Milk comes from cow at about 37°C and must be cooled within two hours to 4°C or lower and under hygienic condition. At this temperature any microorganism present will not multiply at dangerous rate and milk can be transported to processing plant safely. Whole milk for human consumption is pasteurized at 75°C for short time and then again cooled to 4°C immediately. During processing of dairy and dairy products and its storage, refrigeration temperature should be maintained in number of stages. Refrigeration is a basic requirement for processing and storage of milk and milk products as majority of dairy products are perishable in nature. The need of refrigeration is listed blow
1. Chilling of milk at producer’s level by employing bulk milk coolers and at milk chilling centers is the first requirement in the dairy industry. Immediate cooling of milk to about 2 – 3°C is very important to reduce multiplication of microorganism and to get low bacterial count in the milk and milk products.
2. Processing of milk using either batch pasteurizer or HTST plant requires chilled water or any other cooling medium for cooling of milk.
3. Manufacture of many products requires refrigeration such as Butter and ice-cream.
4. Storage of milk and milk products requires maintaining low temperature in cold storage depending upon type of product to be stored. Milk is stored at around 3 – 4°C while ice-cream is stored at – 30°C temperature.
5. Transportation of many products requires refrigerated vehicles to maintain quality of product.
6. Low temperature storage is required at distribution of product as well as at consumer level.