Cooking is all about the transformation of ingredients, and one of the most important transformations takes place when ingredients make the journey, via heat, from soft, pale, and wan to lusty, crusty, and golden brown. So many foods—from fish fillets to apple fritters—develop a beautiful brown exterior when properly cooked, which makes them appealing to look at and, more important, much more flavorful and pleasantly textured.
This type of browning—which produces crusty brown loaves of bread, crisp cookies, the crunchy brown coating of fried food, the rich brown glaze of a roast, or the gutsy brown grill marks on a steak—is nonenzymatic browning, caused by reactions of proteins and certain sugars with heat. (This is different from the less desirable browning caused by enzymes—for example, when fruit is cut or bruised and the phenolic compounds react with the oxygen in the air.)
Nonenzymatic browning can occur two ways: the simple browning of sucrose (white sugar) at high temperatures, and the more complex browning of certain sugars and proteins at lower temperatures.
The first type of browning is true caramelization. When you cook sucrose to very high temperatures (over 300°F), it melts and then starts to caramelize (or decompose). During this process, different sugars form, break apart, and some of these new sugars rejoin. At any point between clear melted sugar and dark caramel, there is a different mixture of sugars; more than 128-different sugars have been identified. Many of these are brown in color and have the wonderful taste that we associate with caramel, so when this reaction is carefully controlled, you can enjoy caramel sauce, caramel candies, and caramel flavoring in desserts or even in savory dishes.
The second kind of browning, called the Maillard reactions (named for the chemist who first described them), is a series of complex reactions that produce essentially the same sweet brown compounds that you get in caramel, plus many others. Everything from toast to fried chicken and roast beef gets this rich-tasting brown coating from the complex reactions that occur when proteins and certain sugars are heated.
These Maillard reactions differ from simple caramelization (though the two types of browning can take place at the same time) in that they require several ingredients, not just table sugar. Although accelerated by heat, they can occur at low temperatures—even as low as room temperature. Four conditions are necessary for this browning:
- a nonacidic environment (conditions below pH-7—a measure of acidity—are acidic. Ideal conditions for browning are pH-7.8 to pH-9.2);
- the presence of proteins;
- the presence of certain types of sugar (called reducing sugars, of which corn syrup is the most familiar example); and
- a low to medium moisture level (foods won’t brown if they are very wet). As long as the acidity and moisture are low, the more protein and the more reducing sugars present, the browner the food will get.
Sometimes you need to make your food browner, for example, when cookies are actually fully cooked but they still look a little too blond and bland. In other cases, browning may occur too quickly, for example with battered onion rings: the batter may be dark brown but the onions inside are still raw and sharp-tasting.
You can boost or tone down the Maillard reactions by manipulating acid, proteins, and sugar. I’ve suggested ways to do this in the charts at left.
What to do for more browning
- For roasted poultry , make a basting liquid of a little corn syrup (which contains glucose, a reducing sugar), butter (which has both proteins and sugars from the milk), and consommé (the stock and the gelatin in consommé both add protein).
- For roasted meats, near the end of cooking time, raise the temperature of the oven to get fast browning. By then, lots of the juices (which contain sugars and proteins) have evaporated on the surface of the meat so it will brown well.
- For cookies, add a little more baking soda (to reduce the acidity) than you need for leavening, which is about 1/4-teaspoon per cup of flour. The cookies won’t puff more, but they’ll get darker faster.
- For cookies and other baked goods, use a higher protein flour (unbleached instead of bleached, all-purpose instead of cake flour, or bread flour instead of all-purpose). Alternatively, substitute corn syrup (glucose) or an egg yolk or milk (protein) for part of the liquid in the recipe.
To reduce or delay browning
- For pie crusts that must bake a long time, like in a pecan pie, use a lowprotein flour (cake flour or bleached all-purpose), eliminate sugar in the crust, and maybe add a teaspoon of vinegar or lemon juice.
- For deep-fried foods, eliminate sugar in the batter and use a lowprotein flour or cornstarch for the batter or for dusting. In doughs that require high-protein flour, like a beignet, add a little lemon juice or vinegar to the batter to make it more acidic.
- For roasting or grilling, brush only with oil to slow browning.
- For cookies, use cake flour or acidic ingredients like vinegar, lemon juice, or cream of tartar.