Abstract: A hydrolyzed proteinaceous milk solid is prepared from a heat treated skim milk liquor which contains denatured whey proteins as well as casein proteins. The solid is prepared by rapidly heating the skim milk liquor to a temperature above 170.degree. F. and adding acid to the heated skim milk liquor to adjust the pH of the liquor to a pH of about 4.7. The heated pH adjusted liquor is aged for a time period during which coagulation and agglomeration of whey and casein proteins, carbohydrates and ash takes place forming a plurality of coagulum suspended in the remaining whey liquid. The coagula is separated from the whey liquid, cooled, dewatered and dried. The resulting dry solid is treated with a caustic agent as, for instance, sodium hydroxide, in a solid phase reaction to yield the hydrolyzed proteinaceous milk solid.