| There were a lot of pumpkin resource in Heilongjiang where was main areas of origin of seed squash,pumpkin seed oil was considered to have health function and more exploitation by people, skim pumpkin seed meal as high quality protein was used for deeply research and development. Fat and meal of germination pumpkin seed was much functional and studied as a new direction. In this study, take skim sprouted pumpkin seed meal as the main raw material, extracted protein in pumpkin seed with the method of alkali-extraction and acid-precipitation. antioxidant peptide produce was obtained by a fractional hydrolysis with alkaline protease and caroid and antioxidant activity were evaluated. Higher action antioxidant produce was obtained by separation and purification. The main study content and fruit were listed as follows:(1)In this study, germination pumpkin seed protein isolate was extracted by using the method of alkali-extraction and acid-precipitation. By result of central composite rotation test and response surface analysis, protein extraction rate of the three factors of primary and secondary order is liquid ratio, extraction temperature, extraction pH. Optimum conditions for the extraction temperature 40.4℃, liquid ratio is 30:1, pH 10.4, the theoretical value of extraction rate of protein was 78.52% under these conditions, but the actual extraction rate of protein was 78.4% (n=3), protein purity was 83.42%.(2)Screening enzyme by examining degree of hydrolysis and reducing power, alkaline protease and papain enzymes is the best protein enzymes on hydrolysis of pumpkin seeds, so alkaline protease and papain enzymes were selected for obtaining pumpkin seeds sprout oxidized peptide by this two-step enzymatic hydrolysis. By quadratic regression rotation design and a comprehensive measure of two indicators,determine optimum conditions of the alkaline protease the one step of the two-step enzymatic hydrolysis: substrate concentration 5%, reaction temperature 58.5℃, enzyme dosage 7133 U/g, hydrolyzate pH 9.54, then reducing power was 1.338(n=3). Under these conditions, after alkaline protease hydrolyzed to inactivate enzyme, then started the second step hydrolysis test. By central composite rotation test, the second step papain enzyme optimum conditions were determined: enzyme dosage 4084 U/g, reaction temperature 52.3℃, hydrolyzate pH 6.53. Under these conditions, the reducing power was 1.531(n=3). After the second hydrolysis, the reducing power was increased 14.42% than the first step hydrolysis.(3)The test determined the antioxidant activity of polypeptide pumpkin seed sprout. Reducing power and free radical scavenging ability of polypeptide pumpkin seed sprouts are increased with the polypeptide concentration increased, in a certain range of dose relationship. When the peptide concentration was 20 mg/mL, the reducing power was 0.841, little higher then BHA(0.001%), which OD was 0.835; when the peptide concentration was 30 mg/mL, the reducing power was 1.097, higher then the reducing power of 0.2 mg/mL VC(0.945); the IC50 of the pumpkin seed sprout antioxidant peptide to eliminate super oxygen anion free-radicals, scavenging capacity to hydroxyl free radical and DPPH free radical were 6.36 mg/mL, 6.55 mg/mL and 5.42 mg/mL.(4)The test selected desalination macroporous resin for desalination, desalination rate was 92.37%, polypeptide of the maximum rate was 90.26%. Peptide concentration was 10 mg/mL after desalination, the reducing power raised 12.13%; the IC50 of the pumpkin seed sprout antioxidant peptide after desalination to eliminate super oxygen anion free-radicals, scavenging capacity to hydroxyl free radical and DPPH free radical reduced 10.82%, 14.96% and 8.3%.
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