The ability to alter the activity of these antimicrobial factors in cow milk could have an impact on shelf-life of raw milk and development of additional health and functional foods based upon these factors. In addition to its value as a nutrient source, interest has arisen in the ability of milk to kill bacteria and in how this knowledge can be applied to mastitis control, human health, and functional foods for people. A number of proteins found in milk under various conditions exhibit antimicrobial activity. The young of many mammalian species are not born with an effective immune system. The immunoglobulins protect the neonate from infection until their own immune system is developed.
Immunoglobulins are a component of the natural defense mechanism.
They are synthesized in response to the presence of foreign particles, such as bacteria and viruses. The synthesis process is specific for the foreign particle that is present, resulting in an immunoglobulin structure that is capable of recoginzing the foreign particle and eliminating it from the body. Immunoglobulins are found in high concentrations in colostrum, the first milk, and in low concentrations in milk. In addition to the immunoglobulins, other proteins found in milk are thought to have antimicrobial activities. Lactoferrin is present in large quantities in mammalian secretions such as milk, tears, saliva, and seminal fluid, as well as in some white blood cells.