Part II — The Big Molecules: Proteins, Carbohydrates, and Fats

Here is a small kitchen mystery worth pausing on.

When you sear a steak in a hot pan, the surface turns brown and develops a flavor that did not exist in the raw meat. When you toast a slice of bread, the surface turns brown and develops a flavor that did not exist in the dough. When you roast coffee beans, the surface turns brown and develops a flavor that did not exist in the green bean. When you grill an onion until the edges blacken, the same thing happens. When you fry a tortilla. When you bake a cookie. When you brew dark beer. When you roast a marshmallow. When you toast almonds.

Brown food. Complex flavor. Delicious.

The mystery is not that all these foods get brown and delicious. The mystery is that they do it for the same reason, by the same chemical reaction, discovered by the same Frenchman, named after the same man — Louis-Camille Maillard, 1912. Steak, bread, coffee, beer, cookies, marshmallows. Different foods. Same reaction. Once you can see it, you cannot unsee it.

This is the gift of Part II. We are about to spend seven chapters on three molecules: protein, carbohydrate, and fat. Three. That's it. And from these three molecules — plus a few enzymes, a little air, and some heat — comes essentially every food humans cook. The plate of dumplings. The bowl of dal. The soufflé. The slice of pizza. The square of chocolate. The mug of beer. All of it is some arrangement of these three molecules undergoing a small set of reactions you can learn by name.

What lives in this part

Seven chapters, structured as a tour of the three big macronutrients and the chemistry that builds color, texture, and aeration from them.

Chapter 7. Proteins. Long folded chains of amino acids that come undone when you heat them, or salt them, or whip them, or splash acid on them. The egg white that goes from clear and runny to white and firm is a protein chain unfolding and tangling with its neighbors. We start with the egg because the egg is the universal lesson — every protein concept in the book lives inside one shell.

Chapter 8. The Maillard Reaction. The brown-and-delicious reaction. Amino acids (from proteins) plus reducing sugars (from carbohydrates) plus heat plus a little time, producing literally hundreds of new flavor and aroma compounds. Maillard runs in the steak, the toast, the roast coffee, the beer mash, the chocolate roast. Learn it once. Recognize it everywhere.

Chapter 9. Carbohydrates and Starches. The molecules that thicken sauces, fluff rice, give bread its crumb, and stiffen overnight in your fridge. Starch granules are tiny packed structures that swell and burst and release their innards into your gravy — and then, after a day in the cold, slowly retighten in a process called retrogradation, which is why day-old rice is hard and yesterday's bread is stale.

Chapter 10. Sugars and Caramelization. Caramel is what happens when sugar cooks alone, with no protein involved — different from Maillard, often confused with it, beautiful in its own right. Hard candy, fudge, butterscotch, the dark crust on a crème brûlée. Caramelization gives you the temperature ladder candy makers have lived by for two centuries.

Chapter 11. Fats and Oils. Saturated, unsaturated, smoke point, melting point, emulsion. Fat is the flavor solvent of the kitchen — most of what we call "delicious" is fat-soluble. Mayonnaise is fat held in water by an egg yolk. Hollandaise is the same trick with butter. Vinaigrette is the trick failing on purpose. The science is identical across all three.

Chapter 12. Foams and Aeration. Whipped cream, meringue, soufflé, beer head, marshmallow, the bubbles in bread dough. A foam is gas trapped in liquid stabilized by a surfactant — and the surfactant is almost always either a protein (egg whites) or a fat (heavy cream). The reactions you learned in chapters 7 and 11 come back, doing different work, in your stand mixer.

Chapter 13. Enzymes. Biology's catalysts. The reason pineapple eats Jell-O, the reason a steak left to age gets tender, the reason malted flour browns more enthusiastically than unmalted, the reason cheese exists at all. Enzymes are proteins (back to Chapter 7) that speed up specific reactions — and they are everywhere in the kitchen, often working without our knowledge.

The pattern

Read these chapters in order if you can. Each one builds on the last. By the end of Chapter 13 a pattern will have emerged that is, I think, one of the most satisfying things in food science: the same reactions appear everywhere.

Maillard browns the steak (Chapter 8) and the bread crust (Chapter 17, in the next part) and the coffee bean (Chapter 21) and the chocolate (Chapter 20). Emulsification holds together mayonnaise (Chapter 14) and butter (Chapter 16) and ice cream (Chapter 28) and vinaigrette (Chapter 11). Protein denaturation cooks the egg (Chapter 14) and the steak (Chapter 15) and the cheese curd (Chapter 16) and the meringue (Chapter 12). Starch gelatinization thickens the gravy (Chapter 9) and softens the rice (Chapter 17) and gives bread its crumb (Chapter 17) and stiffens the pudding (Chapter 16).

Five reactions. Maybe ten. They run the entire kitchen.

Danny Reyes-Park, who is studying food science in Chicago and works weekends at a fermentation-focused restaurant, has been keeping a notebook for two years now. The notebook lists every dish he has cooked or watched cooked, and beside each one, the reactions involved. Maillard. Emulsification. Denaturation. Gelatinization. Caramelization. The list does not get longer over time. The list of dishes does. He told me once that the moment the notebook stopped accumulating new reactions and started accumulating new applications was the moment he understood food science was not infinite. It was finite, and gorgeous, and the same in every kitchen on earth.

That is the gift waiting for you in this part. Not a list of recipes. A list of reactions, each of which appears in dozens of recipes you already know.

A small piece of advice before we begin. The chemistry in these chapters is the chemistry of cooking, not the chemistry of textbooks. If you have an instinct that says "I am going to be lost," ignore it. We will tell you what to look at, what to smell, and what to taste. The molecules are large, but the ideas are small. Heat unfolds protein. Sugar plus protein plus heat goes brown. Fat carries flavor. Three sentences. The whole part is sitting inside them.

Take a breath. Turn the page. Chapter 7: the protein, and the egg.

Chapters in This Part