Mehta Bhavbhuti M, Deeth Hilton C
Dairy Chemistry Dept, SMC College of Dairy Science, Anand Agricultural Univ, Anand-388110, Gujarat, India.
School of Agriculture and Food Sciences, The Univ. of Queensland, Brisbane, Qld 4072, Australia.
Compr Rev Food Sci Food Saf. 2016 Jan;15(1):206-218. doi: 10.1111/1541-4337.12178. Epub 2015 Nov 13.
Lysine residues in milk proteins become "blocked" when they react with reducing sugars, particularly lactose, in the Maillard reaction. The blocked or glycated lysines reduce the biological availability of the lysine to metabolic processes and also hinder hydrolysis of the parent protein by digestive enzymes. Heating and storage of milk and milk products are the major promotants of the Maillard reaction and resulting chemical damage to the proteins. Several methods have been proposed to estimate the extent of this protein damage. Two major compounds, furosine, a product of acid hydrolysis of lactulosyl-lysine, the 1st stable product of the Maillard reaction, and carboxymethyl-lysine are used for assessing the early and advanced stages of the Maillard reaction, respectively. In addition, several methods are used for assessing the bioavailability of lysine in a protein; these include chemical, enzymic, and animal-based methods. This review discusses the Maillard reaction and its significance in milk and dairy products, methods of assessing the extent of the reaction and of the bioavailability of lysine, and the nutritional significance of blocked lysines and associated Maillard reaction products in milk proteins.
在美拉德反应中，乳蛋白中的赖氨酸残基与还原糖（尤其是乳糖）发生反应时会被“封闭”。被封闭或糖化的赖氨酸会降低赖氨酸在代谢过程中的生物利用率，还会阻碍消化酶对母体蛋白质的水解。牛奶及奶制品的加热和储存是美拉德反应及由此导致蛋白质化学损伤的主要促进因素。已经提出了几种方法来估计这种蛋白质损伤的程度。两种主要化合物，即乳果糖赖氨酸（美拉德反应的第一个稳定产物）酸水解产物呋喃素和羧甲基赖氨酸，分别用于评估美拉德反应的早期和晚期阶段。此外，有几种方法用于评估蛋白质中赖氨酸的生物利用率；这些方法包括化学法、酶法和基于动物的方法。本综述讨论了美拉德反应及其在牛奶和奶制品中的意义、评估反应程度和赖氨酸生物利用率的方法，以及牛奶蛋白中被封闭的赖氨酸和相关美拉德反应产物的营养意义。
