乳中蛋白酶与UHT乳贮存中的胶凝现象

乳中的蛋白酶有2个主要的来源途径，乳中天然存在的蛋白酶和由某些微生物产生的蛋白酶，其中纤维蛋白溶酶和嗜冷菌产生的耐热性蛋白酶是存在于UHT乳中的主要蛋白酶，这些蛋白酶非常耐热，经UHT灭菌处理仍可存活。耐热性蛋白酶在UHT乳贮存中水解乳蛋白质从而导致了UHT乳的胶凝．简要介绍了纤维蛋白溶酶、嗜冷菌耐热性蛋白酶的性质、活性测定方法，论述了这些酶引起的UHT乳的胶凝性质、形成原因及影响因素，并提出了一些防止措施。

Proteases in milk and gelation of UHT milk

Protease of UHT milk can be attributed to two main sources,native protease and proteases produced by microorganisms present in the milk.Plasmin and proteases of psychrotrophic bacteria are main proteases present in the UHT milk.These proteases are quite heat stable and capable of partially surviving UHT treatment.Gelation of UHT milk is thought to be initiated by proteolysis of milk proteins by these heat resistant proteases.The properties,determination of plasmin and proteases of psychrotrophic bacteria are introduced in this paper;gelation properties,causation and preventing measurement are discussed.