Dairy products are obtained from or contain milk of mammals such as cattle, goats and sheep.
Milk is often described it contains protein, sugar, fat, vitamins, and minerals.
Milk is a highly nutritious food that serves as an excellent growth medium for a wide range of microorganisms. Food spoilage is an enormous economic problem worldwide. Through microbial activity alone, approximately one- fourth of the world’s food supply is lost. The microbiological quality of milk and dairy products is influenced by the initial flora of raw milk, the processing conditions, and post-heat treatment contamination. Pasteurized fluid milk shelf life is influenced raw milk quality. The microbial and somatic cell count (SCC) of milk will determine the load of heat resistant microbial enzymes in milk. Generally, high levels of psychrotrophic bacteria in raw milk will contribute significant quantities of heat stable proteases and lipases that will break down protein and fat after pasteurization. Thermal processing using more severe conditions than pasteurization but less sever than ultra-high- temperature (UHT) processing; and non-thermal processes such as microfiltration and bactofugation, usually combined with a final thermal pasteurization treatment to meet regulatory requirements. ESL products have been treated in a manner to reduce the microbial count beyond normal pasteurization, packaged under extreme hygiene conditions, and have a defined prolonged shelf life under refrigeration conditions. Longer production runs for niche milk products. Rather than heating the total bacterial count, the process of applying extreme heat and then flash-cooling all within a matter of seconds is known as ultra-pasteurizing, or the process of producing ESL or aseptic items. The shelf life of a dairy products is best defined as the time during which the product remains wholesome and exhibits no physical or organoleptic defects. The reduction in process time due to higher temperature (UHTST) and the minimal come up and cool-down time leads to a higher quality product. Microfiltration is another technique used in the dairy sector for ESL, an alternate to UHT. The determinants of shelf-life of fresh milk are usually the bacterial spoilage which are capable of growth at refrigeration temperature. Seldom do natural milk enzymes or non microbially induced chemical reactions in milk lead to spoilage. Extended shelf-life (ESL) or ultra-pasteurized milk is produced by thermal processing using conditions between those used for traditional high-temperature short-time (HTST) pasteurization and those used for UHT process.