Study On Preparation And Bioactivities Of Buckwheat Peptide

Buckwheat is affluent in nutrition and it contains abundant protein. Buckwheat protein has more functional components than other cereal protein, such as cholesterol decrease, fat suppression, colonic cancer inhibition, cholelithiasis inhibition and so on. The study used protease to hydrolyze buckwheat protein,which was able to not only take good use of buckwheat protein, but also get the bioactive peptides of buckwheat. The study took buckwheat protein as the raw material, systematic analyzed the functional characteristic of buckwheat protein, chose the optimum protease for hydrolyzation, studied the main factors and optimum conditions of hydrolyzation by mono-factor analysis and quadratic rotation-orthogonal combination experiment, studied the convergence of molecular weight of buckwheat protein by SDS-PAGE gel electrophoresis, got the convergence of molecular weight of buckwheat peptides, amino acid composition, antioxidation and inhibition ratio of ACE. All the results as below:(1) Glutamic acid was the highest amount amino acid in buckwheat protein, about 14.29 g/100g protein, and cystine was the lowest. The average score of essential amino acid of buckwheat protein was 100 points. The isoelectronic point of buckwheat was 4.5. Water retention decreased with the concentration decreasing of the protein, but the foamability was just the opposite. Stability of foam was the lowest at the concentration of 2.0%,and the index of emulsify stability was 21.07. Taking the DH as the criteria, alkaline protease was the best protease and its DH can reach 30.82%, followed by papaya protease, its DH was 9.45%.(2) The optimum conditions for papaya protease hydrolyzing the buckwheat protein were: 80 g/L of substrate concentration, 45℃temperature, 20 000 U/g of protease dosage, pH7.0, 3 h hydrolyzation . The DH can reach 14.38% under the conditions. The sequence of the factors which impacted hydrolyzation was: hydorlyzing temperature > pH > protease dosage > subst- rate concentration.(3) The optimum conditions for alkaline protease hydrolyzing the buckwheat were: 18 g/L of substrate concentration, 40℃temperature, 5 500 U/g of protease dosage, pH9.8, 2 h hydrolyzation time. The DH can reach 45.63% under the conditions. The sequence of the fact- ors which impacted hydrolyzation was: protease dosage > hydrolyzing time > substrate conce- ntration > pH> hydorlyzing temperature. (4) The molecular weight of buckwheat protein converged between 20 000 Da and 43 000 Da, and buckwheat peptides were lower than 2 300 Da with homogeneous distributi- on. The composition and proportion of amino acid of buckwheat peptides had no remarkable change comparing with buckwheat protein, all the amino acid content decreased, the differe- nce of arginine was greatest, about 17.03 g/100g nitrogen equivalent, the methionine was minimum, about 1.73g/100g nitrogen equivalent, and the total of amino acid decreases was 81.26 g/100g nitrogen equivalent.(5) Scavenging ratio to hydroxyl radical of buckwheat peptide can achieve 45.40%, scavenging ratio to ABTS radical can achieve 99.05%, superoxide anion radical 80.33%, Scavenging ratio to DPPH 46.6%, inhibitory rate of linolic acid oxidation can reach 84.80%, the ability of Fe³⁺ deoxidizing/antioxidation is 295.34μmol/L, inhibiting ratio for ACE is 52.37%. Both the abilities of antioxidation and ACE inhibition of buckwheat peptide are better than buckwheat protein, excluding the ability of Fe³⁺ deoxidizing/antioxidation.