Deamidation of food proteins by Bacillus circulans peptidoglutaminase was impaired by the large molecular size and unique conformation of these proteins. The limited ability of peptidoglutaminase to deamidate food proteins was increased dramatically by protein hydrolysis and altering protein conformation, principally by moist heat. A method to prepare enzymatically deamidated food proteins with a wide range of protein deamidation was developed. Enzymatic deamidation of proteins improved their functional properties especially in the mild acidic pH region (e.g., 4-6).