【作者】 李艳伏；

【导师】 徐怀德；

【作者基本信息】 西北农林科技大学 ， 食品科学， 2008， 硕士

【摘要】 核桃具有很高的营养价值和药用价值,是开发高级保健食品的良好原料。本论文用不同蛋白酶酶解核桃粕蛋白,测定了酶解产物的特性、抗氧化性及体外ACE抑制功能,采用Sephadex G-25对蛋白酶酶解产物进行了分离,测定了不同分子片段多肽的功能特性。取得以下结果:木瓜蛋白酶酶解核桃粕蛋白质最佳的酶解条件为酶解温度为65℃,pH为6.5,底物浓度为3%,加酶量（E/S）为7000 u/g,用超声波功率750w的60%预处理12min。碱性蛋白酶酶解核桃粕蛋白质的最佳的酶解条件为酶解温度为55℃,pH为8,底物浓度为3%,加酶量（E/S）为4000 u/g,用超声波功率750w的50%预处理9min。在最佳酶解条件下木瓜蛋白酶酶解核桃粕蛋白180min,酶解液的乳化能力和乳化稳定性分别为140.7和20.8最高值;木瓜蛋白酶酶解产物中5733～1321Da片段的多肽其乳化性能和乳化稳定性最好,分别为165.6、19.5。碱性蛋白酶酶解核桃粕蛋白,在最佳酶解条件下酶解120min时酶解液的乳化能力最大为157.6,150min时乳化稳定性最高为21.8。碱性蛋白酶酶解产物中5733～1321Da的多肽乳化能力最高值为165.6, 12384～5733Da的多肽乳化稳定性最好为19.7。在最佳的酶解条件下木瓜蛋白酶酶解核桃粕蛋白210min,酶解液的抗氧化活性较高,其中OH·清除率为55.43%,O₂^-·清除率为64.23%,DPPH·清除率79.32%,总抗氧化能力98.74单位/ml。分子量在1321～607Da片段的多肽其抗氧化性较好,OH·清除率为42.26%,O₂^-·清除率57.33%,DPPH·清除率为74.43%,总抗氧化能力88.43单位/ml。在最佳酶解条件下,碱性蛋白酶酶解核桃粕酶解210min的酶解液的OH·清除率为72.3%;总的抗氧化能力为171.579单位/ml;O₂^-·清除能力为83.1%,DPPH·清除能力为102.6%。抗氧化性多肽主要集中在1321～612Da之间,占整个多肽含量的13.22%;O₂^-·清除率为62.57%,OH·清除率为70.23%、DPPH·清除率为99.56%,总抗氧化能力为118.987单位/ml。浓度为300mmol/L的NaCl和100mmol/L硼酸盐缓冲体系对ACE活性保护最好。通过响应面分析得出木瓜蛋白酶最佳的酶解条件为温度50℃,pH为7.5,底物浓度为3%;加酶量（E/S）为6000 u/g,酶解时间为240min,酶解液对ACE抑制较好;其分子量分布在612-307Da的多肽ACE抑制率最大为93.56%,该片断占整个酶解液多肽片段的9.81%,总的游离氨基酸含量占该多肽片段含量的8.431%,含量最高的氨基酸为亮氨酸（Leu）。碱性蛋白酶解的最佳条件为温度40℃,pH为8.5,底物浓度为3%,加酶量（E/S）为5000 u/g,酶解时间为150min,酶解液对ACE抑制较好;其分子量分布在1321-612Da多肽ACE抑制率最大为93.27% ,该片断占整个酶解液多肽片段的15.12%,总的游离氨基酸含量占该多肽片段含量的0.062%,含量最高的氨基酸为脯氨酸（Pro）。更多还原

【Abstract】 There are quite high nutrition and medicine values in walnut and it is the favaroble material of health food.In recent years, walnut’s production was quickly increasing, bringing favaroble opportunities to walnut’s deep-processing.To know walnut’s nutrition and health care function sciencly, using walnul as material , walnut protein was enzyme hydrolyzed by papain and Alcalase,mainly researching on some hydrolytic properties,the antioxidant functional properties and ACE inhibitory ratio in vitro of hydrolysates. papain and Alcalase hydrolysates were separated. The main results are as follows:For hydrolysates, with time’s extension, the content of amino nitrogen, the degree of solubility, the degree of hydrolysis, and peptides content were all increased, the average length of peptides chains were decreased gradually, the scavenging ability of free radical and the ability of deoxidization were also increased. By compareing, papain protease was the optimum protease.Antioxidative activity of hydrolysates, which come from walnut protein by the Papain enzyme was studied.yied of antioxidative Activity of hydrolysates of different hydrolysis time and the different groupof molecular weight of peptides were studied.[Result] in the optimum reaction conditions of enzyme : dosage of enzyme 6000U/g,substrate concentration3% ,pH 8.5,temperature 55℃with 210 min reaction time ,the yied of hydrolysates have strong anti-oxidized ability: 55.43% of scavenging rate of OH·, 64.23% of scavenging rate of O₂^-·, 79.32% of scavenging rate of DPPH·, 98.74% OD/ml of total anti-oxidized ability. the different group of molecular weight of peptides was also studied and the result show that 1321～607Da have strong anti-oxidized ability: 42.26% of scavenging rate of OH·, 57.33% of scavenging rate of O₂^-·, 74.43% of scavenging rate of DPPH·, 88.43 OD/ml of total anti-oxidized ability. hydrolysates with the optimum hydrolysis time of 210 min and 1321～607Da molecular weight of peptides have strong ability of antioxidative activity .Antioxidative activity of hydrolysates ,which come from walnut protein by the Alclase enzyme was studied. yied of antioxidative Activity of hydrolysates of different hydrolysis time and the different groupof molecular weight of peptides were studied.in the optimum reaction conditions of enzyme : dosage of enzyme 3000U/g, substrate concentration 4%,pH 8.5,temperature 50℃with 210 min reaction time ,the yied of hydrolysates have strong anti-oxidized ability: 72.3% of scavenging rate of OH·, 83.1% of scavenging rate of O2-, 102.6% of scavenging rate of DPPH·, 162.986OD/ml of total anti-oxidized ability. the different groupof molecular weight of peptides was also studied and the result show that 1321～607Da have strong anti-oxidized ability: 70.23% of scavenging rate of OH·, 62.57% of scavenging rate of O2-, 99.56% of scavenging rate of DPPH·, 118.987 OD/ml of total anti-oxidized ability. hydrolysates with the optimum hydrolysis time of 210 min and 1321～607Da molecular weight of peptides have strong ability of antioxidative activity .We did orthogonal trial with the ACE inhibitory ratio. The hydrolysate by Papain enzyme with the ACE inhibitory ratio, was gained under the condition of temperature 50℃, pH 7.5, enzymatic hydrolysis time 240min, substrate and substrate concentration 3.0%. Trough separateing by SephadexG-25, the fraction 612-307Da with the higher activity were collected, with the ACE inhibitory ratio being 93.56% . We did orthogonal trial with the ACE The hydrolysate by Alclase enzyme with the ACE inhibitory ratio, was gained under the condition of temperature 40℃, pH 8.5, enzymatic hydrolysis time 150min, substrate and substrate concentration 3.0%. Trough separateing by SephadexG-25, the fraction 1321-612Da with the higher activity were collected, with the ACE inhibitory ratio being 93.27% .更多还原