This invention is directed to an acid beverage composition, comprising; (A) a hydrated protein stabilizing agent; (B) at least one flavoring material comprising a fruit juice, a vegetable juice, citric acid, malic acid, tartaric acid, lactic acid, ascorbic acid, glucono delta lactone or phosphoric acid; and (C) a slurry of an aqueous protein material wherein the slurry of the aqueous protein material is prepared by a process, comprising; (1) preparing an aqueous extract from a protein containing material, (2) adjusting the pH of the aqueous extract to a value of from about 4 to about 5 to precipitate the protein material, (3) separating the precipitated protein material and forming a suspension of the precipitated protein material in water, (4) adjusting the pH of the suspension to a value of from about 4.0 to about 6.0 to form a slurry of an aqueous protein material, and optionally (5) pasteurizing the slurry of the aqueous protein material; wherein the acid beverage composition has a pH of from 3.0 to 4.5. Also disclosed are several processes for preparing an acid beverage composition.