Baking Powder

baking powder a raising agent used in breads, cakes, and biscuits. It consists of a mild acid and a mild alkali which react together when wetted, generating carbon dioxide which forms bubbles in the dough. The reaction begins at once, so there is no need to leave the dough to ‘ripen’ as when using yeast.

The alkaline component of baking powder is usually bicarbonate of soda, also known as sodium bicarbonate (NaHCO₃) and as baking soda. The first type, invented in the USA in 1790, was ‘pearl ash’, potassium carbonate prepared from wood ash. This provided only the alkali; the acid had to come from some other ingredient, for example sour milk. Pearl ash reacted with fats in the food, forming soap which gave an unpleasant taste. Soon it was replaced by bicarbonate of soda, which still reacts in this way but to a much smaller extent. An American name used for either of these alkali-only agents was saleratus.