Study On Preparation Of Peanut Oligopeptides And Its Functional Activities

The factors affected the preparation of peanut oligopeptides were studied. The regression models were established between the indexes, including TCA-NIS and DH, and the factors that affect the preparation of peanut oligopeptides by orthogonal rotation design. Based on it, Alcalase was chose to hydrolyze peanut protein. According to experiments and need of practice, The factors were optimized: temperature 53℃, substrate concentration 4%, Alcalase dosage 3637 U/g, time 105min, pH values 8.0. while TCA-NIS was. 80.35%, DH was 17.72.The factors affected hydrolyzing peanut protein by compound enzymes were studied based Alcalase hydrolysis of peanut protein. The regression models were established between the TCA-NIS and the factors that affect the preparation of peanut oligopeptides by homogeneous design. Based on it, N120P was chose to hydrolyze peanut protein after Alcalase. The optimum conditions were obtained: time 65min, temperature 57℃, N120P dosage 2061 U/g, pH values 6.0, white TCA-NIS was 89.01%, DH was 23.76%Based on it, the enzymatic hydrolysis kinetics of peanut protein was studied. The model of Alcalase hydrolysis kinetics was built: R=254.65E₀exp[-0.3352(DH)], the kinetic constants: a=254.65E₀/S₀,b=0.3352, K₂=254.65 min^-1, inactivation constants of Alcalase is 84.777min^-1. The model of N120P hydrolysis kinetics after Alcalase was built: R=(9.46563E₀+0.14519)exp[-0.2629(DH)],the kinetic constants: a=9.46563e₀/S₀+0.14519,b=0.2629, K₂=9.46563 min^-1, inactivation constants of Alcalase is 2.60511 min^-1The desalting method by cation exchange resins and anion exchange resins mixed bed was built to improve purity of peanut oligopeptides. The optimum conditions were obtained: hydrolyte flow rate 5-10 BV/h, pH value of hydrolyte 4.5 and between anion exchange resins and cation exchange resins 3:2. while the desalting rate and oligopeptide recovery rate were all above 80%, the effect was better than traditional desalting method. The purity of desalting peanut oligopeptides was 90.25%, the molecular weight distribution was between 126～949Da and the contents of free amino acid was 1.64mg/g.Peanut oligopeptides were separated by ultra-filtration technology to acquire oligopeptides of different molecular weight distribution. The results show that the optimum conditions of the first-degree ultra-filtration are 5%～7.5% peptides, pressure 0.18 MPa, temperature 35℃and the optimum conditions of the second-degree ultra-filtration are 7.5% peptides, pressure 0.21 MPa, temperature 40℃. After separation with ultra-filtration, the recovery rate of peanut oligopeptides below 1 KD was 25.02%.antioxidative activity and ACE inhibitory activity of peanut oligopeptides was evaluated by chemical models. The results showed that peanut oligopeptides had antioxidative activity and ACE inhibitory activity, of which ACE inhibitory activity stands out very much, and its IC₅₀ value 0.517mg/ml.Desalting of peanut oligopeptides can increase its ACE inhibitory activity, ultra-filtration of peanut oligopeptides can enrich the ACE inhibitory oligopeptides, of which IC₅₀ value of the peanut oligopeptides below 1KD was 0.255 mg/ml.Peanut oligopeptides below 1KD were found to belong to competitive inhibition to ACE and they could resist hydrolysis of digestive enzyme by mechanism research. The SBP of SHRs were reduced markedly by peanut oligopeptides below 1KD and the heart rate of SHRs were not influenced. Peanut oligopeptides below 1KD could steadily reduce SBP of SHRs and could be absorbed completely to enter blood circulation.The scatter diagram and nonlinear regression model were built to discuss the connection between amino acid composition of protein and ACE inhibitory activity of hydrolysate of protein. The results showed that the contents of uncharged-side chains amino acids, basic amino acids and acidic amino acids did not influence ACE inhibitory activity of hydrolysate of protein, while the proteins with high contents of hydrophobic, aromatic and branched-side chains amino acids are more suitable sources for the preparation of ACE inhibitory peptides.The parameters of manufacturing process of peanut oligopeptides were amplified based on above research. The results showed that the hydrolysate of peanut protein must be pre-desalting by nanofiltration. Nanofiltration membranes of the molecule weight cut-off 150Da was chose, the extension rate of hydrolysate of peanut protein was 10 times during nanofiltration. The purity of peanut oligopeptides manufactured by amplified experiment was above 85%; the total recovery rate of peanut oligopeptides was 28.4%. The ACE inhibition IC₅₀ value of peanut oligopeptides below 1KD was 0.237 mg/ml. So the manufacturing process of peanut oligopeptides can be applied to peanut oligopeptides industrialization.