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Enzymatic hydrolysis is the most commonly used method to reduce the antigenicity of milk protein, but free protease is unstable and difficult to recycle after application. In this study, alcalase and neutrase were selected for immobilization on the modified magnetic Fe 3 O 4 nanoparticles. The reusability of the immobilized enzyme was 68.23% of the total starting activity after 5 recycling batches. The optimal hydrolysis conditions were an enzyme to substrate ratio of 6000 U/g and reaction at 50°C and pH 8.5 for 3 h. Under these conditions, 22.76% hydrolysis of hydrolysate was achieved, and the antigenicity reduction rates of β-lactoglobulin and casein were 21.34% and 30.89%, respectively. In addition, 82.75% of the hydrolysate had a molecular weight less than 1 kDa, and free amino acids represented 13.65% of the sample. This result showed that the hydrolysis with immobilized enzyme was similar to that with free enzyme and the immobilized enzyme could be applied to produce hypoallergenic hydrolysate.

In this study, we prepared a cold-set whey protein emulsion gel that was mediated by citric acid and a pre-emulsification method. A pre-emulsified solution was prepared with thermally denatured whey protein and butter. The stability and rheological properties of the emulsion gel were examined. The results demonstrated that the system changed from liquid behaviour at low protein contents to emulsion gel behaviour at high protein contents. Moreover, this method could produce a stable emulsion gel and its properties could be modulated by altering the protein and fat contents.