Pasteurisation, which is essentially a heat treatment that destroys unwanted or disease-causing bacteria without reducing the nutritional quality of milk, is one of the most important safety measures in milk processing. It ensures quality and a longer shelf life, if carried out properly. The two most important factors in pasteurization are temperature and time and has to be specified in relation to the quality of milk and its shelf life.
Why should I be aware of this?
Though pasteurization kills harmful bacteria in milk, new bacteria are introduced as soon as the container is opened. Over time these bacteria grow large enough to spoil the milk.
Pasteurized milk and health
Heat used in the pasteurization process helps destroy harmful bacteria without significantly changing milk's nutritional value or flavor. Pasteurization not only kills disease-causing bacteria, but destroys bacteria that cause spoilage, extending the shelf life of milk.
Milk can become contaminated on the farm when animals shed bacteria into the milk. Cows, goats, and sheep carry bacteria in their intestines that do not make them sick but can cause illness in people who consume their untreated milk or milk products. 
Opponents of pasteurization say that it makes insoluble the major part of the calcium contained in raw milk, leading to rickets, bad teeth and nervous troubles. Sufficient calcium content is vital to children, and with the loss of phosphorus also associated with calcium, bone and brain formation suffer serious setbacks.
It is also claimed that pasteurization destroys 20 percent of the iodine present in raw milk, causes constipation and generally takes from the milk its most vital qualities.
The anti-pasteurised milk lobby commonly claims that heating milk to high temperatures can result in the following health and nutrient issues:
- The denaturing of milk proteins, making them less usable and even harmful to your body;
- The destruction of enzymes in the milk, including phosphatase and lactase. They claim that without these two enzymes milk is not absorbed or digested well and may result in "lactose intolerance". A decrease in the amount of soluble calcium;
- The destruction of vitamins B12, B6, and C; and the
- Destruction of beneficial bacteria in the milk.
Raw milk advocates attribute stronger immune and better digestive systems to raw milk, and also aver that it tastes much better than pasteurised milk.
- Milk processing
- ↑ Got Milk? Make Sure It's Pasteurized