Optimization of Enzymatic Hydrolysis Conditions for Preparation of Functional Oligopeptide from Silkworm Pupa Protein

In order to optimize the production process of functional polypeptides from silkworm pupa protein by enzymatic hydrolysis,the effects of different proteases,temperature,pH,substrate concentration and enzyme amount on the degree of hydrolysis(DH) and the trichloroacetic acid nitrogen solubility index(TCA-NSI) were explored using response surface methodology.It was proved that trypsinase,flavourzyme and neutral protease were the most effective enzymes for the hydrolysis of silkworm pupa protein.The optimal conditions were found to be hydrolysis temperature of 54.6℃,pH 7.38,substrate concentration of 7.33%,protease dosage of 3.62% and hydrolysis time of 6 h.Under these optimized conditions,DH of 29.2 and TCA-NSI of 81.14% were obtained.In the obtained functional polypeptides,the content of peptide reached 74.6%,with a number average molecular weight of 665.5 Da and a weight average molecular weight of 726.9 Da,while the content of free amino acid was only 7.33%,which indicated that the low molecular peptide instead of free amino acids was the main ingredient,although the silkworm pupa protein was enzymatic hydrolysis by depth.