Isolation And Purification Of Wheat Gluten Peptide And Its Antioxidant Activity

Wheat gluten is a byproduct of the wheat starch industry. The use in food is limited by its water-insoluble characteristic. The aim of the present study was to enzymatically hydrolyze wheat gluten for improving its solubility, upgrading functional properties and extending utilization. Based on previous study, dual-proteases were applied and its optimal parameters including the ratio of the two proteases, pH, and temperature were well investigated. A novel peptide was separated and purified from Wheat gluten hydrolate and its structure was characterized by Sephadex G 25 and DEAE-Sepharose FF. And antioxidant activity of the peptide was also well studied. Main results obtained were as followed:1). Firstly based on previous study, Neutrase was combined with different proteases including Trypsin, Papain, Alcalase; Special enzyme of hydrolyzed wheat protein and flavore proteinase to improve the hydrolysis degree and antioxidant activity of wheat gluten by assaying the activities of the DPPH radical scavenging and hydrolytic efficiency of hydrolysis.. Results showed that the combination of trypsin and neutral protease can efficiently hydrolyze wheat gluten. The optimal parameters was obtained as ratio of Trypsin to Neutrase 2:1, enzyme dosage 0.07 g, mass concentration of substrate 90 g/L, pH 9 and hydrolysis temperature 50℃by one-factor-at-a-time and Orthogonal test design. Under the optimum conditions, the DPPH radical scavenging activities reached to 92.87%.after 1.5h.hydrolysis.2). Secondly, the ultrafitration membranes with 10000 MWCO (Molecular Weight Cut off),5000 MWCO,3000 MWCO were applied to preliminarily isolate the peptides with different molecular from the hydrolysate of wheat gluten by Neutrase and Trypsin. Four peptide fractions were obtained and nominated as D-WG (original hydrolate),D-WG-10(≥10000 Da),D-WG-5 (5000～10000 Da),D-WG-3(3000～5000 Da) and D-WG-0 (≤3000 Da), respectively. The antioxidant activities of these peptide fractions were well investigated by assaying the activities of the DPPH radical scavenging, the reducing power, hydroxyl (-OH) radical scavenging and superoxide(O2-·) radical scavenging. Results showed that peptide fraction D-WG-0 demonstrated the most significant antioxidant activities. A novel peptide D-WG-0-Ⅰwas separated and purified by Sephadex G25 and DEAE Sepharose FF. The purity of D-WG-0-Ⅰwas determined as 84% with RT-HPLC.3). Finally, effect of D-WG-0-Ⅰon red blood cells (RBC) hemolysis, liver mitochondria swelling and the formation of malondialdehyde (MDA) in liver mitochondria was analyzed. Result indicated that D-WG-0-Ⅰcan effectively protect the biomembrane, reduce the hemolysis of red blood cells and lighten the damage of mitochondria, and demonstrated the most significant antioxidant activities. The antioxidant peptide D-WG-0-Ⅰwere identified to be Ser-Gly-Ala-Asp-Lys-Lys-pro-Ile-Lys-Ala-Asn-His by UV, IR and MALDI-TOF/TOF MS/MS.