γ-Glutamylation of Soybean Meal Enzyme Hydrolysate and Taste and Anti-Inflammatory Activity of Its Products
γ-Glutamyl peptide was found to be a kokumi peptide with various functional properties.Soybean meal was used as the raw material to investigate the effects of flavour protease andγ-glutamylation on the taste characteristics and anti-inflammatory functional activities under conditions of synergistic enzyme digestion.The enzyme digest was obtained under the conditions of flavour protease digestion for 9 h,enzyme digestion temperature of 55 ℃,enzyme dosage of 0.75％,and pH 7.0,and then γ-glutamylation modification was carried out by the enzyme dosage of 2.00％,pH 10.0,enzyme digestion temperature of 35 ℃,and enzyme digestion time of 3 h.The resulting product was the crude soybean glutamyl peptides,which showed significant improvement in taste,especially in terms of saltiness,umami,and kokumi.It was demonstrated that after modification by γ-glutamylation,soybean meal had potential anti-inflammatory activity in addition to improving taste characteristics.Enzyme-linked immunosorbent assay was used to detect the expression levels of IL-8 and TNF-α in the experimental group.The results showed that the expression levels of inflammatory factors TNF-α and IL-8 were down-regulated by about 22％and 15％,respectively,after pre-treatmented with 10 mg/mL of soybean glutamyl peptide crude products,which were close to those in the normal group,and had significant difference with those in the positive control group(P＜0.05).Combined with the results of substance changes,it could be speculated that the enzymatic reaction degraded the large-molecule proteins(greater than 10 kDa)in soybean meal into small-molecule peptides,and the molecular weights mainly less than 1 kDa.After γ-glutamylation reaction,some of the amino acids were converted into γ-glutamyl peptides,and the total free amino acid content of soybean meal was reduced from(150.24±0.04)mg/g to(128.49±0.04)mg/g,and the yield of γ-glutamate dipeptide was predicted to be about 32.24 mg/g.This study provided a theoretical basis for the functional processing and product optimisation of soybean meal-derived condiments.
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