to react with it. Common acid ingredients
include sourdough cultures, fermented milks
(buttermilk, yogurt), brown sugar and
molasses, chocolate, and cocoa (if not
dutched, p. 705), as well as fruit juices and
vinegar. A general rule of thumb: ½
teaspoon/2 gm baking soda is neutralized by 1
cup/240 ml of fermented milk, or 1
teaspoon/5ml of lemon juice or vinegar, or ¼
teaspoons/5 gm cream of tartar.
Baking Powders Baking powders are
complete leavening systems: they contain
both alkaline baking soda and an acid in the
form of solid crystals. (The active ingredients
are mixed with ground dry starch, which
prevents premature reactions in humid air by
absorbing moisture, and gives the powder
more bulk so that it’s easier to measure.)
When added to liquid ingredients, the baking
soda dissolves almost immediately. If the acid
is very soluble, it too will dissolve quickly