体外消化过程中蛋白质品质与寡肽释放的研究

应用胃蛋白酶 胰酶两步体外消化法测定 6种豆饼 (粕 )、3种鱼粉、菜籽饼、玉米蛋白粉、肉粉、蚕蛹、酪蛋白等 1 4种蛋白质饲料的寡肽释放量 ,并研究了它们与蛋白质质量和氨基酸组成间的关系。结果表明 :酪蛋白、鱼粉、豆饼 (粕 )的寡肽释放量最高 ,贮藏的鱼粉及加热、贮藏过的豆粕、饼寡肽释放量降低 ;寡肽释放量与饲料赖氨酸、有效赖氨酸、异亮氨酸呈正相关 (r =0 .86～ 0 .93,P <0 .0 1 )。鱼粉、豆饼、蚕蛹、菜子饼寡肽平均链长在 5～ 6之间 ,新鲜豆粕、酪蛋白、玉米蛋白粉链长为 7.5、8.4、1 1 .4 ,大分子肽含量较高 ;植物饲料的寡肽中非必需氨基酸 (NEAA)占总氨基酸的 5 0 %～ 70 % ,必需氨基酸 (EAA)相对较低 ;动物性饲料NEAA比例仅略高于EAA。所有饲料释放的FAA不到总氨基酸的 1 % ,其中主要是EAA ,饲料中含有效碱性氨基酸的真蛋白与饲料总真蛋白的比值 (CBBG/TP)与寡肽和FAA的释放量呈显著线性相关 (r=0 .92和 0 .87) ,寡肽释放量和CBBG/TP均较好地反映了蛋白质质量。

Study on Oligopeptides and Free Amino Acids Released fr om Proteins in vitro

Two tep in vitro digestion technique using pepsin and pancreatin was employed to determine the protein digestibility, that the amount of oligopeptides and free amino acids(FAA) released from 14 protein feeds. The results of HPLC analysis indicated that the amount of oligopeptides released in vitro from casein, soybean meals(exp), fish meal(2),rapeseed meal were significantly higher (p<0.01～0.05) than those from meat meal, corn gluten meal and soybean meals which were over heated or stored for 6 years. The average length of oligopeptides chain corresponding protein in soybean meal (1#,exp.), fish meal, silkworm chrysalis and rapeseed meal were 5.2,5.8,4.9 and 5.9, less than that of soybean meal(2#sol), corn gluten meal and casein (7.5,8.4 and 11.4), The value of CBBG/TP is a ratio of the efficient true protein content to the total true protein content of the feeds. There was significant correlation between CBBG/TP and digestibility of animal proteins (r=0.84,\{P<0.01)\}. The value of CBBG/TP and the amount of oligopeptides may be a parameter to indicate the protein quality.