Friday, January 10, 2014

Baking soda, baking powder, and "the Baking Powder Controversy"

It's not every girl who runs around telling you about the Baking Powder Controversy of 1900. Herewith, a look at my past life as Chicago Baking Examiner. (I have imprew-ved this one.) If any chemist wants to just glance over and correct what follows, I would be obliged to him. 

Baking soda or bicarbonate of soda has long been used to quickly leaven cake batter and cookie dough. It was first factory produced in the 1840s. Baking soda must have an acid to work with, so as to produce the carbon dioxide gas bubbles which raise and stretch a dough. This is why any cake or cookie recipe (often an old one) calling for just baking soda will also require a liquid acid like orange juice, vinegar, or lemon juice, or a dry acid like cream of tartar (potassium acid tartrate).

Cream of tartar, as luck would have it, is derived from winemaking. Grapes are the only important natural source of tartaric acid, which precipitates out of wine in the barrel (as "tartrates") and is then collected and mixed with potassium hydroxide to create a usable salt. This cream of tartar, also first marketed in the 19th century, proved another boon in the kitchen. Using it gave home bakers a dry, stable acid to combine with their baking soda, easily measured and in no danger of spoiling like a lemon or an orange. The combination of 2 parts cream of tartar to 1 part baking soda makes what the cooks of yesteryear would have called a "single acting baking powder," meaning that it begins to do its work as soon as a batter is moistened.

It didn't take long for 19th century grocers to go the home cook one better and offer pre-mixed baking soda-and-cream of tartar powders, single-acting of course. But sometimes the packaged powders were composed of other acidic chemicals like alum or phosphate along with the soda. This is why antique advertisements will sometimes reassure us that a certain "perfectly pure and wholesome" baking powder is a "pure cream of tartar powder." Alum and phosphate -- "harmful and rascally adulterations" -- did not leaven as well as cream of tartar, and they left behind a poisonous "residuum" in the baked good which rendered it, according to the cream of tartar powder producers, "positively unsafe for human food." You can read court testimony here about the Baking Powder Controversy, circa 1900. I am not quite heroic enough to plow through all the fine print, but the Controversy seems to have involved legislation at the state level -- in Missouri, for one -- decreeing that only cream of tartar could be used in baking powders, followed by bribes and bribery trials because the alum-and-phosphate people wanted to get the cream-of-tartar people called unfair monopolists. A glance back into these records will also show that, a hundred years ago, Missouri state officials were still named after Robert E. Lee ....

The alum-and-phosphate magnates lost, which surely was a good thing;  I think I would rather have my leavening agents derived from nice grapes rather than from, well, alum and phosphate. Anyway when, also in the 19th century, plain corn starch was added to prefab single-acting baking powder to help keep it dry, it could then raise batters twice: first, upon moistening, and then when the dough was put into the oven and the chemicals reacted to heat. This accounts for today's perfectly pure and wholesome baking powders still mysteriously announcing on every can, evidently for the benefit of ghostly Victorian bakers who would have understood the point, that they are "double acting."

As for the great question, "can you substitute?" The interlocking chemical reactions among baking soda, cream of tartar, and the baking powder they make, means that substituting one for the other requires a moment's thought. And sometimes it can't be done. To wit:
  • baking soda, alone, needs an acid to work with and can't replace baking powder
  • you can make your own baking powder by mixing 2 parts cream of tartar with 1 part baking soda. It will start reacting instantly to moisture and won't work further when heated, which is why some recipes instruct you to put the batter into the oven as speedily as possible
  • baking powder can replace baking soda, since it is pre-mixed of both necessary chemicals, but you will need quite a bit more -- maybe quadruple the amount -- and it may change the taste of your product.

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