It is the process of heating every particle of milk products to at least 63°C , and holding at such temperature continuously at least 30 min or heating it to at least 71.5°C and holding at such temperature continuously for at least 15 sec or an approved temperature-time combination that will serve to give a negative phosphatase.
The process of pasteurization is named after a French Scientist, Louis Pasteur, who worked on wine during the years 1860-1870. He observed that heating process improved the quality of wine. Since then application of heat to improve the keeping quality of milk and milk products became a practice and subsequently shortly after 1900 a commercial plant for pasteurization of milk was established in Germany and Denmark. At the present time, the practice of pasteurization of milk is popular throughout the world. Although boiling of milk in homes is a common practice in India, almost all the dairies pasteurize milk before it is supplied. Normally, milk develops acidity which causes spoilage of milk within 4-5 hours of milking. In order to improve the shelf life of this milk, it is necessary that the milk is properly pasteurized. Heating process destroys most of the organisms and growth of those microorganisms which survive heat treatment is retarded due to proper cooling. When the milk is properly pasteurized and the bacterial load is not very high, it is expected that the milk will keep good for nearly 48-50 hours.
Properly pasteurized milk should be completely free from all pathogenic organisms and there should be no danger of milk borne diseases due to consumption of such milk.
Pasteurization involves essentially three steps:
- Heating – to a required temperature.
- Holding – to a required time.
- Cooling – to a sufficiently low temperature.
Objectives of Pasteurization:
- To make milk safe for human consumption.
- To increase the keeping quality of milk.
PROCESSING OF MARKET MILK
HOMOGENIZATION OF MILK:
Homogenization is the process designed to reduce the size of fat globule and making a permanent emulsion of milk fat, serum by the use machine named as homogenizer. Homogenized milk in strict sense is the milk having homogenous character made possible by mechanical means. The process of homogenization was first employed for the manufactured of margarine. Homogenized milk was introduced for the first time in France then in Germany and thereafter it became popular in Europe.
Merits of Homogenization:
- No formation of cream layer/plug.
- Fat in milk does not churn due to rough handling or excessive agitation.
- Better adapted for bulk dispensing, mixing not necessary.
- More palatable perhaps due to brighter appearance heavier body and richer flavor.
- Produces soft curd and is better digestible hence recommended for infant feeding.
- Less susceptible to oxidized flavor development.