Sodium aluminum phosphate, or SAIP, is a group of inorganic compounds that are formed from aluminum phosphates and sodium salts. It is mostly found in food products. These compounds can be either acid or basic, depending on their specific chemical composition.
Acidic sodium aluminum phosphate is most commonly used as a leavening agent for baking, but is also used as an emulsifier in processed cheese. Most baking applications use a mixture consisting of 70 percent SAIP combined with 30 percent sodium bicarbonate, or baking soda. When mixed with water, these compounds react to produce carbon dioxide, which helps baked goods rise. However, unlike pure baking soda, most of the SAIP reaction doesn't occur until the batter has been heated in an oven.