生鲜羊乳脂肪酶活力研究

Studies on Lipase Activity of Fresh Goat Milk

脂肪酶可使羊乳中脂肪发生脂解反应产生游离脂肪酸,进而影响羊乳风味变化。乳中脂肪酶分为内源性脂肪酶和外源性脂肪酶。内源性脂肪酶主要是脂蛋白脂肪酶,外源性脂肪酶主要是微生物脂肪酶。通过对不同品种、不同泌乳阶段生鲜山羊乳脂肪酶活力比较,确定对生鲜羊乳风味变化起主要作用的脂肪酶来源;通过对羊乳和牛乳中脂肪酶活力的比较,分析牛羊乳风味差异的原因。方法:以关中常乳、关中初乳、萨能常乳和荷斯坦牛常乳为研究对象,用脂蛋白脂肪酶酶联免疫试剂盒测定羊乳中脂蛋白脂肪酶活力,并采用分光光度计法测定微生物脂肪酶活力。结果:关中常乳和萨能常乳脂蛋白脂肪酶活力差异不显著;关中初乳和关中常乳脂蛋白脂肪酶活力差异显著;山羊乳中内源性脂肪酶活力显著高于外源性脂肪酶活力;羊乳常乳和牛乳常乳中脂蛋白脂肪酶活力在脂肪相和脱脂乳相的活力分布不同。结论:对生鲜山羊乳风味变化起主要作用的脂肪酶是内源性脂肪酶。羊乳与牛乳中脂蛋白脂肪酶活力在脂肪相和脱脂乳相中的差异,可能是导致牛羊乳风味差异的因素之一。

Goat milk can produce free fatty acids by lipase＇s lipolysis, which will have an effect on the goaty fla- vor. Lipases in milk can be classified into two categories, endogenous lipase and exogenous lipase. The endogenous li- pases are mainly lipoprotein lipase, while the exogenous lipases are from microorganism. Objectives： Comparing the ac- tivity of lipase among different species, different stages of lactation to investigate the causation of the goat milk off-fla- vor. And the reasons for the differences between goat milk and cow milk can be discovered through the comparison of goat milk and cow milk. Methods： Guanzhong colostrum, Saanen mid-lactation milk ,Guanzhong mid-lactation milk and Holstein cow mid-lactation milk were compared. The lipoprotein lipase ELISA kits were used to determinate the activity of lipoprotein lipase. And the activity of microbial lipase activity were measured by using a speetrophotometer method. Results： The activity of lipoprotein lipase showed no significant difference between Saanen mid-lactation milk and Guanzhong mid-lactation milk; The activity of lipoprotein lipase showed significant difference between Guanzhong colostrum and Guanzhong mid-lactation milk; The endogenous lipase has a significant higher activity than exogenous li- pase. The distribution of lipoprotein lipase activity in the cream and skim milk are different between goat milk and cow milk. Conclusions： the endogenous lipase plays a major role in off-flavor of fresh goat milk. The differences of lipase ac- tivity between goat milk and cow milk in the cream phase and skim milk phase can be used to explain the difference of goaty flavor and cow flavor.