Chemical Leaveners: Baking Soda and Baking Powder

By Miranda Kohout

When we reach for baking soda or baking powder, it’s a casual move, not one imbued with reverence for the history and chemical wonder contained in these seemingly simple white powders, but their simple appearance is deceptive. As we have seen with other ingredients, successful baking and pastry are all about chemistry. While an egg yolk or spoonful of cocoa powder might not call to mind a science lab, baking powder and baking soda are added to recipes for their chemical properties. In fact, the term “chemical leavener” is often applied to these two ingredients and distinguishes them from the “natural leavener,” yeast.

Ad executives and influencers have given the terms “natural” and “chemical” so much weight that it is important to take a moment to divorce these words from any morality they may have implied. “Chemical” does not mean bad or dangerous and “natural” does not mean good or safe. Everything around us, including many natural things, have chemical properties.

Purpose of Chemical Leaveners

Both baking soda and baking powder play several roles in baked goods and even in confectionary, but their primary purpose is to add air to baked items and create a light, spongy texture. Historically, this role was filled by pearlash (potassium carbonate), hartshorn (ammonium bicarbonate) or hours of whipping and beating by hand, all of which have drawbacks that range from mild to considerable. Yeast has also contributed its leavening power to items such as cakes, but it isn’t well-suited for the task, adding air too slowly to leaven most items before their proteins and starches have set.

Types of Chemical Leaveners

Baking Soda

The simpler of the two common chemical leaveners, baking soda comprises a bicarbonate and a carrier molecule. In most cases, the carrier is sodium, a natural fit for cooking. When baking soda is combined with a liquid, the bicarbonate dissolves and becomes available to react with acids and generate CO2 – gassy bubbles that, once trapped in a cake or muffin’s structure, give us the light texture and airy crumb sought in most versions of these products.

Baking Powder

When a batter or dough contains little or no acid, baking powder, the more complex leavener, provides both the acid and the base needed to create carbon dioxide bubbles. At its simplest, baking powder can be made of bicarbonate and an acid. This is why, if you find yourself in a pinch, you can make an ersatz baking powder from baking soda and cream of tartar.

You might then wonder if a commercial version of baking powder is truly necessary. Double-acting, commercial baking powder contains at least two different acids in addition to the bicarbonate. With its single acid and quick reaction, our DIY baking powder expands 75% of its leavening power before the item enters the oven. Different acids have different reaction rates and react at different temperatures, so commercial manufacturers create specific blends of acids to help bakers achieve the best possible results. Baking powders are called “double- acting” because the first acid “acts” once combined with the liquid in the recipe; then the second acid becomes available to react in the heat of the oven.

Large industrial bakeries, with access to a wide range of different acids, will even blend a proprietary baking powder tailored to their recipes and equipment.

Single-Acting Baking Powder

A double-acting baking powder’s second, slower-acting acid is often aluminum-based. Some chefs prefer to avoid aluminum and will opt for a non-aluminum baking powder. These baking powders are generally single-acting. In these products, the only carbon dioxide- producing reaction occurs when you add liquid. They will perform comparably well in everything except dryer doughs, such as those used to make scones or biscuits, in which their leavening power falls short.

How Chemical Leaveners Lighten Baked Goods

We’ve mentioned that baking powder and baking soda create chemical reactions between bases and acids that then generate carbon-dioxide bubbles, thereby aerating and lightening our baked goods. It is crucial to note that leaveners do not create new air bubbles in a batter; rather, they enlarge the bubbles that already exist. Without pre-existing bubbles created by methods such as whipping or creaming to trap carbon dioxide, they would simply rise to the surface and dissipate as they do in a soft drink.

Other Functions of Chemical Leaveners

While we can easily observe the aerating effects of baking soda and baking powder in a cake or muffin, we can also consider cookies to spot the other ways in which chemical leaveners enhance baked goods. The amount of leaveners in a cookie recipe is minimal, not enough to provide much aeration, so this is an excellent place to study their other effects.

When baking soda interacts with acidic ingredients, the ingredients are neutralized as a result of the reaction, changing the dough’s overall pH from acidic to alkaline. Alkaline doughs brown faster and have a weaker gluten structure. The quintessential cookie is crumbly, not tough, and has a tempting, golden-brown color. While baking does not create cookie perfection on its own, its presence in a dough offers welcome enhancements.

You can also see the browning effect of baking soda in caramel or honeycomb candy. These mixtures will darken considerably with the addition of baking soda once the initial volcano-like chemical reaction has ceased.

Baking soda reacts immediately upon contact with liquid. Most cookie doughs are dry, relative to something such as cake batter, and no reaction will occur in a cookie dough until the batter has melted. An alkaline environment slows protein coagulation, so a cookie dough containing baking soda will have some time to spread in the oven before the eggs in the dough are set.

You don’t often use baking powder in cookie dough, but it can play a role. Unlike baking soda, baking powder contains the acid needed for a chemical reaction, so it will not impact the dough’s pH. The cookies will get a little aeration, and acid ingredients will remain to impact the final product. Acidic doughs will spread less than alkaline ones and brown less easily.

Bakers will observe a rise in cookies containing baking powder, but only up to a point. Too much baking powder will increase the size of the existing air bubbles to the extent that they become unstable and pop, creating a dense and craggy cookie.

Tips for Use and Troubleshooting

• While it’s true that both baking soda and baking powder can expire, improper recipe formulation, poor mixing or insufficient aeration are the more likely culprits when baked goods don’t rise.

• In a well-formulated recipe in which leavening is the goal, there will be a balance between the amount of baking soda and acid contained in the recipe. Too much baking soda results in a soapy taste. Too little baking soda in a recipe can leave some acid behind. Unlike the soapiness that results from too much baking soda, the acidic tang from yogurt or buttermilk can be a welcome flavor. For example, two grams of baking soda will neutralize 240 grams of buttermilk, but you can get great flavor from adding just one gram of baking soda for every 240 grams of buttermilk, with extra acid adding protein coagulation and improving the baked good’s color.

• Different ingredients have different acidity levels, so the buttermilk example above is by no means one-size-fits-all. The pH of coffee ranges from 4.4 to 4.8, and regular milk has a nearly neutral pH (6.7 to 6.9). When a recipe isn’t performing as expected and baking soda is the suspected culprit, the overall pH of the recipe should be the chef’s first concern.

• A good rule of thumb is to use no more than five to six grams of baking powder or one gram of baking soda for 125 grams of flour, though this will vary depending on the acidity of other ingredients.

• Pay special attention to cocoa powder. “Natural” cocoa powder is acidic, while “Dutched” cocao powder has been alkalized. Baking soda can neutralize all or part of the acid from non-alkalized cocoa, causing unexpected results if the recipe calls for Dutched cocoa.

• Uneven distribution of chemical leaveners can result in large, irregular air pockets intermixed with dense portions. While this is often attributed to poor mixing methods, it’s more likely that the baking soda or baking powder wasn’t evenly distributed among the dry ingredients. Simply whisking the dry ingredients in a stand mixer is the most effective way to ensure an even distribution.

• In self-rising flour, leaveners are distributed perfectly, and the particular combination of leaveners is carefully formulated for the low protein level of the flour and the typical make-up of the recipes for which the items are used. While many chefs may create an ad-hoc, self-rising flour when a recipe calls for it, the commercial version can offer superior results.

Trivia

While you might imagine baking soda being synthesized in a lab, almost all sodium bicarbonate comes from mines in Wyoming in the form of Trona ore.

(This article appeared in the Winter 2025 issue of Pastry Arts Magazine)