Malate, or malic acid, is a salt compound that is often used as a food preservative and, in nature, contributes to the sour flavor of apples and other fruit.In supplemental form, it is bound to citrulline and other various other supplements to give them stability in the body.alate, or malic acid, is a salt compound that is often used as a food preservative and, in nature, contributes to the sour flavor of apples and other fruit.