The Use Of Ultrasound For Enzymatic Preparation Of Antioxidant Peptdes From Wheat Gluten

Wheat gluten was hydrolyzed by Alcalase 2.4L under ultrasound. Different antioxidant assays in vitro were employed to evaluate the antioxidant activities of the wheat gluten hydrolysate (WGH) obtained. The best ultrasonic parameters were the maximum ultrasonic power (400w) and low-frequency (25kHz) under the conditions of hydrolysis 30min. Under optimal conditions (temperature 50℃, pH9.0), WGHL (WGH which was obtained by low frequency ultrasound) exhibited the strongest antioxidant activities, with an IC50 value of 0.513mg/mL for ferrous iron-chelating activity, as well as a high and dose-dependent reducing power. In the linoleic acid system, a longer induction time indicated a significant decrease of lipid peroxidation. In addition, WGH also exhibited notable ABTS radical scavenging activity.Then, the results of ultrafiltration showed that WGHU-5 (WGH with the molecular weight below 5kDa) possessed the highest antioxidant activity. When the concentration of 0.2-0.4 mg/mL, the ferrous ion chelating activity of WGHU-5 was twice as much as WGH. The oxidation of linoleic acid was significantly inhibited by the addition of WGH (P<0.05) after 36h than WGH. When the concentration of 4mg/mL, TEAC value reached 1.45mmol/L Trolox. And the high-performance liquid chromatography analysis of its molecular weight revealed that the fractions below 2kDa accounted for the majority. It can be conjectured that antioxidant peptides fractions were concentrated in 2kDa. In order to investigate the effect of WGH and WGHU-5 on D-galactose induced aging model mice. The mouse were divided into normal control group, D-galactose model group, WGH low dose group, WGH high dose group, WGHU-5 low dose group and WGHU-5 high dose group. The results show that high-dose group WGHU-5 can significantly improve SOD, T-AOC, GSH- PX activity (P<0.01) of plasma, heart, brain, liver and kidney tissue, but reduce the MDA (MDA) content. It indicated that wheat gluten hydrolysates had obvious antioxidant effect.In order to get better quality products, the antioxidant peptide was fractionated by ethanol elution from a macroporous adsorption resin (DA201-C). It was found that adsorption reach equilibrium in 30min, and static desorption rate can reach 70% in 30min using the basic 75% ethanol. WGH can be well separated by using gradient elution ethanol. The basic inorganic salt ions are washed out at the end of elution. The antioxidant capacity of each component increased with the hydrophobicity and then decreased. 75% ethanol fractions exhibited the highest antioxidant activity, at a concentration of 0.4mg/mL, the ferrous ion chelating activity was 84.13%, TEAC value of 0.36mmol/L Trolox,and desalination rate reached 93.56%.The fraction was then identified by MALDI-TOF-TOF MS/MS. Their molecular weights were 951Da and 1349Da respectively. The amino acid sequences were Ser-Arg-Tyr-Asp-Ala-Ile-Arg-Ala(SRYDAIRA) and Tyr-Pro-Leu-Glu-Ala-Ala-Gly-Asp-Thr-Lys- Arg-Glu(YPLEAAGDTKRE).