Deamidation of Protein in a Soy Extract by Ion Exchange Resin Catalysis

Proteins in a soy extract were partially deamidated in dilute HCl (0.05N) with and without the use of Dowex 50 resin as a catalyst. In the presence of Dowex 50 resin, soy protein underwent about 1.5 to 3.0 times as much deamidation, depending on temperature, as did protein in the absence of resin. Increasing the temperature from 58° to 85°C increased both deamidation and peptide bond hydrolysis. The ratio of deamidation to total hydrolysis (the sum of deamidation and peptide bond hydrolysis) decreased as temperature increased. This ratio was higher for the catalyzed reaction. The deamidated protein showed improvement in various functional properties including solubility, water‐binding, whippability, and the ability to emulsify oil.