09:46 – More kit work today. This time of year, the trick is to maintain sufficient finished goods inventory to allow us to ship in a timely manner, but not build up inventory so far that we end up with a lot of unsold kits in stock when the rush slacks off.
From some of the comments yesterday, I see that I need to write a brief explanation of chemical leavening agents. Baking soda (sodium bicarbonate, sodium hydrogen carbonate, or NaHCO3) is the basis of all common chemical leavening agents. In the presence of an acid or heat, baking soda evolves carbon dioxide gas, which forms the bubbles familiar to anyone who’s baked or made pancakes. In combination with a solid edible acid, baking soda becomes baking powder.
There are two types of baking powder, single-acting and double-acting. Single-acting baking powder contains a stoichiometric equivalent (or an excess) of the solid acid. When water is added to the dough, the baking soda and acid immediately react to form carbon dioxide bubbles. All of the baking soda is consumed in that process. Double-acting baking power contains an excess of baking soda. Part of that is consumed when water is added to the dough, forming bubbles, but part remains in the dough. When that remaining baking soda is exposed to heat in the oven, each two molecules of baking soda react to form one molecule of sodium carbonate, one molecule of water, and one molecule of carbon dioxide gas. That release of carbon dioxide because of oven heat is the second action of double-acting baking powder.
Almost any solid edible acid can be used to make baking powder. I mentioned citric acid because it’s as good as any other acid, it’s cheap (I paid about $2/pound for a five-pound bag of it), and as a very common food additive it’s very readily available in food-grade form. But you can use other solid edible acids such as cream of tartar, aluminum sulfates, and so on. The aluminum-based acids are popular in commercial baking powders, but concern about aluminum consumption has caused manufacturers to shift away from aluminum-based baking powders to those that use organic acids like cream of tartar or citric acid.
In fact, the acid doesn’t even have to be in powder form, which is why many recipes use only baking soda rather than baking powder. Liquid acids in the recipe–such as vinegar, sour cream, buttermilk, lemon juice, etc.–also react with baking soda to form carbon dioxide gas. If you use just enough baking soda to neutralize those liquid acids, you end up with the equivalent of single-acting baking powder, albeit partially liquid; if you use an excess of baking soda, you end up with the equivalent of double-acting baking powder.