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FAQ - Pasteurization

Last Updated: May 17, 2012
Q. Is pasteurization required by law?
A. Since 1938, the Ontario Health Act has required pasteurization of all milk and cream for human consumption. It is illegal to sell or even give away milk, cream or milk products that have not been pasteurized in a plant licensed under the Milk Act. Pasteurization destroys pathogens, such as salmonella and E. coli, that can cause human illness. It has been used extensively as an effective and efficient method of preventing transmission of foodborne illness to consumers via milk and milk products.
Q. What is pasteurization?
A. In general terms, pasteurization is the process of heating a food, usually a liquid, to a specific temperature for a definite period of time, then cooling it immediately.
Pasteurization is the main reason for milk’s extended shelf life. It has been one of the most beneficial and cost-effective measures to protect the health of the consumer.

Dairy processing plants use three methods to pasteurize milk:

1. High Temperature Short Time (HTST) Method

  • milk is pumped rapidly through a series of steel plates
  • milk is heated to 72°C and held no less than 16 seconds
  • then it is rapidly cooled to 4°C
  • a continuous-flow pasteurizer is used to achieve this precise temperature control
2. Batch-Holding Method
  • uses a paddle or coil in a large vat to agitate the entire batch of milk as it heats to62°C
  • the milk is held at this temperature for 30 minutes before being cooled to 4°C
3. Ultra High Temperature (UHT)
  • whole or partly skimmed milk is heated to 138°C - 158°C for one or two seconds
  • milk is quickly cooled and placed, under sterile conditions, into pre-sterilized containers
  • an unopened package of UHT milk will keep for three months with very little change in flavour and quality
  • once opened, milk should be refrigerated and used within one week
Q. What about milk's nutrients?
A. Pasteurized milk is an excellent source of calcium, protein, riboflavin, vitamins A and D, phosphorous, and a good source of thiamin and B12. Studies have shown that calcium absorption remains unaltered through pasteurization. Vitamins A and D, as well as riboflavin and niacin are generally not affected by heat treatment. Pasteurization does involve a minor loss of 10 per cent of thiamin and vitamin B12 content, as well as a 20 per cent loss of vitamin C content. Because losses are small, in comparison to the large amount of these two B vitamins present, milk continues to provide significant amounts of thiamin and vitamin B12. As milk is not an important dietary source of vitamin C, this loss is not nutritionally significant. All processed milk sold in Ontario is of high quality, contains no preservatives and is backed by stringent government and quality control programs and standards from the farm to the retail shelf.


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