Abstract Next to the widely studied glycation and Maillard reaction cascade, the heat treatment of milk during production of long shelf-life products may induce side reactions where serine, phosphoserine, glycoserine, cysteine or cystine can be converted into dehydroalanine, which in turn can further react with lysine, histidine or cysteine to yield lysinoalanine (LAL), histidinoalanine (HAL) or lanthionine (LAN) cross-links. The nutritional value, digestibility and functionality of the proteins may be affected by the introduction of covalent cross-links, modified amino acid residues and eventually aggregation. In this study, a liquid chromatography triple quadrupole based method was developed to directly quantify LAL and LAN using multiple reaction monitoring. The method was validated and applied to investigate the content of these cross-links in different dairy products. The level of LAL and LAN was below quantification in raw milk and pasteurised milk, but increasing amounts were measured in ultra-high temperature milk and micellar casein isolate.

中文翻译：

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乳制品中赖氨酸丙氨酸和羊毛硫氨酸绝对定量的多反应监测质谱法的开发与应用

摘要 除了广泛研究的糖基化和美拉德反应级联之外，在生产长保质期产品期间对牛奶进行热处理可能会引起副反应，其中丝氨酸、磷酸丝氨酸、甘油、半胱氨酸或胱氨酸可以转化为脱氢丙氨酸，进而进一步与赖氨酸、组氨酸或半胱氨酸反应生成赖氨酸丙氨酸 (LAL)、组氨酸丙氨酸 (HAL) 或羊毛硫氨酸 (LAN) 交联。蛋白质的营养价值、消化率和功能可能会受到共价交联、修饰的氨基酸残基和最终聚集的影响。在本研究中，开发了一种基于液相色谱三重四极杆的方法，可使用多反应监测直接量化 LAL 和 LAN。该方法经过验证并应用于研究不同乳制品中这些交联的含量。LAL 和 LAN 的水平在原料奶和巴氏杀菌奶中低于定量，但在超高温奶和胶束酪蛋白分离物中测得的含量增加。