Influence Of Heat Resistant Enzymes And Milk Components On The Stability Of UHT Milk

UHT(Ultra High Temperature) processed milk is a long shelf life liquid milk product, which is sterilized in 135～150℃. Consumers prefer UHT milk by its nourishment enrich, long shelf life, easy to carry and drink.Coagulation is a common phenomenon in UHT milk. And the real reason is not sure in the world. The research indicated that not all milk enzymes were destroyed by UHT processing. Proteolysis and lipolysis enzymes hydrolyzed milk protein and fat, led to increase of milk viscosity and acidity, tendenced to coagulation, but didnot emerge coagulation during storage for 150 days.Fat separation is another general phenomenon during UHT milk storage. There are several factors have an effect on it, such as the quantity of milk fat, storage in a high temperature and enzymes. The study showed that the more degree of milk protein hydrolized, the more severity of fat separation. The value of milk fat to protein affected the fat separation. The higher of the compare of milk fat and protein, the more severity of fat separation. When milk fat is relatively lower to milk protein, the fat separation can be weaken by mixing some emulsifier properly, but cannot eliminate this phenomenon. High pressure processing made milk fat globe smaller and well-distributed ,and it is good for milk quality during storage.