I have no baking powder, but I do have baking soda and powdered citric acid. Can these be combined to substitute for 1 teaspoon of baking powder? If so, how much of each would I use?
Yes, I have found several sources that say that citric acid is about 4 times the strength of cream of tartar. So, mix 1 teaspoon of baking soda and 1/2 teaspoon of citric acid and use a 1/2 teaspoon of the mixture.
That should work. Let us know!
EDIT: Oops, I should have mentioned this before the OP accepted. Hopefully, he'll realize, or see this. That substitution will approximate single action baking powder, so don't dilly-dally before cooking! (Difference Between Double and Single Action Baking Powder)
2nd EDIT: Just to be extra confident, I compared the reaction (according to the method of David Lebovitz) of 1/4 tsp of my recommended mixture with boiling water and 1/2 tsp of new Rumford Baking Powder with boiling water. The results seemed identical.
3rd EDIT: I actually found this question pretty intriguing. While I could find plenty of evidence that it should work (including my own little water experiment), I couldn't find anything definitive that said it does work.
Well, it just so happens that I had some cream in the fridge, and I have been meaning to try America's Test Kitchen's cream biscuits. With nothing in them but flour, sugar, baking powder, salt and cream; they should be perfect for comparing real baking powder with the substitution.
I made biscuits.
They taste as identical as they look. (pretty yummy too)
I can now say with authority, the substitution works. 1 tsp fresh Rumford Brand Baking Powder = 1/2 tsp of a mixture of 1 tsp baking soda and 1/2 tsp citric acid.
From separate containers of baking soda and citric acid, add baking soda at 1/3 the amount of baking powder required then citric acid at 1/2 of the amount of baking soda already added.
This is quantitatively the same as above but avoids the reactivity problems of pre mixing baking soda with citric acid.
I use the substitution because I prefer to avoid the aluminum that is in baking powder. As already mentioned, just start baking immediately after mixing in this substitution since it is single action versus the double action of baking powder. It always works for me.