Glutaminase‐induced deamidation and hydrolysis of casein and metal‐chelating or ACE‐inhibitory activity of the hydrolysates in vitro

Summary Glutaminase (EC 3.5.1.2) was applied in this work to induce deamidation and hydrolysis of casein. Some reaction conditions based on casein deamidation were studied. Three casein hydrolysates with degree of deamidation of 2.8%, 5.8% and 8.5%, or degree of hydrolysis of 2.5%, 3.4% and 4.9%, respectively, were prepared at casein concentration 5% (w/v), glutaminase addition level 400 U kg−1 casein, reaction temperature 37 °C and reaction times 6, 12 and 24 h, respectively. Evaluation results showed that when iron (II) was added at 60 μm, iron (II)‐chelating powers of three hydrolysates were 41.1, 45.4 and 55.3%, while that of original casein and EDTA were 36.1 and 13.6%. Calcium (II)‐chelating power of three hydrolysates was 1.23, 1.41 and 1.49 mmol g−1 casein, whereas that of original casein was 1.05 mmol g−1 casein. Three hydrolysates also had ACE‐inhibitory activity in vitro, with IC50 values from 0.75 to 2.34 mg mL−1.