On Food and Cooking

during mixing and react with the soda to
inflate an initial set of gas bubbles. Cream of
tartar, for example, releases two-thirds of its
leavening potential during two minutes of
mixing. If the acid is not very soluble, then it
will remain in crystal form for a characteristic
length of time, or until cooking raises the
temperature high enough to dissolve it — and
then it reacts with the soda to produce a
delayed burst of gas. There are several
different acids used in baking powders, each
with a different pattern of gas production (see
box, p. 533).
Most supermarket baking powders are
“double-acting”; that is, they inflate an initial
set of gas bubbles upon mixing the powder
into the batter, and then a second set during
the baking process. Baking powders for
restaurant and manufacturing production
contain slow-release acids so that leavening
power doesn’t dissipate while the batter sits
before being cooked.