A few days ago, a friend and avid baker, called me and rattled on a list of ingredients she had gotten from the bakery where she purchased a gluten-free coconut cake and asked me to give her proportions that would work so she could replicate it at home. Together, we approximated measures that could potentially work and started talking about baking soda and baking powder, whether to add one or both, although not mentioned in the ingredients’ list. “I am not sure how they work”, she mused, so I thought I would put together an easy primer for her.
The role of leaveners in baking is, clearly, to make baked goods rise. They all achieve the same effect by introducing carbon dioxide into a batter or dough. There are three different types of leaveners.
By far the most used by home cooks, these comprise baking soda and baking powder. They both work because an alkaline ingredient (such as sodium bicarbonate, the real name of baking soda) interacts with an acid. In the case of baking soda, the acid can be an ingredient such as buttermilk, kefir, sour cream, yogurt or chocolate (not Dutch processed). With baking powder, the alkaline is already contained in the packaged powder we get at the market. The combination of alkalis and acids create carbon dioxide in the presence of liquids which, with heat, expands the batter. These doughs and batters are called quick breads because the leavening process happens quickly.
If you have ever wondered what “double acting” means on the baking powder box in your kitchen, it refers to the double reaction that occurs when the powder is mixed in your batter: it reacts first when mixed with the liquids and, secondly, in the presence of heat. And if you are not sure how much baking soda to add to a recipe that contains an acid, a good rule of thumb is 1/2 ts (or 2 mg) per 1 cup (240 ml) of acid liquid.
We are talking about yeasts here, living organisms that feed on sugars, thereby producing carbon dioxide and alcohol. Mainly used for bread or yeasted doughs such as brioche, they take a long time to act and their temperature needs to be controlled. Yeasts will not work below 65 F (18C) or above 140F (60C). Sourdough starter is another natural yeast and it’s obtained by “souring” flour and water over the course of days or weeks. Regular feeding of water and flour can keep the yeast alive for years.
Steam is a leavener that follows the laws of physics – think souffle. Heat causes air pockets that expand the batter. It also plays a vital role in laminated doughs (puff pastry, croissants and Danish pastry): the steam is trapped between the layers of dough, causing them to separate and rise. Air is also a rising agent – we whip or cream certain ingredients such as egg whites by incorporating large amounts of air before adding them to the final batter.
PS The sources I used to express in words what I do every day were “The Culinary Institute of America – Professional Chef” and Harold McGee’s “On Food and Cooking”.