All milk that is sold through the dairy industries in the United States and Canada is pasteurized to eliminate harmful contaminants. Ultra-high temperature treatment is a newer process that also sterilizes milk. This treatment extends the shelf life of milk up to six months or more without refrigeration. However, this longer expiration date does come with some disadvantages.
How It Works
Pasteurization is a treatment that destroys potentially harmful bacteria in milk. Typical pasteurization is accomplished by heating milk to 63 °C for 30 minutes or at 71 °C for 15 seconds. Although the most dangerous pathogens are eliminated by this treatment, some types of bacteria remain. These are the bacteria that cause milk to spoil. Ultra-high temperature treatment kills off these bacteria, in addition to the dangerous forms. For ultra-high temperature treatment, the milk is heated to 140 °C for one to two seconds.
Vitamin C
Vitamin C, also known as ascorbic acid, is an important antioxidant compound in the body. It plays key roles in growth and development, wound healing and repair of tissues. It is also essential for the production of collagen protein, a major connective tissue component. Ultra-high temperature treated milk has lower levels of vitamin C compared with conventionally pasteurized milk.
Folic Acid
Folic acid is a B-complex vitamin that your body needs to produce new cells. It is critical during pregnancy for the earliest stages of embryonic development and deficiencies may cause birth defects. The milk proteins that bind folic acid become partially denatured or broken down at the high temperatures used to produce ultra-high-temperature-treated milk. The bioavailability of folic acid in ultra-high-temperature-treated milk is much lower than that of pasteurized milk.
Flavor
A well-known problem in the production of ultra-high temperature treated milk is the flavor quality. This problem occurs when the ultra-high temperature treatment is not completed quickly. Some methods for heating the milk take several seconds to reach the target temperature of 140°C. The milk must reach that temperature and instantaneously cool down. If the milk remains at a high temperature for too long, the milk will taste burned.
References
- "Southeast Asian Journal of Tropical Medicine and Public Health", Loss of L-ascorbic Acid in Commercial Drinking Milk Caused by Milk Processing and Storage Times.
- "European Journal of Clinical Nutrition", Bioavailability of Folic Acid from Fortified Pasteurised and UHT-treated Milk in Humans.
- American Chemical Society: Chemical & Engineering News
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