Investigations of Enzymolysis Technology and Antioxidant Activity of Goa'ts Milk Casein

In order to prepare highly active peptides derived from goa t's milk casein (GMC), the enzymolysis technology for GMC with neutral protease, trypsin, papain or alkaline protease was optimized using orthogonal array design. Based on this, these enzymes were combined pairwise for achieving a maximum amino nitrogen content in GMC hydrolyaste. Meanwhile, the antioxidant activity of GMC hydrolyastes prepared via single enzyme or double enzyme hydrolysis was also evaluated by DPPH radical scavenging assay. Results showed that a content of total peptide substances of 8.5379 mmol/g was exhibited in GMC. For single enzyme hydrolysis, neutral protease and trypsin could hydrolyze GMC with higher degree of hydrolysis when compared to alkaline protease; for double enzyme hydrolysis, the combination of trypsin with neutral protease or alkaline protease exhibited higher degree of hydrolysis than other combinations, and the corresponding values of degree of hydrolysis, average peptide chain length and average relative molecular weights were 17.34%, 5.77 and 692 for neutral protease + trypsin and 16.40%, 6.10 and 732 for trypsin + alkaline protease, respectively. Additionally, neutral protease and trypsin + alkaline protease hydrolysates of GMC displayed stronger DPPH radical scavenging activity than other hydrolysates.