By Harold McGee
Cake bakers use low-protein pastry or cake flours to minimize the toughening that comes with gluten formation. They’re not really interchangeable; cake flours are both chlorinated and milled into very small particles to produce a fine, velvety texture. Cooks who prefer not to use cake flours can approximate their protein content and increase fineness by adding starch to all-purpose or pastry flours. Corn starch is the most commonly available starch in the United States; potato and arrowroot starches lack cornstarch’s cereal flavor and gelate at lower temperatures, which can reduce cooking times and produce a moister cake. Some cakes are made with pure starch or starchy chestnut flour only, and no wheat flour at all.