| The antioxidant peptides of peanut protein isolate are a group of active peptides gotten from peanut proteins by controlled hydrolysis and refinement. By far, antioxidant ability of peanut peptide is the basis of physiological functions, such as bioactivity on antioxidant ability, blood pressure reducing activity, cholesterol and blood sugar reducing activity, anti-fatigue activity and so on. In addition to providing the human body an effective amino acids, peanut peptide and peanut protein has the same process characteristic certainly and physiology activity. It is one of the most important aspects that peanut is further developed by peanut protein hydrolyzed.The follo wings are the experiment results:By using the mono-factor experiments, Box-Behnken experimental design involving the above3factors at3levels was employed, and effects of ultrasonic power, time and temperature on the technology, in which DPPH free radicals scavenging activity was taken as response value, were analyzed with response surface methodology. The optimum pretreatment conditions were as follows:ultrasound power400W, pretreatment time25min, and pretreatment temperature61℃. Under such conditions, the predicted value of DH and DPPH free radicals scavenging activity respectively was25.306%,78.81%. The conditions obtained by response surface methodology were believable.Peanut protein prepared by ultrasound pretreatment was sequentially hydrolyzed with two enzymes. The optimal hydrolysis mode of peanut protein was selected from hydrolysis with pairwise combination of alkaline protease and trypsin that resulted in higher degree of hydrolysis and DPPH free radicals scavenging activity than papaya protease, neutral protease and pepsin, or each of them. The combined ratio of alcalase and trypsin was determined by test, and the hydrolysis parameters of multi-enzyme and Flavourzyme were optimized by BoxBehnken experimental design in terms of hydrolysis yield and DPPH free radicals scavenging activity. ANOVA for linear correlation between DH of peanut protein isolate and DPPH free radical scavenging rate of hydrolyzed peanut protein isolate were further studied. Results showed that the optimal combined ratio of alkaline and trypsin was8:2(m/m), and the optimal hydrolysis conditions were hydrolysis with3.40%(E/S) compound protease at pH8.5and49.36℃for30min followed by173.59min with2%(E/S) Flavourzyme. Under such conditions, the hydrolysis degree and DPPH free radicals scavenging activity was24.40%and80.58%, respectively.Study on the vivo antioxidant activity and hypotensive effect of peanut peptides. The reducing capacity, DPPH· scavenging capacity, O2-·scavenging capacity,·OH scavenging capacity, gel-forming ability, the IR spectra, content of the amino acids of peanut peptides were studied. The results showed that peanut peptides had certain reducing capacity and different scavenging effects on different free radicals. The reducing capacity and free radical scavenging capacity were increased with the increase of peanut peptide concentrations. It can be known that is as same as the peanut protein in amino acids constituted, have the characteristics of enriching in effective amino acids and comparison balance by analysis amino acids of peanut peptides.The monoenzymic mixed peptides were isolated by SephadexG-50, and4kinds of peptide products with different molecular weights were gotten, including F1、F2、F3and F4. Compared the antioxidant ability and ACE inhibitory activities of four fractions, the results showed that the fourth fraction was the best. ACE inhibitory activities and DPPH free radicals scavenging activity of F4was78.18%and86.36%, respectively. The foam property,solubility and foam stability, emulsify stability and emulsify property of the different part of antioxidant peptides of peanut protein isolate were studied respectively. After that, F4was divided into six groups:G1、 G2、G3、G4、G5、and G6by the use G-15. The scavenging rate of G6at the concentration of8mg/mL on DPPH free radicals was up to83.85%. |
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