Sodium Acid Phosphate
Disodium pyrophosphate or sodium acid pyrophosphate is a buffering and chelating agent, with many food and industrial uses. It is polyvalent, and acts as a Lewis base, so is effective at binding polyvalent cations. Sodium acid pyrophosphate is a GRAS substance for food use. It is used in canned seafood to maintain color and reduce purge during retorting. It is an acid source for reaction with baking soda to leaven baked goods. In cured meats, it speeds the conversion of sodium nitrite to NO2- by forming the HONO intermediate, and can improve water holding capacity. Disodium pyrophosphate also is found in frozen hash browns and other potato products, where it is used to keep the color of the potatoes from darkening.