(Thanks to readers KayeC, Pickles, Melinda, Susan K., Shirley, and Heather for their help in tracking down information for this post)
Baking powder: an ingredient that is so helpful to gluten-free baking and yet one that is often misunderstood. I thought I would do a post to help answer the questions I’ve been getting about it.
There are two main issues with baking powder that need clarification. One is the difference between single acting and double acting baking powder and the other is the fact that some baking powders include wheat starch as ingredient.
Baking powder, as you probably know, is what is called a “leavener” in baking. Further, it is a chemical leavener, to distinguish it from yeast or steam as leaveners. A leavener, as you might guess, is something that leavens—or raises—baked goods. Without leaveners, baked goods would be flat and hard—because they would have no air holes. Leaveners create the gas or steam that works on air pockets in baked goods during the baking (and rising ) process to lighten them.
Many gluten-free baked goods need a little (or a lot) of extra leavener because the gluten-replacer isn’t as elastic as gluten. And double-acting baking powder is an important leavener when baking cakes, muffins, and even breads because it has a lot of strength.
Baking powder is not the same as baking soda—but it contains baking soda. Baking soda, also known as bicarbonate of soda, is an “alkaline” leavening agent. If you remember your high school chemistry, you might remember that alkaline is the opposite of acid. Baking soda needs acid to create the chemical reaction that causes it to bubble. Remember school experiments where you mixed baking soda with vinegar (an acid) to create a bubbling mess that could be used as “lava” on a model of a volcano? The combination of the baking soda and the acid in the vinegar releases carbon dioxide that causes the bubbling. And it is this bubbling that causes baked goods to rise.
Therefore, baking soda is used in baked goods that have some sort of acidic ingredient, such as: buttermilk, vinegar, brown sugar, molasses, honey, maple syrup, citrus, or chocolate (not Dutch process). It needs the acid in these ingredients to start the bubbling, gas-releasing process that raises the baked item. Please note that Dutch process cocoa has had the acidity neutralized.
But, there are many baked items that do not contain an acidic ingredient and in which baking soda won’t work. That’s where baking powder comes in. Originally, baking powder was a combination of baking soda plus an acid. In fact, most recipes for homemade baking powder contain baking soda mixed with cream of tartar for the acid. This solves the problem of a recipe not containing an acid for the baking soda to work on—baking powder includes both items in one neat package. This type of baking powder is called “single acting”—it contains one acid for the baking soda to work on.
In commercial forms of baking powder, a starch is also included to protect against premature reactions caused by humid storage conditions. The added starch is something that can cause problems for gluten-free bakers. Years ago, the most commonly added starch was wheat starch—making baking powder not gluten-free. Nowadays, in the United States, the most common starch added is cornstarch (and sometimes potato starch). This means that most baking powders in the U.S. are gluten-free (contrary to a lot of misinformation out there that is based on old research). However, in the UK, there are still several baking powders that contain wheat starch. Bleh. This is why you always need to read labels and ask questions.
Single acting baking powder was a good beginning because it created a leavener that works on any type of baked good, regardless of whether or not it contains an acid. But, once it is mixed with the wet ingredients and the baking soda and the acid mixes together, the chemical reaction starts. Therefore, the item to be baked has to go into the oven right away, before the bubbling action stops. This led to another baking powder innovation—“double-acting” baking powder. Double-acting baking powders contain a second “high heat” acid that works more slowly and that is heat-activated. This gives the baked item two leavening actions—one that creates a rise during the mixing process and one that creates a rise during the baking process.
This extra leavening power is what makes double-acting baking powder so important and helpful for gluten-free cakes, muffins, and breads (it’s not needed for cookies, which are usually fairly flat). Therefore, I always advise folks to add a truly double-acting baking powder to their gluten-free baked items if they are finding that things are baking up flatter instead of fluffy. The amount needed is a matter of trial and error for each type of recipe.
Note (added 11/12/12): single acting baking powder is often just fine for most baking. It depends on the thing you are baking. Don’t give up on baking just because you can’t find or can’t use commercial double-acting baking powder. I always say try it and see what happens. My husband often accidentally gets me a single-acting baking powder when he goes shopping and it is often just fine.
Unfortunately, some baking powders aren’t really double-acting, even though they claim to be. These baking powders still only have one acid—and therefore they do not really work by being activated by heat. As far as I can tell, there aren’t any laws guiding the labeling of baking powders in the US. This causes bakers to wonder what the heck happened to the fluffy factor of their cakes and muffins. To be truly double-acting in the way we need them to be double-acting, a baking powder needs to contain 2 acids. And, before you ask: I don’t know of any way to make double-acting baking powder at home. Some recipes claim to be double-acting, but they just seem to add extra cream of tartar.
Therefore, it is important to read the labels. You need to see that the baking powder you’re using has two acids, as well as the leavening agent, and a starch. This means that a truly double-acting baking powder has four ingredients instead of the three that single-acting baking powders have.
Unfortunately, there is a further issue with many kinds of double-acting baking powder. The second acid that is often added to double-acting baking powders is sodium aluminum sulfate (SAS). The problem with SAS (in addition to it being aluminum) is that it has a distinctive and bitter metallic taste that is unpleasant to many people. You may notice it in your favorite baking powder biscuits or scones. And this taste is especially noticeable in gluten-free baking where more baking powder is often needed.
Therefore, if you want to avoid this unpleasant taste, you should get a double-acting baking powder that is labeled “Aluminum-free” (or that does not have SAS on the label). As far as I know, as of this writing there are only two double-acting baking powders in the U.S. that are labeled gluten-free, are truly double-acting, and are aluminum-free: Bob’s Red Mill and Argo.
Two others, Watkins and Barry Farm baking powders are double-acting and are aluminum free, but don’t seem to be labeled gluten-free. For what it’s worth, I don’t see any gluten-containing ingredients on their labels (which means there might be cross-contamination issues).
Added 11/12/12: Another issue with baking powder is the potential presence of GMO ingredients. Since most commercial baking powders contain cornstarch as the starch, there is a good chance that the corn used is GMO corn (most non-organic corn in the U.S. is GMO corn. That’s scary). If this is of concern to you (as it is to me), I recommend that you look for baking powders that list “organic” cornstarch or “non-GMO” cornstarch. This will ensure that you are not getting GMO cornstarch. Apparently Rumford is now doing a GMO-free baking powder–look for the GMO-free label on the jars.
Please make a note of the expiration date on your baking powder container. Your baking powder will stay good indefinitely in an unopened container. But, it will start to degrade once the container is opened. This is because every time you open the container, the moisture from the air in your kitchen gets in and causes a little reaction. Eventually, this causes the ingredients to lose their power. So, you need to be sure that you’re using your baking powder before its expiration date.
Below is the status of baking powders available in the United States, the UK and Europe (as of 11/9/12). This list is to be used as a guide, not as a definitive word. Please read labels before you use anything, as ingredients can change. And note that if it is not expressly labeled “gluten-free,” you can’t be assured that the product is not cross contaminated with gluten. D/S refers to Double/Single-Acting.
|*||Bob’s Red Mill||D||corn||yes|
|*||Clabber Girl (Davis in UK)||D||corn||no|
|*||Rumford (owned by Clabber Girl)||S||corn||yes|
|*||Dove’s Farm (UK)||S||corn||yes|
|*||Herbs Gardens+Health (UK)||?||wheat||?|
Let me know if you find out information that differs from the info I have here! Thanks!