Exploring new methods of processing milk

探索牛奶加工新方法

• 批准号: 122941-2008
• 负责人: Lencki, Robert
• 金额: $ 2.1万
• 依托单位: University of Guelph
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2012
• 资助国家: 加拿大
• 起止时间: 2012-01-01 至 2013-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=496795
• 关键词: Exploring; new; methods; processing; milk

The standard manner by which raw milk is processed throughout the world involves pasteurization (to destroy all human pathogens) and homogenization (to reduce fat globule size to prevent creaming). In Canada, provincial laws require that all milk be pasteurized, because raw milk can harbour dangerous microbes such as M. paratuberculosis, L. monocytogenes and E. coli. Despite this danger, a growing number of consumers wish to drink raw milk because they feel that current processing methods alter the sensory and nutritional qualities of the milk. Pasteurization does destroy enzymes and immunoglobulins and several of these proteins are known to have health benefits. High temperatures also facilitate interactions between the whey protein beta-lactoglobulin and kappa-casein, which inhibits rennet activity and alters the texture of cheeses and yoghurt. Complex formation also hinders the production of protein peptides during aging, thereby altering the sensory qualities of the final cheese. Connoisseurs know that cheeses produced from raw milk are often superior in taste and texture to those coming from pasteurized milk. The homogenization step also alters the structure of the skim milk membranes (SMM) present in raw milk, thereby changing its mouth feel. This project will specifically look at how heat treatment and homogenization alters milk structure. The applicant has recently published work that was the first to show that casein micelles have a fibril-like structure (J. Dairy Sci. 90:75-89 (2007)) and has proposed a new micelle stabilization mechanism that is consistent with this casein fibril model. Consequently, this study will first explore how casein micelle fibril structure is altered by elevated temperatures alone and in the presence of beta-lactoglobulin. Next, the applicant will examine several simple separation techniques (membrane filtration, precipitation, flotation) that can be used on raw milk to remove the various valuable yet unstable components before further processing. These fractions could then be used as valuable food ingredients or reintroduced into the milk after human pathogens have been destroyed to produce healthier and more functional dairy products.

世界各地加工原奶的标准方式包括巴氏灭菌（以消灭所有人类病原体）和均质化（以减少脂肪球大小以防止乳化）。 在加拿大，省级法律要求对所有牛奶进行巴氏灭菌，因为生牛奶可能含有危险的微生物，如副结核分枝杆菌、单核细胞增生李斯特菌和大肠杆菌。 尽管存在这种危险，但越来越多的消费者希望饮用原奶，因为他们认为当前的加工方法改变了牛奶的感官和营养品质。 巴氏灭菌确实会破坏酶和免疫球蛋白，并且已知其中一些蛋白质对健康有益。 高温还促进乳清蛋白β-乳球蛋白和κ-酪蛋白之间的相互作用，从而抑制凝乳酶活性并改变奶酪和酸奶的质地。 复合物的形成还会阻碍老化过程中蛋白肽的产生，从而改变最终奶酪的感官品质。 鉴赏家知道，用生奶生产的奶酪在味道和质地上通常优于用巴氏杀菌奶生产的奶酪。 均质步骤还会改变原料奶中脱脂乳膜 (SMM) 的结构，从而改变其口感。 该项目将专门研究热处理和均质化如何改变牛奶结构。 申请人最近发表了第一个证明酪蛋白胶束具有原纤维样结构的工作(J.Dairy Sci.90:75-89(2007))，并提出了与该酪蛋白原纤维模型一致的新的胶束稳定机制。 因此，本研究将首先探讨单独升高温度和存在 β-乳球蛋白时酪蛋白胶束原纤维结构如何改变。 接下来，申请人将研究几种可用于原奶的简单分离技术（膜过滤、沉淀、浮选），以在进一步加工之前去除各种有价值但不稳定的成分。 这些部分可以用作有价值的食品成分，或者在人类病原体被消灭后重新引入牛奶中，以生产更健康、功能更强的乳制品。