Study On The Preparation Of Antioxidant Peptides From Enzymatic Hydrolysate Of Crab Waste

Hydrolysis conditions to prepare high antioxidant property hydrolysates were investigated and the antioxidant property stability of hydrolysates was studied in this paper. By using simulating gastrointestinal digestion method, changes in antioxidant property of hydrolysates in simulating gastric and intestinal fluids were also analyzed. The components with higher antioxidant property were separated and their molecular weights and amino acids compositions were measured. Results obtained can provide academic basis for the development and utilization of antioxidant peptides derived from crab meat. The main results were as follows:1. The effect of different proteases and various crab meat pre-treatment methods including heating, dehydrating, and dehydrating after defatting on antioxidant property of hydrolysate were studied. The results showed that the hydrolysate yielded by alkaline protease hydrolysis of crab meat defatted and dried had higher free radical scavenging rate. Using DPPH radical scavenging rate and superoxide anion scavenging rate as indices, optimum hydrolyzing conditions were obtained by response surface method.2. The antioxidant peptides in hydrolysate had strong heat-resistance, as its antioxidant property maintained in the range of over 93% at the temperature from 30℃ to 90℃. The antioxidant property of peptides increased with decreasing of pH and were maintained in acidity and neutral environment, but peptides lost antioxidant activity obviously in alkaline condition. DPPH free radical scavenging rate of hydrolysate with addition of Na Cl, sucrose, glucose, sodium benzoate, potassium sorbate, sodium glutamate decreased in different degree, but the hydrolysate still maintained over 94% activity.3. The antioxidant peptides had good digestion resistibility. In simulated gastrointestinal digestion experiment, Fe2+ chelating capability of hydrolysate decreased obviously, while scavenging rate of hydroxyl radical and superoxide anion maintained about 90%. Meantime, reducing power increased by 4.81% and 5.01% in simulated gastric and intestinal fluids respectively, while DPPH radical scavenging rate increased by 18.22% and 0.48%.4. Hydrolysate was separated through Sephadex G-100 gel filtration column and 12 fractions were obtained. Cavenging rate of hydroxyl radical, superoxide anion and DPPH radical, Fe2+ chelating capability, reducing power of various franctions were measured and compared. The result showed that fraction 4 and fraction 6 showed high active in antioxidation. Analyzed by gel filtration chromatography, molecular weight of fraction 4 was approximately 233 ~3771Da, mainly distributing in 1300 ~3700Da, and the molecular weight of fraction 6 was 318~4755Da, mainly distributing in 800~1800Da. By the analysis of amino acids, fraction 4 was rich in aspartic acid, glutamic acid, lysine and arginine with highest glutamic acid content of 20.17%. In fraction 6 amount of leucine was the highest, while the content of aspartic acid, glutamic acid, tyrosine, phenylalanine and arginine was also rather high.