Proteolysis and physicochemical changes in milk on storage as affected by UHT treatment, plasmin activity and KIO3 addition
Proteolysis and physicochemical changes in milk on storage as affected by UHT treatment, plasmin activity and KIO3 addition
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DOI：
10.1016/s0958-6946(99)00128-4
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发表时间：
1999-01-01
影响因子：
3.1
通讯作者：
Kelly, AL
中科院分区：
文献类型：
--
作者：
Enright, E;Bland, AP;Kelly, AL
比较了原料奶、UHT奶、添加KIO3的UHT奶和添加外源纤溶酶使牛奶纤溶酶活性恢复到原来水平的UHT奶的理化性质、蛋白水解性和储存稳定性。牛奶经UHT处理后，变性的β-乳球蛋白与胶束结合在一起(免疫金标记法结合电子显微镜观察)，纤溶酶活性大大降低，而这种牛奶在储存过程中非常稳定。保存的生奶在储存过程中不稳定，并且显示出广泛的蛋白分解，包括明显的非纤溶酶蛋白水解酶的证据。原料奶中胶束的微观形态在储存过程中发生了很大的变化，形成了小的亚胶束颗粒链，储存84d后，从牛奶中恢复了交联的胶束颗粒聚集体。添加KIO3的UHT牛奶在储存过程中表现出与原料奶相似的表现，表现出广泛的纤溶酶原激活、快速的蛋白质分解和沉淀物的形成，其时间和外观与原料奶相似。UHT牛奶加热后加入纤溶酶降低了牛奶的稳定性，增加了蛋白质的分解，并导致沉淀物的早期形成。本研究结果表明，纤溶酶活性对超高温牛奶的贮藏稳定性有重要影响。(C)1999爱思唯尔科学有限公司。保留所有权利。
Physicochemical properties, proteolysis and storage stability of samples of raw milk, UHT milk, UHT milk with added KIO3 and UHT milk in which the original level of milk plasmin activity had been restored by the addition of exogenous plasmin were compared. UHT treatment of milk resulted in association of denatured beta-lactoglobulin with micelles (as demonstrated by immunogold localisation combined with electron microscopy), and greatly reduced plasmin activity, while this milk was extremely stable over storage. Preserved raw milk was unstable over storage, and showed extensive proteolysis, including clear evidence of non-plasmin proteolytic enzymes. The microscopic appearance of micelles in raw milk changed considerably over storage, with the formation of chains of small submicellar particles, and, after 84 d of storage, cross-linked aggregates of micellar particles were recovered from the milk. UHT milk with added KIO3 behaved somewhat like raw milk during storage, showing extensive plasminogen activation, rapid proteolysis and formation of sediments at a similar time, and of similar appearance, to those seen in raw milk. The addition of plasmin to UHT milk after heating reduced the stability of the milk, increased proteolysis, and lead to the early formation of sediments. The results of this study suggest strongly that plasmin activity is a major influence on the storage stability of UHT milk. (C) 1999 Elsevier Science Ltd. All rights reserved.