Leavening agents, baking soda

Baking soda, or sodium bicarbonate, is a pure chemical leavener rather than a food eaten on its own. Whisked into a batter or dough alongside an acidic ingredient like buttermilk, brown sugar, cocoa, honey or lemon juice, it reacts to release carbon dioxide bubbles that lift pancakes, quick breads, cookies and cakes as they bake. It works fastest once it meets both liquid and acid, so recipes that call for it are typically mixed and baked right away rather than left to sit. It's also used in small amounts to tenderize meat marinades and to help onions and other vegetables brown faster in a hot pan.

Keep the box tightly closed in a dry cabinet, since it absorbs moisture and odors readily; many cooks also keep a separate open box in the refrigerator to absorb stray smells, apart from the one used for baking, and swap it out every few months once it stops fizzing when tested in vinegar. It contributes 0 calories and no protein, fat or carbohydrate per 100g, so it plays no nutritional role in a dish. Per 100g it carries 27,400mg of sodium, though the small amount used per recipe, often under a teaspoon, contributes only a modest fraction of that to the finished dish. Because of its potency, recipes call for it in small, precisely measured amounts rather than to taste.