and the way that is still used for many of the finest liquors, is separation in a simple pot still by time. It can take 12 hours or more for a batch of beer or wine to be heated close to the boil and then distilled. The very volatile head vapors come off first, followed by the main alcohol-rich run, and then the less volatile fusel-oil tails. So the distiller can divert the initial vapors, collect the desirable main run in a different container, and then divert the late vapors again. In practice, distillers repeat the pot distillation, the first pass giving spirits with 20–30% alcohol, and the second 50–70%.

The structures of several different alcohols. Methanol is a poison because our bodies convert it into formic acid, which accumulates and damages the eyes and brain. Ethanol is the main alcohol produced by yeasts. Butyl and amyl alcohols are two of the “higher,” or longer-chain alcohols. When concentrated by distillation, they contribute an oily consistency to spirits thanks to their fat-like hydrocarbon tails.

Continuous Distillation: Selecting Volatiles by Position The second way in which distillers can separate the desirable volatiles from the rest is by their position in a column still, an elongated chamber developed by French and British distillers during the Industrial Revolution. In a column still, the starting wine or beer is fed into the column from the top, and the column is heated from the bottom with steam. The bottom of the column is therefore the hottest region, the top the coolest. Methanol and other low-boiling substances remain vaporized throughout all but the very top of the column, while fusel oils and other aromatics with high boiling points will condense on collection plates at hotter positions toward the bottom of the column, and alcohol will condense — and can be collected — at an intermediate point. The advantage of the column still is that it can be operated continuously and without the necessity of close monitoring; the disadvantage is that it offers less opportunity than the pot still for the distiller to control the composition of the distillate. When two or more columns are run together in series, they’re capable of producing a neutral distillate that is 90–95% alcohol.

Pot distillation. As wine or beer is gradually heated, the composition of its vapors changes, with very volatile substances evaporating first, less volatile substances later. The distiller diverts early and late vapors with their undesirable volatiles, and collects the “main run,” rich in alcohol and desirable aromas.

Continuous distillation in a column still. The plates in each column are hottest at the steam input and coolest at the other end. Substances with low boiling points, including alcohol, are concentrated in the vapor that leaves the first column and rises in the second, and the alcohol-rich fraction is collected at a particular position in the second column.

Maturation and Aging Fresh from the still, distilled liquors are as colorless as water, or “white.” They’re also rough and harsh, so all are matured for weeks or months to allow the various components to react with each other, form new combinations, and become less irritating. From this point, the spirits are handled differently according to the kind of product they’re meant to become. “White” spirits, including vodka and eaux de vie made from fruits, are not aged; they may be flavored, then adjusted to the proper alcohol content by the addition of water, and bottled. “Brown” spirits, including brandies and whiskies, are so called because they’re aged in wood barrels, from which they derive a characteristic tawny color and complexity of flavor. (Some brown spirits may be colored with caramel instead.) Spirits may be barrel-aged for anything from a few months to decades, during which their flavor changes considerably.

The extraction, absorption, and oxidation processes that take place during barrel aging result in the development of a mellow, rich flavor (p. 720). And the barrel allows both water and alcohol to evaporate from the spirits, thus concentrating the remaining substances. A barrel may lose several percent of its volume per year; that portion is called “the angels’ share,” and it may approach half the barrel volume after 15 years.

Final Adjustments When spirits are judged ready for bottling, they’re usually blended to obtain a consistent flavor, and diluted with water to the desired final alcohol content, in the neighborhood of 40%. Small quantities of other ingredients may be added to fine-tune the flavor and color; these include caramel coloring, sugar, a water extract made by boiling wood chips (the boisé of Cognac and Armagnac), and wine or sherry (blended U.S. and Canadian whiskeys).

Chill-Filtering Many spirits are chill-filtered: chilled to below the freezing point of water, and then filtered to remove the cloudy material that forms. The substances that form the cloud are poorly soluble fusel oils and volatile fatty acids from the original spirits, and a variety of similar substances extracted from the barrel. Their removal prevents the spirits from clouding when the drinker chills them or dilutes them with water, but it also removes some flavor and body, so some producers choose not to chill-filter. Clouding does not occur in spirits with more than about 46% alcohol, so such undiluted “cask-strength” spirits are often not chill-filtered. (Some spirits cloud spectacularly; see p. 771).

Serving and Enjoying Spirits

Crystal Decanters Can Be Hazardous High-alcohol spirits are biologically and chemically stable and can be kept for years without spoiling. One traditional and decorative way of storing them has been the decanter made of glass crystal, which derives its weight and appearance from the element lead. Unfortunately, lead is powerfully toxic to the nervous system, and readily leaches from crystal into spirits and other acidic liquids. Old decanters that have been used many times have been preextracted and are safe to use; new ones should either be pretreated to remove lead from the inner surfaces, or only used for serving, not storing.

The Flavors of Spirits Spirits are served at temperatures ranging from ice cold (Swedish aquavit) to steaming hot (Calvados). To appreciate nuances of flavor, they’re best served at room temperature, and if necessary warmed in the hands. Their aroma is intense, so much so that it can be just as enjoyable to sniff as to sip; Scotch lovers call this nosing. At distilled strengths, alcohol has an irritating and then numbing effect on the nose that is accentuated at high temperatures. To reduce the interference of alcohol and bring out more delicate aromas, connoisseurs often dilute whiskies with good-quality water to 30% or 20% alcohol. Different kinds of spirits have very different flavors, which derive from the original ingredient — grape or grain — from the yeasts and fermentation, from the prolonged heat of distillation, and from contact with wood and the passage of time. Spirits with a high fusel oil content have an unctuous quality in the mouth, while more neutral spirits give a cleansing, drying effect. The aromas of spirits often persist in the mouth long after the liquid itself has been swallowed.

Kinds of Spirits

Distilled spirits are made all over the world from all kinds of alcoholic liquids. Here are brief descriptions of the more prominent.

Brandies Brandies are spirits distilled from grape wine. The two classic brandies are Cognac and Armagnac, the first named for a town and the second for a region in southwestern France, each not far from Bordeaux. Both are made from neutral white grapes (mainly Ugni blanc) that are casually fermented into wine, and the wines distilled between harvest and mid-spring (the best brandies are distilled first; as the wine sits, it loses esters and develops volatile acidity and off-aromas). Cognac is double-distilled from the wine with its yeast lees to an alcohol content of about 70%, most Armagnac single-distilled without yeast in a traditional column still to about 55%. Each is then aged in new French oak barrels for a minimum of six months; some Cognacs are aged for 60 years or more. Before bottling, each is diluted to about 40% alcohol and may be adjusted with sugar, oak extract, and caramel. Cognac has a fruity, flowery character thanks to the distillation of esters from the wine yeasts. Armagnac is relatively rough and complex thanks to its higher content of volatile acids; it’s said to have a prune-like aroma. With long aging, both develop a prized rancio (“rancid”) character from the transformation of fatty acids into methyl ketones, which also provide the distinctive aroma of blue cheese(p. 62).

Less renowned brandies are made elsewhere in France and throughout the world in a variety of ways, from the industrial to the artisanal. Especially interesting are brandies distilled from more distinctive grape varieties than the purposely neutral Ugni blanc.

Eaux de vie, Fruit Alcohols, White Alcohols These are various terms that are less confusing than their synonym “fruit brandy”: they name spirits that are distilled from fermented fresh fruits other than grapes. Unlike true “burned wines,” which offer a complicated, transformed wineyness, eaux de vie capture and concentrate the distinctive essence of the fruits from which they’re made, so they can be savored almost pure rather than in their flesh. France, Germany, Italy, and Switzerland are especially noted for their fine fruit alcohols. Some popular examples are apple (Calvados), pear (Poire Williams), cherry (Kirsch), plum (Slivovitz, Mirabelle, Quetsch), and raspberry (Framboise); less widely known are apricot (French Abricot), figs (North African and Middle Eastern Boukha), and watermelon (Russian Kislav).

A single bottle of eau de vie may represent from 10 to 30 lb/4.5–13.5 kg of the fruit. Fruit alcohols are generally double-distilled to about 70% alcohol and are not aged in barrels — hence their lack of color — because their point is to concentrate the fruit’s own flavor into an intense, full, but pure essence. One prominent exception to this rule is Calvados, an apple eau de vie that is distilled in Brittany from a blend of varieties, some too sour or bitter for eating. The apples are slowly fermented into cider over the course of several cool weeks in the autumn, and the cider is then distilled in either pot or column stills, depending on the district. The distillate is then matured in old barrels for a minimum of two years. Slivovitz, a Balkan plum alcohol, is also barrel-aged.

Whiskies and Whiskeys Whiskies (United Kingdom) and whiskeys (elsewhere) are spirits that have been distilled from fermented grains, mainly barley, maize, rye, and wheat, and then aged in barrels. The term comes from a barley distillate of medieval Britain, but is now applied to largely maize distillates in the United States and Canada, and mixed grain distillates in many countries.

Scotch and Irish Whiskies There are three kinds of Scotch whisky. One, malt whisky, is made in the Highlands and islands entirely from malted barley. It’s distilled twice in pot stills to about 70% alcohol, and has a strong, distinctive flavor. Another, grain whisky, is less flavorful and less costly; it is made in the lowlands from various cereals and just a small portion (10–15%) of malted barley to convert their starches into sugars, and distilled in a continuous still to a neutral 95% alcohol. The third and most common is a blend of malt and grain whiskies, with grain whisky accounting for 40–70%. Such blending began in the 1860s for economic reasons, and turned out to produce a milder, more widely appealing drink just in time to replace brandy when the insect scourge phylloxera devastated European vineyards in the 1870s and 1880s. This is when Scotch developed its international reputation. Today, Scotch connoisseurs prize the distinctive “single-malt” whiskies produced by the few remaining small distillers of all-malt whisky.

Whisky makers produce beer, omitting the hops, and then distill it, yeasts and all. The distillate is aged in used oak barrels for a minimum of three years, then diluted with water to around 40% alcohol, and is usually chill-filtered. Scotch whisky owes its special flavor largely to the barley malt. Malt whiskies from Scotland’s west coast have a unique, smoky flavor that comes from the use of peat fire for drying the malt, and peaty water for mashing the grain before fermentation. Peat, the mat of decaying and decayed vegetation that once was the cheapest fuel available in swampy areas of Britain, contributes volatile organic molecules to the brew that find their way into the distillate.

Most Irish whisky is made from a mixture of about 40% malted and 60% unmalted barley. For this reason, and because it is pot-distilled twice and then again in a column still, Irish whisky is milder than malt Scotch and even some Scotch blends.

American and Canadian Whiskeys North American whiskeys are produced mainly from the New World’s indigenous grain, maize. The most prominent corn whiskey is bourbon, which is named for a county in Kentucky where maize grew well in colonial times, and where there was abundant water for both mashing the grains and cooling the distillate.

Bourbon is made from a mash that’s usually 70–80% maize, 10–15% malted barley to digest the starch, and the remainder rye or wheat. After fermenting for two to four days, the whole mash, grain residues and yeast included, is distilled in a column and then a kind of continuous pot still to 60–80% alcohol. The distillate is aged for at least two years in new, charred American oak barrels, which give bourbon a deeper color and stronger vanilla note than Scotch whiskies have. Summer temperatures that can reach 125ºF/53ºC in the warehouses modify and accelerate the chemical reactions of aging. Bourbons are generally chill-filtered; in fact this technique was invented by the Tennessee whiskey maker George Dickel around 1870. Unlike French brandies and Canadian whiskeys, bourbon cannot be colored, sweetened, or flavored; the only additive allowed is water.

Canadian whiskeys are among the mildest and most delicate of the spirits made from grains. They are a blend of a light-flavored column-distilled grain whiskey with small amounts of stronger whiskeys; they can also include wines, rum, and brandy, up to 9% of the blend. They’re aged for a minimum of three years in used oak casks.

Gins There are two principal styles of distilled gin made today, English and Dutch, as well as cheaper gin that cannot be called distilled because its flavorings are simply added to neutral alcohol.

The traditional Dutch production method is to distill a fermented mixture of malt, corn, and rye two or three times in pot stills at low proof: that is, the distillate contains a fair amount of congeners, and resembles a light whisky. Then this distillate is distilled one last time, to a minimum of 37.5% alcohol, along with juniper berries and other spices and herbs, whose aromatic molecules end up in the final gin.

English-style, or “dry” gin, begins with neutral 96% alcohol produced from grain or molasses by other distilleries. This flavorless liquid is then diluted with water and redistilled in a pot with juniper and other flavorings. Juniper is required for the product to be called gin, and most gins also contain coriander. The other ingredients may include citrus peel and a great variety of spices. This distillate is diluted before bottling to 37.5 to 47% alcohol.

The primary aromas in gin come from the terpene aromatics (p. 390) in the spices and herbs, especially notes of pine, citrus, flowers, and wood (pinene, limonene, linalool, myrcene). Dutch gin is generally enjoyed on its own, while beginning in the 1890s, English dry gin inspired many cocktails and tall mixed drinks, including the martini, gimlet, and gin and tonic.

Rums Rum got its start in the early 17th century as a by-product of sugar making in the West Indies. Yeasts and other microbes readily grew in the leftover molasses and wash waters, the yeasts producing alcohol and the bacteria all kinds of aromatic substances, many of them not pleasant. From this mixed material, primitive distillation equipment and methods produced a strong, harsh liquid that was given mainly to slaves and sailors, and traded to Africa for more slaves. Controlled fermentations and improvements in distilling technology brought more drinkable rums in the 18th and 19th centuries.

There are now two distinct styles of rum. The modern light style is made by fermenting a molasses solution with a pure yeast culture for 12–20 hours, then distilling it to about 95% alcohol in a continuous still, aging it for a few months to eliminate roughness in the flavor, and diluting and bottling it at around 43% alcohol. Some light rums are given a brief time in barrels, but then are passed over charcoal to remove the color and some of the flavor.

Traditional Rums Traditional rums are made very differently, and have a much stronger flavor and darker color. Most come from Jamaica and the French-speaking Caribbean (Martinique, Guadeloupe). They were once fermented for up to two weeks with a spontaneous group of microbes, and often by adding the already strong-flavored lees of one fermentation to the next vat. Today, most traditional rums are fermented for a day or two with mixed microbial cultures dominated by an unusual yeast (Schizosaccharomyces) that excels in ester production. They’re then pot-distilled to a much lower alcohol content, and therefore end up with four to five times the quantity of aroma compounds that light rum has. Finally they’re aged in used American whiskey casks, where they get most of their color. Caramel can be added to deepen the color and flavor, a procedure that seems appropriate since rum is made from sugar in the first place.

Rums as Ingredients Rums are delicious on their own, but it’s their aptitude for other foods that accounts for much of their popularity. Light rums go well with tart-sweet fruits and are the base for a number of tropical cocktails, including piña coladas and daiquiris. Medium and dark rums are a useful ingredient in sweets of all kinds thanks to their full caramel flavor.

Vodkas Vodka was first distilled in Russia in medieval times and for medical purposes, and became a popular drink in the 16th century. Its name means “little water.” It has traditionally been made from the cheapest source of starch available, usually grain, but sometimes potatoes and sugarbeets. The source is unimportant, since the fermented base is distilled to eliminate most aromatics, and the remainder is removed by filtration through powdered charcoal to produce a smooth, neutral flavor. The essentially pure mixture of alcohol and water is then diluted with water to the desired strength, a minimum of around 38%, and bottled without aging.

Vodka was scarcely known in the United States until the 1950s, when it was discovered as an ideal alcohol for blending with fruit and other flavors in cocktails and tall mixed drinks. Recent years have brought vodkas flavored with citrus and other fruits, with chillis, and with barrel aging.

Grappa, Marc These are the Italian and French names for spirits distilled from pomace, the residue of grape skins and pulp, seeds and stems left behind when wine grapes are pressed. These drinks were born from frugality, as a way of getting the most out of the grapes. The solid remains still have juice, sugar, and flavor in them, so with some water and another period of fermentation, they generate alcohol and flavors that can then be concentrated by distillation, leaving behind the harsh astringency and bitterness. Pomace distillates were very much a by-product, usually distilled just once and often without diverting the heads and tails, and were bottled as is: so they were strong and harsh, something to warm and stimulate the vineyard workers, but not something to savor. In the last few decades, producers have been distilling more selectively and sometimes aging the results to make a fine drink.

Tequila and Mezcal These spirits are distilled from the carbohydrate-rich heart of certain Mexican species of the agave, a succulent plant in the Amaryllis family that resembles a cactus. Tequila is made mainly by large distilleries around the northerly city of Jalisco from the blue agave, Agave tequilana, while the more rustic mezcal is made by small producers around central Oaxaca from the maguey, Agave angustifolia.

The agave stores its energy in the sugar fructose and the long fructose chains called inulin (p. 805). Because humans lack an enzyme for digesting inulin, people have learned to cook inulin-rich foods for a long time at a low temperature, a treatment that breaks the chains into their component sugars, and also develops an intense and characteristic browned flavor. Tequila makers steam the inulin-rich agave hearts, which may weight 20–100 lb/9–45 kg, while mezcal producers roast them in large charcoalfired pit ovens and generate smoky aromas that carry over into the spirits. The cooked, sweet hearts are then mashed with water and fermented, and the resulting alcoholicliquid distilled. Tequila distillation is industrial; mezcal is double-distilled, first in small clay pots, then in a larger metal pot still. Most tequila and mezcal is bottled without aging.

Tequila and mezcal have distinctive flavors that include roasty aromas, but also flowery ones (linalool, damascenone, phenylethyl alcohol), and vanilla (vanillin).

Flavored Alcohols: Bitters and Liqueurs Alcohol’s split chemical personality, its resemblance to fats as well as water, makes it an excellent solvent for other volatile, aromatic molecules. It does a good job of extracting and holding flavors from solid ingredients. Herbs, spices, nuts, flowers, fruits: all these and more are soaked in alcohol, or distilled along with alcohol, to make a host of flavored liquids. Gin is the best known of these. Most of the others fall into two families: bitters, which are just that, and liqueurs, which are sweetened to varying degrees with sugar.

Bitters Bitters are modern descendents of medicinal herbal brews that were first made with wine. Purely bitter ingredients include angostura (Galipea cusparia), a South American relative of the citrus family, Chinese rhubarb root, and gentian (Gentiana species); plant materials that are both bitter and aromatic include wormwood, chamomile, bitter orange peel, saffron, bitter almond, and myrrh (Commifera molmol). Most bitter alcohols are complex mixtures. They may be made by macerating the plant material or by distilling it along with the source of alcohol. Among the bitters commonly used today are Angostura and Peychaud’s bitters, condiment-like 19th century formulations that are added to mixed drinks and foods as a flavor accent, and such drinkable aperitifs and digestifs as Campari (unusually sweet) and Fernet Branca.

Liqueurs Liqueurs are a distilled alcohol sweetened with sugar and flavored with herbs, spices, nuts, or fruits. The flavoring agents may be extracted by soaking in the distilled alcohol, or they may themselves be distilled along with the alcohol. Most liqueurs have a neutral grain alcohol as their base, but there are a few whose base is a brandy or whisky. Examples are Grand Marnier, Cognac plus orange peel; Dram-buie, Scotch whisky plus honey plus herbs; and Southern Comfort, bourbon whiskey plus peach brandy and peaches. Some liqueurs include stabilized cream.

Anise and Caraway Alcohols These spirits get their dominant flavor from the seeds of plants in the carrot family, and may be either sweet or dry. Anise is especially popular; there are French, Greek, Turkish, and Lebanese versions among others (pernod and anisette, ouzo, raki, araq). Caraway seeds flavor dry Scandinavian aquavits and the sweet German Kümmel. When clear anise alcohols are diluted with clear liquid water or ice cubes that melt, the mixture becomes surprisingly cloudy. This is because the aromatic terpene molecules are insoluble in water, and soluble in alcohol only when the alcohol is highly concentrated. As the alcohol becomes diluted, the terpenes separate from the continuous liquid into little water-avoiding droplets, and these scatter light like the fat globules in milk.

Vinegar

Vinegar is alcohol’s fate, the natural sequel to an alcoholic fermentation. Alcohol makes a liquid more resistant to spoilage because most microbes can’t tolerate it. But there are a few important and ubiquitous exceptions: bacteria that can use oxygen to metabolize alcohol and extract energy from it. In the process they convert it to acetic acid, which is a far more potent antimicrobial agent than alcohol, and came to be one of the most effective preservatives of ancient and modern times. Alcoholic wine thus becomes pungently acidic wine: in French, vin aigre.

An Ancient Ingredient

Because fermented plant juices naturally turn sour with acetic acid, our ancestors discovered wine and vinegar together. In fact, a major challenge in winemaking was to delay this souring by limiting the wine’s exposure to the air. The Babylonians were making vinegar from date wine, raisin wine, and beer around 4000 BCE. They flavored their vinegar with herbs and spices, used it to pickle vegetables and meats, and added it to water to make it safe to drink. The Romans mixed vinegar and water to make an ordinary drink called posca, pickled vegetables in vinegar and brine, and judging by the late Roman recipe book of Apicius, often enjoyed vinegar in combination with honey. Pliny said that “no other sauce serves so well to season food or to heighten a flavor.” In the Philippines there developed a tradition of serving a variety of uncooked fish, meats, and vegetables in vinegar made from palm sap and tropical fruits. And the Chinese evolved dark, complex vinegars from rice, wheat, and other grains, which are sometimes roasted before fermentation.

For millennia, vinegar was made simply by allowing partly filled containers of wine and other alcoholic liquids to sour, an unpredictable process that took weeks or months. The first system for more rapid production, a bed of grapevine twigs over which the wine was regularly poured to aerate it, was invented in France in the 17th century. In the 18th a Dutch scientist, Hermann Boerhaave, introduced the continuous trickling of wine over an aerating bed. In the 19th century, Louis Pasteur demonstrated the essential roles of microbes and oxygen in the traditional Orléans process (p. 773). Modern methods for growing baker’s yeast and producing penicillin were adapted to vinegar manufacture after World War II, and now produce finished vinegar in a day or two.

The Virtues of Acetic Acid

Acetic acid contributes two different flavor elements to foods. One is its acidity on the tongue, and the other is its characteristic aroma in the nose, which can intensify to a kind of startling pungency, particularly when the vinegar is heated. The vinegar molecule can exist in two forms: as the intact molecule, and broken into its main portion and a free hydrogen ion. The hydrogen ion gives the main impression of acidity, while only the intact molecule is volatile and can escape from the vinegar or food, travel through the air, and reach the nose. Both the intact and “dissociated” forms coexist side by side, in proportions that are determined by their chemical surroundings. If the food is already acidic — thanks to the presence of tartaric acid in wine vinegar, for example — then less of the acetic acid dissociates, more is intact and volatile, and the vinegar aroma is stronger.

Acetic acid is an especially effective preserving agent. A solution as weak as 0.1% — the equivalent of a teaspoon of standard-strength vinegar in a cup of water/5 ml in 250 ml — will inhibit the growth of many microbes.

Acetic acid has a higher boiling point than water, 236ºF/118ºC. This means that vinegar will get more concentrated if it’s boiled. Because half of its molecule is more fat-like than water-like, it is a better solvent than water for many chemical relatives of fats, including the aroma compounds in herbs and spices. This is why cooks flavor vinegars by steeping herbs and spices in them, and why vinegar can help remove greasy films from various surfaces.

The Acetic Fermentation

It takes three ingredients to make vinegar: an alcoholic liquid, oxygen, and bacteria of the genus Acetobacter or Gluconobacter, mainly A. pasteurianus and A. aceti. These bacteria are among the few microbes that are able to use alcohol as an energy source. Their metabolism of alcohol leaves behind two by-products, acetic acid and water.

CH₃CH₂OH + O₂ CH₃COOH + H₂O

Alcohol + oxygen acetic acid + water

Acetic acid bacteria require oxygen, and so live on the surface of the fermenting liquid, where with other microbes they form a film sometimes called the “mother.” Especially thick films are created by Acetobacter xylinum, which secretes a form of cellulose. (Such mats are sometimes cultivated and eaten for themselves; see p. 509.) Acetobacteria thrive in warm conditions, so vinegar fermentations are often carried out at relatively high temperatures, from 82 to 104ºF/28–40ºC.

The concentration of alcohol in the starting liquid affects the acetic fermentation and the stability of the resulting vinegar. An alcohol concentration around 5% will produce a vinegar that is around 4% acetic acid, which is strong enough to prevent the vinegar solution itself from spoiling. Above 5% alcohol, the resulting vinegar will be stronger in acetic acid and so more stable, but the fermentation proceeds more slowly because the high alcohol levels inhibit the activity of the bacteria. For this reason, and to minimize residual alcohol in the finished vinegar, wines of 10–12% alcohol are usually diluted with water before acetic fermentation. However this also dilutes the wine’s flavorful components; so patient vinegar makers may still choose to ferment their wine straight.

Vinegar Production

There are three standard ways of producing vinegar in the West.

The Orléans Process The simplest, oldest, and slowest method was perfected in the Middle Ages in the French city of Orléans, where spoiled barrels of Bordeaux and Burgundy wine on their way to Paris were identified and salvaged as vinegar. In the Orléans process, wood barrels are partly filled with diluted wine, inoculated with a mother from a previous batch, and allowed to ferment. Periodically, some vinegar is drawn off and replaced by new wine. This method is slow, because the transformation of alcohol to acetic acid is limited to the wine surface exposed to the air. But the slow fermentation leaves time for reactions among the alcohol, acetic acid, and other molecules, and produces the finest flavor. When optimized, this process can yield a barrel full of vinegar in two months.

Streamlined Trickling and Submerged Cultures In the second, “trickling” method, the wine is poured repeatedly over a porous, air-rich matrix — wood shavings, or a synthetic material — onto which the acetic bacteria cling. This greatly increases the effective surface area of the wine, and regularly exposes all parts of the liquid to both oxygen and bacteria. The result is a quick fermentation that takes only a few days. Finally, there is the “submerged culture” method, in which free-swimming bacteria are supplied oxygen in the form of air that is bubbled through the tank. This industrial method converts the liquid’s alcohol into acetic acid in 24–48 hours.

The intact acetic acid molecule, and the acid dissociated into its acetate and hydrogen ions. Only the intact molecule is volatile and detectable in the nose by its distinctive smell. Adding vinegar to an alkaline ingredient — egg whites or baking soda, for example — causes the acetic acid molecules to dissociate, and diminishes its aroma.

After Fermentation After fermentation, nearly all vinegars are pasteurized at 150–160ºF/65–70ºC to kill remaining bacteria of all kinds, but especially the acetobacteria themselves, which respond to the disappearance of the alcohol by metabolizing acetic acid to water and carbon dioxide and thus weakening the vinegar. Most vinegars are aged for a few months, a period in which their flavor becomes less harsh and more mellow, thanks in part to the combination of acetic and other acids with various compounds to form new, less pungent, often aromatic substances.

Common Kinds of Vinegar

Cooks can choose among several different kinds of vinegar. Though all have the basic aroma and pungency of acetic acid, each is distinctive, because they’re made with different starting materials, and may or may not be matured in wood.

Wine Vinegars Wine vinegars are made from a base of yeast-fermented grape juice. They therefore have a winey character from the aromatic and savory by-products of the yeast fermentation. Interestingly prominent in wine and cider vinegars are buttery aroma compounds (diacetyl, butyric acid). Balsamic and sherry vinegars are specialized versions of wine vinegar (see pp. 775–776).

Cider Vinegars Cider vinegar is made from a base of yeast-fermented apple juice. It therefore includes some of the characteristic aroma components of apples, and others that are especially accentuated in apple fermentation; these include the volatile phenols that give animal and stable aromas to grape wines (ethyl guaiacol and ethyl phenol, p. 738). Apples are rich in malic acid, so cider vinegars undergo a malolactic fermentation (p. 730) that may augment aroma while softening acidity. Thanks to its pulp and tannin content, cider vinegar often becomes cloudy with tannin-protein complexes.

Fruit Vinegars Fruit vinegars may simply be ordinary vinegars flavored by contact with fresh fruit, including apples, but they’re also made by fermenting the fresh fruit juices. Pineapple and coconut vinegars are examples. Fruit vinegars are interesting for their expression of the fruit’s flavor through the alcoholic and acetic fermentations.

Malt Vinegars Malt vinegar is essentially made from unhopped beer: that is, from cereal grains and sprouted barley. It has overtones of barley malt. This was the standard form of vinegar in beer-drinking Britain, where it was originally called alegar.

Asian Vinegars Asian rice and grain vinegars are made from grains whose starch is broken down to sugars by means of a mold culture rather than sprouted grains (p. 753). Chinese vinegars can be especially flavorful and savory because they’re made from whole, sometimes roasted grains, fermented in continuous contact with the grain solids, and often aged in contact with the molds, yeasts, and bacteria, all of which release amino and other organic acids and other flavor compounds into the vinegar.

White Vinegars White vinegar is among the purest sources of acetic acid. It’s made by acetic fermentation of pure alcohol that has been either distilled or synthesized from natural gas, and is not aged in or softened by contact with wood. It contains few or none of the aromatic and savory byproducts of the alcoholic fermentation. In the United States, more white vinegar is made than any other kind. It’s used mainly in the manufacture of pickles, salad dressings, and mustards.

Distilled Vinegars Distilled vinegar in the United States is white vinegar made with distilled alcohol; in the United Kingdom, it’s vinegar that is made by acetic fermentation of unhopped beer, and then distilled to concentrate the acetic acid.

Vinegar Strength When developing and following recipes in which vinegar is a prominent ingredient, cooks should take care to note not only the kind of vinegar, but also the strength, which is usually indicated on the label. In the United States, most industrially produced vinegars are adjusted to 5% acetic acid, but many wine vinegars are 7% or even stronger. Mild Japanese rice vinegars, by contrast, may be 4% (the U.S. minimum), black Chinese vinegars as little as 2%. A spoonful may thus provide half as much acetic acid as expected, or twice as much, depending on the vinegars that are called for and actually used.

Balsamic Vinegar

True balsamic vinegar, aceto balsamico, is a vinegar like no other: almost black in color, syrupy, sweet, remarkably complex in flavor, and remarkably expensive, all thanks to decades-long fermentation, aging, and concentration in wood casks. It has been made in the northern Italian state of Emilia-Romagna since medieval times. Individual households produced their own as a kind of general-purpose, soothing tonic, or balsam. It wasn’t until the 1980s that the rest of the world discovered balsamic vinegar, a discovery that fostered the development of less elaborate and less costly approximations. The label term tradizionale, “traditional,” is reserved for the original version.

Making Traditional Balsamic Vinegar Traditional balsamic vinegar begins with wine grapes: white Trebbiano, red Lambrusco, and a number of other varieties are used. Their juice is boiled until the volume is reduced by about a third. Boiling removes enough water to concentrate the juice to around 40% dissolved sugars and acids, and begins the sequence of browning reactions between sugars and proteins that generate both rich flavor and color (p. 778). The juice is then placed in the first of a sequence of progressively smaller barrels, often made from a variety of woods (oak, chestnut, cherry, juniper), which are kept in an attic or other location where they’re exposed to the variations and extremes of the local climate. In summer heat, the concentrated sugars and amino acids react with each other to produce aroma molecules more commonly found in roasted and browned foods, and the fermentation products and by-products react with each other to form a heady mixture. As evaporation continues to remove water and concentrate the must (about 10% of the barrel disappears each year), each barrel is replenished with must from the next younger barrel. Finished vinegar, whose average age must be a minimum of 12 years, is removed from the oldest barrel. According to one estimate, it takes about 70 lb/36 kg of grapes to make 1 cup/250 ml of traditional balsamic vinegar.

Notice that there’s no initial alcoholic fermentation before the acetification begins. Instead, a mixed culture of yeasts and bacteria simultaneously converts a portion of the abundant grape sugars into alcohol, and that alcohol into acetic acid. These conversions proceed slowly, over the course of several years, because the high concentration of grape sugars and acids inhibits the growth of all microbes. The alcoholic fermentation is carried out by unusual yeasts, Zygosaccharomyces bailii or bisporus, that are adapted to surviving in environments high in sugars and in acetic acid. At the same time that the two fermentations take place, so do the processes of maturation and aging.

In the end, traditional balsamic vinegar may contain anywhere from 20 to 70% unfermented sugars, about 8% acetic and 4% tartaric, malic, and other nonvolatile acids, an aroma-enhancing 1% alcohol, and up to 12% glycerol, a product of the yeast fermentation that contributes to the velvety viscosity.

The “condiment” grades of balsamic vinegar are made much more rapidly than the traditional grade, and are far less concentrated and fine-flavored. The better mass-produced vinegars include some cooked-down grape must and young balsamic vinegar, and are aged for a year or so. Cheap balsamic vinegars are no more than ordinary wine vinegar colored with caramel and sweetened with sugar.

Sherry Vinegar

A style of vinegar that lies somewhere between ordinary wine vinegar and balsamic vinegar is the solera-aged sherry vinegar of Spain. This starts from the young sherry wine, which contains no residual sugar. Like sherry wines and balsamic vinegars, sherry vinegar is blended with older batches and matured for years or decades in a series of partly-filled barrels. The concentration by evaporation, and extended contact with microbes and wood, leave sherry vinegar with high levels of savory amino acids and organic acids, and viscous glycerol. In old soleras, the acetic acid concentration can reach 10% and more. Sherry vinegar isn’t as dark and savory as balsamic vinegar, but is noticeably more intense and nutty than other wine vinegars.