Study On The Preparation Of Antioxidant Peptides From Defatted Hazelnut Meal

Antioxidants properly replenished can reduce the functional damage from free radicals.Synthetic antioxidants are confirmed of being responsible for liver damage and carcinogenesis in laboratory animals.Natural antioxidants has been concerned,since they are safer and better antioxidant activity than synthetic compounds and can be used in the functional foods.This experiment mainly study hazel meal antioxidant peptides in order to solve the probllem of hazel utilization and product nature antioxiadant peptides.With hazelnut meal left after oil extraction as material,acid precipitation process was adopted to prepare hazelnut protein isolate.Based on one-factor-at-a-time experiments,response surface methodology was used to optimize process conditions for maximizing total protein extraction of defatted hazelnut meal.The result revealed that the optimal preparation conditons were as follows:alkali extraction time 58 min?alkali extraction pH 8.5?alkali extraction temperature 47?,solid liquid ratio1:26,acid precipitation pH 4.5,under the optimal conditions the extraction rate of defatted hazelnut meal protein was about 19.31%.There are three Proteases such as alkaline protease,neutral protease,papain protease hydrolyzing protein of defatted hazelnut meal.Researching the degree of hydrolysis,DPPH free redical scavenging activity and the composition of amion acid from compound enzymatic hydrolysates.Protease screening was employed to prepare antioxidant peptide released from defatted hazelnut meal with enzymolysis method.Changes in DPPH free redical scavenging activity and amion acid composition of antioxidant peptide released from defatted hazelnut meal before and after in vitro digestion were investigated.The results indicated that neutral protease was screened out from the following three kinds of protease.The optimum hydrolysis conditions obtained from the experiments were as the following:hydrolysis temperature of 43.7?,enzyme dosage 17000 U/g,hydrolysis time 1.7h,the degree of hydrolysis 11.57%,DPPH free redical scavenging activity 80.38%,the content of amino acid in neutral protease hydrolysates 46.07 g/100g.ED₅₀ of scavenging DPPH free redical apparently decreased by 3.27 mg/mL and the composition of total amion acid decreased by 7.584 g/100g after in vitro digestion.The hydrolysate from halnut meal protein was prepared by neutral protease.Halnut meal antioxidant peptides were separated by ultraflitration and gel filtration chromatography?Sephadex G-10?,the fractions were evaluated for their antioxidant activity by DPPH free redical scavenging activity.The frations P2 with high antioxidant activity were examined by Liquid charomatography-mass spectrometry?LC-MS-MS?.Seven novel peptides with weight of 362 Da,475 Da,588 Da,662 Da,701 Da,327 Da and 279 Da were identified as His-ILe/Leu-Pro,ILe/Leu-Val-Asp,Thr-Pro-Pro-His-Lys,His-ILe/Leu-His-Ser-Ala-Thr,Cys-His-Ser-ILe/Leu-Met-ILe/Leu,Thr-His-Ala and Phe-ILe/Leu.The conclysion is that hydrophobic Amino acids and aromatic Amino acids can improve antioxidant activity of halnut meal antioxidant peptides.