A friend asked me over the weekend if I knew the real difference between baking soda and baking powder. I replied that it was a very good question. I know that they both react with liquid, acid, and heat to cause whatever baked goods they’re in to rise. I also know that if you use too much baking soda in a recipe, your food will taste like soap.
But beyond that, I must admit, I never gave the difference much thought.
Well, now I have and I’ll share the answers to this question.
As always, I have turned to one of my all-time favorite books on baking, In The Sweet Kitchen, by Regan Daley (Artisan Books, 2001). If you don’t own this book and you enjoy or even simply interested in baking and making desserts, then, by all means, buy a copy. The first half of the book talks about method, ingredients, equipment, method, and technique. The second half is all about recipes. And they are wonderful.
All the following (paraphrased) information is from Ms. Daley’s book (pp. 194-7).
Baking powder and baking soda are what are known as “chemical leaveners”. These are used when the recipe isn’t suitable for a natural leavener (i.e. yeast) or mechanical methods (i.e. creaming, beating or whipping). Chemical leaveners (when fresh) also provide a much more reliable method of leavening. Many recipes with chemical leaveners also use some form of mechanical leavening, to ensure a lighter, more tender result.
Baking Soda: Baking soda is commonly used as a leavener in baked goods such as cakes, quick breads, and cookies. It has no leavening power on its own and must be activated by the presence of acid and liquid. These elements together help the baking soda release carbon dioxide in the form of air bubbles which helps the baked goods to rise.
Acids with the power to activate baking soda include cream of tartar, buttermilk, yogurt or sour cream, molasses, dark brown sugar, maple syrup, citrus juices, or even non-alkalized cocoa powder (not Dutch-processed). In some cases, although there is a moderately acidic ingredient in a recipe, it may not be acidic enough or a large enough quantity to provide the necessary leavening. Honey, light brown sugar, and cocoa may sometimes fall into this category. If this is the case, then baking powder is added to the recipe as well to provide the necessary leavening.
Baking soda releases carbon dioxide quickly once it is mixed with a liquid in the presence of an acid. So, be sure that the baking soda is mixed thoroughly with the dry ingredients before the liquid is added, pour the batter into the prepared pan and bake immediately. If too much time elapses, the carbon dioxide will dissipate and your recipe may not rise fully at all or not at all.
If you replace a non- or low- acid ingredient for an acidic ingredient in a recipe, you must replace introduce another acid (i.e. lemon juice or vinegar in sweet milk) or add baking powder to the recipe to achieve leavening.
A secondary function of baking soda is to neutralize acidic ingredients. For this reason it is sometimes used in recipes with a high proportion if ingredients like buttermilk, lemon juice, or other sour flavors. If you replace sugar with a large amount of an acidic sweetener, such as honey, molasses, or barley syrup, add an additional 1/2 teaspoon of baking soda to the recipe, even if it is the principal leavener.
The substitution ratio for baking soda to baking powder is 1:4. This means, for every 1 teaspoon of baking soda substituted, you use 4 teaspoons baking powder. However, baking powder will not neutralize the acidic flavor of some ingredients. So, the final product may taste more acidic than you like.
Baking soda will last 9 to 12 months when properly stored in a cool, dry place and in an airtight container (especially if you’re going to use it for baking). To test the potency of baking soda, combine equal quantities of soda and vinegar. If it bubbles vigorously, it’s good.
Be sure not to use the baking soda you use to neutralize the odors in your refrigerator or freezer. Since baking soda absorbs odors, it could be a rather rude surprise.
Baking Powder: Baking powder was originally a mix of baking soda (sodium bicarbonate), a moisture absorbing starch (usually cornstarch), and tartaric acid (cream of tartar). When introduced to liquid, the mixture releases carbon dioxide that produces air bubbles which leaven your baked goods. However this mixture, called “single action” baking powder, releases its carbon dioxide as soon as it is mixed with liquid. Unless you move quickly, the baking powder will lose its potency and your recipe won’t rise properly or at all.
Almost all commercially available baking powder now is called “double acting”. This means that the baking powder reacts both with liquid and the heat of the oven. This type of baking powder gives the baker a little more time without compromising the finished product. However, it is still best to get the recipe in the oven as quickly as possible.
The tartaric acid in the original baking powder has been replaced with two different acid salts; most commonly monocalcium phosphate and sodium aluminum sulphate. However, adding aluminum to baking soda is controversial. it is best thought to be avoided as a foodstuff and some people feel that recipes that use large amounts of baking powder, like biscuits, can have a metallic taste. Additionally, there are some who cannot tolerate any amount of sulphates. Many bakers also feel commercial baking powders don’t produce as delicate a product. You can find in some health-food and specialty stores aluminum-free (or non-alum) baking powder. However, it tends to be expensive and doesn’t keep well. But, many bakers prefer it.
Ms. Daley has a recipe for a make it yourself at home baking powder: for every teaspoon of baking powder called for in a recipe, combine 1/4 teaspoon baking soda, 1/2 teaspoon cream of tartar, and 1/2 teaspoon cornstarch. Blend well and use immediately. It loses potency with prolonged storage.
Baking powder, when stored properly, will last up to a year. Keep it in a cool, dry place. To test the potency of baking powder, place 1/2 teaspoon in a small amount of warm water. If it fizzes and bubbles away, it’s good.
Hope this helps. Happy baking!