研究了羊乳经预热处理后谷氨酰胺转氨酶(transglutaminase,TGase)诱导催化羊乳热稳定性的影响。结果表明,随着预热处理温度的提高和处理时间的延长,羊乳热凝固时间(heat coagulation time,HCT)显著增加(P<0.05);羊乳经60~70 ℃/60 min或80~90 ℃/30 min预热处理可使羊乳中天然TGase抑制剂完全灭活;预热处理可使羊乳中乳清蛋白变性,且随着处理温度的升高,乳清蛋白变性程度增大,这有利于TGase对乳蛋白的交联;十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(sodium dodecyl sulfate-polyacrylamide gel electrophoresis,SDS-PAGE)进一步证实了羊乳中存在天然TGase抑制剂,预热处理可使羊乳中κ-酪蛋白在TGase作用下交联度提高,防止κ-酪蛋白从酪蛋白胶束中解离,进一步提高羊乳的热稳定性。
The effect of transglutaminase (TGase) on the thermostability of goat milk after heat pretreatment was studied. The results showed that the heat coagulation time (HCT) of goat milk significantly increased by increasing temperature and time (P<0.05). Pretreatment of goat milk at 60-70°C for 60 min or at 80-90°C for 30 min could completely inactivate the natural TGase inhibitor in the goat milk and could denature the milk protein. Additionally, the higher temperature the more milk protein was denatured, which was benefit for the cross-linking of milk protein by TGase. The existence of natural TGase inhibitor in the goat milk was further confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Heat pretreatment could increase the cross-linking degree of κ-casein mediated by TGase, which also prevented the dissociation of κ-casein from casein micelles and further improved the thermostability of the goat milk.
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