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饲料产品发生非酶褐变后影响脊椎动物胃蛋白酶的活性,严重褐变产品(BHP’s)与胃蛋白酶形成蛋白质共沉淀物的多少取决于p H、离子强度和蛋白质的等电点。水产饲料制造过程和饲料原料的制造过程均需加热,易产生褐变。目前研究已表明饲料中葡萄糖和甘氨酸混合物的形成褐变产物对虹鳟鱼胃蛋白酶的不利影响。试验结果表明,BHP’s与胃蛋白酶反应形成蛋白质共沉淀物,降低鱼胃中蛋白酶活性。在试验过程中,胃蛋白酶活性损失最高可达20%。在反应过程中,pH和离子强度有依赖性相互作用,这种作用相对稳定,能抵抗一定的机械振动。当饲料褐变浓度在500~1 000μg·mL~(-1),pH为3.5时,pH和离子强度可产生依赖性相互作用,胃蛋白酶活性损失最高可达20%;而pH为4.0时,p H和离子强度无相互作用。当离子强度为100 mM时,在单价离子(NaCl)的作用下,相互作用减弱。二价阳离子如Ca~(2+)、Mg~(2+)等在30~80 mM时,即离子强度<100 mM,同样会扰乱BHP’s和胃蛋白酶的相互作用,减轻BHP’s的影响。
The non-enzymatic browning of the feed product affects vertebrate pepsin activity. The amount of coprecipitates formed by the severe browning product (BHP’s) and pepsin depends on the p H, the ionic strength and the isoelectric point of the protein. Aquaculture feed manufacturing process and feed raw materials manufacturing process needs heating, easy to produce browning. Current research has shown that the formation of browning products in the feed mixture of glucose and glycine adversely affects rainbow trout pepsin. The results show that BHP’s react with pepsin to form protein coprecipitate and reduce protease activity in fish stomach. During the test, pepsin activity loss up to 20%. During the reaction, pH and ionic strength have a dependent interaction, this effect is relatively stable, can resist a certain degree of mechanical vibration. When the feed browning concentration was 500-1 000μg · mL -1 and pH was 3.5, the pH and ionic strength could produce the dependent interaction, and the loss of pepsin activity could reach up to 20%. At pH 4.0, There is no interaction between p H and ionic strength. When the ionic strength is 100 mM, the interaction is weakened by monovalent ions (NaCl). Divalent cations such as Ca 2+ and Mg 2+ at 30-80 mM ie ionic strength <100 mM also disrupt the interaction between BHP’s and pepsin and reduce the effects of BHP’s.