【作者】 丰凡；

【导师】 张国权；

【作者基本信息】 西北农林科技大学 ， 粮食、油脂及植物蛋白工程， 2007， 硕士

【摘要】 荞麦营养丰富,蛋白质含量高,荞麦蛋白具有降低血液胆固醇、抑制脂肪蓄积、抑制乳腺癌和大肠癌的发生、抑制胆结石的形成以及抗衰老等功能特性。利用蛋白酶水解荞麦蛋白,不仅可以更好的利用荞麦蛋白,而且可以获得具有生物活性的荞麦多肽。本文以荞麦蛋白为原料,系统分析了荞麦蛋白的功能特性,确定了荞麦蛋白水解适用酶,并采用单因素试验、二次旋转正交组合试验、SDS-PAGE凝胶电泳等试验和方法,研究了影响荞麦蛋白水解的主要因素及适宜水解条件,初步确定了荞麦多肽的分子量分布、氨基酸组成及抗氧化活性和ACE抑制力。主要研究结果如下:（1）荞麦蛋白谷氨酸含量高,为14.29 g/100g蛋白质,胱氨酸含量最低。荞麦蛋白必需氨基酸平均得分为100分。荞麦蛋白的等电点pI为4.5,持水性随蛋白浓度的降低而下降,起泡性则随蛋白浓度的升高而增加。蛋白浓度为2.0%时的泡沫稳定性最低,乳化稳定性指数ESI为21.07。以水解度为指标,碱性蛋白酶对荞麦蛋白的水解度最高,为30.82%;其次为木瓜蛋白酶,水解度为9.45%。（2）木瓜蛋白酶水解荞麦蛋白的适宜工艺条件为:底物浓度80 g/L、水解温度45℃、酶用量20 000 U/g、pH7.0、水解时间3 h,水解度可达14.38%。各因素对水解度的影响次序依次为水解温度>pH值>酶用量>底物浓度。（3）碱性蛋白酶水解荞麦蛋白的较优工艺条件为:底物浓度18 g/L、水解温度40℃、pH9.8、酶用量为5 500 U/g、酶解时间2 h,水解度达45.63%。各因素对水解度的影响次序依次为酶用量>酶解时间>底物浓度>pH值>水解温度。（4）荞麦蛋白分子量主要分布在20 000～43 000Da之间,荞麦多肽分子量均小于2 300Da,分子量分布较为均匀。与荞麦蛋白相比,多肽的氨基酸的组成比例没有发生明显变化,各氨基酸含量均降低,其中精氨酸含量相差最大为17.03 g/100g氮,蛋氨酸相差最小为1.73 g/100g氮,氨基酸总量相差81.26 g/100g氮。（5）荞麦多肽的羟自由基清除率可达45.40%、ABTS自由基清除率可以达到99.05%、超氧阴离子清除率为80.33%、DPPH清除率达46.6%、亚油酸氧化抑制率最大可以达到84.80%、Fe³⁺还原/抗氧化能力为295.34μmol/L,ACE抑制率为52.37%。除Fe³⁺还原/抗氧化能力外,荞麦多肽的抗氧化活性和ACE抑制率都明显优于荞麦蛋白。更多还原

【Abstract】 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.更多还原