A Note About Units of Measurement,
and About the Drawings of Molecules

Throughout this book, temperatures are given in both degrees Fahrenheit (ºF), the standard units in the United States, and degrees Celsius or Centigrade (ºC), the units used by most other countries. The Fahrenheit temperatures shown in several charts can be converted to Celsius by using the formula ºC = (ºF-32) x 0.56. Volumes and weights are given in both U.S. kitchen units — teaspoons, quarts, pounds — and metric units — milliliters, liters, grams, and kilograms. Lengths are generally given in millimeters (mm); 1 mm is about the diameter of the degree symbol º. Very small lengths are given in microns (µ). One micron is 1 micrometer, or 1 thousandth of a millimeter.

Single molecules are so small, a tiny fraction of a micron, that they can seem abstract, hard to imagine. But they are real and concrete, and have particular structures that determine how they — and the foods made out of them — behave in the kitchen. The better we can visualize what they’re like and what happens to them, the easier it is to understand what happens in cooking. And in cooking it’s generally a molecule’s overall shape that matters, not the precise placement of each atom. In most of the drawings of molecules in this book, only the overall shapes are shown, and they’re represented in different ways — as long thin lines, long thick lines, honeycomb-like rings with some atoms indicated by letters — depending on what behavior needs to be explained. Many food molecules are built from a backbone of interconnected carbon atoms, with a few other kinds of atoms (mainly hydrogen and oxygen) projecting from the backbone. The carbon backbone is what creates the overall structure, so often it is drawn with no indications of the atoms themselves, just lines that show the bonds between atoms.