Leaveners work by incorporating air into a batter (in the case of beaten eggs) or creating carbon dioxide in a batter (in the case of baking soda and baking powder). As the batter heats during the cooking process, the gas expands making the product rise, and the flour mixture firms up, creating a structure that holds, even after the baking process ends and the food cools.
Eggs, baking soda and baking powder all work in different ways to leaven baked goods.
With eggs, the process is mechanical. When you beat eggs, especially egg whites, they puff up because of the air bubbles that are created. In some cakes whole eggs are beaten into a creamed mixture of butter and sugar as well. Instructions say to “beat until fluffy”, and this means “continue beating until the mixture visibly increases in volume and becomes lighter in colour”.
Heavier ingredients such as flour are added to a mixture that is leavened with beaten eggs by folding in, a technique intended to break as few air bubbles as possible. To fold in, use a rubber spatula or a spoon, gently cut downward through the batter and then lift it slowly to the top.
Adding a pinch of an acidic ingredient, such as cream of tartar (tartaric acid), to egg whites makes them more stable when beaten. Often sugar is beaten in gradually after egg whites have reached the soft peak stage, making the foam more stable and easier to spread.
The presence of fat, even a small amount on a greasy bowl (more likely to happen with plastic and therefore it’s best to use either glass or stainless steel) will reduce the volume that egg whites reach when beaten. It is the fat in the egg yolk that creates difficulty if even a drop of yolk gets into egg whites before they are beaten.
Baking soda, also called bicarbonate of soda, is alkaline and releases carbon dioxide gas when it comes into contact with an acidic ingredient. This is what creates those entertaining volcanoes that children create using baking soda and vinegar.
Soda is used as a leavener in conjunction with acidic foods including buttermilk, natural cocoa powder (not Dutch process cocoa, which is not acidic), lemon juice, molasses or vinegar, in foods such as buttermilk pancakes and the cake recipe that follows.
When baking soda comes into contact with acidic ingredients, the reaction is immediate. You have to be ready to bake these mixtures immediately after mixing, before there is time for the bubbles to burst, or they will not rise as expected.
Baking powder is a mixture containing baking soda, and inert powder such as cornstarch and at least one acidic ingredient. When dry, the soda and acid do not react, but the reactions begin when liquid is added.
Most baking powder sold now is the double acting type, which contains 2 acidic ingredients. One of them reacts with the soda as soon as liquid is added, and the other reacts when the mixture is heated. That two-stage reaction makes it a more forgiving way to leaven foods than using baking soda and acid, which reacts all at once.
Deep Chocolate Vegan Cake
Adapted from a Moosewood book, via recipezaar.com
375 mL (1½ cups) all purpose flour
75 mL (⅓ cup) unsweetened natural cocoa powder
2 mL (½ tsp) baking soda
2 mL (½ tsp) salt
250 mL (1 cup) sugar
125 mL (½ cup) vegetable oil
250 mL (1 cup) cold water or chilled brewed coffee
10 mL (2 tsp) vanilla extract
25 mL (2 tbsp) cider vinegar
Preheat oven to 190 C (375 F).
Oil a 20 cm (8 inch) square or round cake pan, and dust with sifted cocoa.
Sift together flour, cocoa, soda, salt and sugar.
In another bowl, mix oil, water and vanilla.
Pour liquid into dry and mix until smooth.
Add vinegar and stir briefly. Immediately pour batter into prepared pan, and bake 25-30 minutes.
Margaret Prouse, a home economist, can be reached by writing her at RR#2, North Wiltshire, P.E.I., C0A 1Y0, or by email at firstname.lastname@example.org.