Abstract:Proteins in the by-products of Grifola frondosa polysaccharides extraction were isolated and their functional properties were studied. Proteins in the supernatant obtained after ethanol precipitation of Grifola frondosa polysaccharide extract were isolated by ultrafiltration membrane with a molecular weight cut-off of 5.0 ku. Polypeptides were obtained by enzymolysis and secondary ultrafiltration of the isolated protein. Functional properties of the polypeptides and proteins, including solubility, foaming capacity, and antioxidant activities,were analyzed and compared. The results indicated that ultrafiltration could effectively isolate and purify the protein, with a purity of 70.24% and a yield of 7.26%. The isolated protein was found to be a high-quality edible protein, with essential amino acids/total amino acids (EAA/TAA) and nonessential amino acids/total amino acids (EAA/NEAA) values of 40.5% and 68.0%, respectively. The solubility and antioxidant activities of the isolated protein were significantly increased after enzymolysis by each enzyme tested. Of these enzymes, papain yielded the highest degree of hydrolysis (DH = 8.94%). The polypeptide showed relatively good antioxidant activities, with scavenging rates for hydroxyl radical (?OH), 2,2-diphenyl-1-picrylhydrazyl (DPPH?), and [2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)] (ABTS)? + free radical, of 66.14%, 65.78%, and 98.95%, respectively, while those of the isolated protein were 50.88%, 44.01%, and 72.74%, respectively.
