B. - Defense Agents in Bovine Milk

Abstract

This chapter discusses defense agents in bovine milk. Raw bovine milk contains several antimicrobial agents which are beneficial to the calf, primarily in colostrum. It is important to remember that bovine milk is intended to be consumed raw by the calf and should not be considered as an effective conveyer of antimicrobial systems to the human consumer. The antimicrobial agents are lysozyme, lactoferrin, lactoperoxidase, immunoglobulins, vitamin-binding proteins, and lipids. Lactoferrin is one of several proteins which bind iron. Bovine milk contains immunoglobulins. Milk contains proteins which bind vitamin B12, folate, and riboflavin. Proteins are partially denatured by pasteurization. It is therefore unlikely that proteins have any effect on bacterial growth in processed milk which has low bacterial contents and is refrigerated. Gastric lipase can produce microbicidal free fatty acids and monoacylglycerols from milk triacylglycerols in the stomach as can pancreatic lipase in the small intestine. Lactoperoxidase is the only one of these factors that appears to have any effect on milk for human consumption. This is because it can be used to extend the shelf life of milk in developing countries, thus increasing the amount of milk in locales where it is relatively less.