How to make (aluminum-free!) baking powder from scratch
A lot of people are nervous about a possible connection between aluminum / aluminium and Alzheimer's disease. While nothing about the connection has been conclusively proven as yet, there seems to be no harm in eliminating aluminum from places where it doesn't really need to be... like baking. (Except maybe in the baking pan or tin on the outside: and again, that should be your call.)
Many commercial double-acting baking powders in the US contain small amounts of aluminum. (The "double action" comes from the addition of sodium aluminum sulfate, which causes the powder to react more slowly to heat, as in the oven.) With this in mind, why not try making your own baking powder at home, from scratch? This home-made single-acting baking powder won't behave much differently in your baking than the double-acting type does.
Additionally, homemade baking powder gets around one of the main problems with the storebought stuff: it stops working over time. When you make your own from scratch, in small batches, you know it's going to work right every time.
The method is simple. To make the one teaspoon of commercial baking powder, mix together:
- 1/2 teaspoon cream of tartar
- 1/4 teaspoon baking soda
- 1/4 teaspoon cornstarch (cornflour, for UK bakers)
That's all there is to it. To make larger quantities, just increase the amounts in proportion.
Please note that there are also aluminum-free commercial baking powders on the market: one of them (in North America) is Rumford. Check the labels of your local brands to see what secondary raising agents they add.
(By the way, here's a way to test whether your baking powder is still good: Boil half a cup of water and add half a teaspoon of the baking powder to it. If it fizzes and froths up energetically, it's fine. If it doesn't react, or reacts weakly, get rid of it: it's no good and your baking will come out flat.)