Milk is a staple food in many people's diets, providing carbohydrates, complete protein and a host of nutrients that other foods often lack, such as B vitamins and calcium. Pasteurization is a process of heating raw milk to a certain temperature to kill microbial, fungal and other agents that contribute to spoilage. Exposure to heat may degrade the nutritional quality of the milk slightly.
Ultra-pasteurized and pasteurized milk both heat milk to kill bacteria it may be harboring, but they heat milk to different temperatures and for different amounts of time. During standard pasteurization, manufacturers heat milk to a minimum of 161 degrees Fahrenheit for at least 15 seconds. Ultra-pasteurization heats the milk to at least 280 degrees Fahrenheit for a minimum of two seconds. The extreme heat used in ultra-pasteurization allows the milk to remain safe for consumption for up to six months if it remains unopened and stored properly.
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One issue that does arise with ultra-pasteurized milk is the denaturation of the whey protein in the milk. Registered dietitian Margaret McWilliams explains that the extra heat used in ultra-pasteurization breaks some of the structural bonds in the protein, thereby causing it to elongate. This can affect the protein's solubility and how it behaves in your body. A 2008 study published in the "Journal of Nutrition," shows that humans utilize more proteins from postmeal pasteurized or micro-filtered milk than from ultra-pasteurized milk. However, serum nitrogen levels were higher after consuming ultra-pasteurized milk, which the researchers conclude is likely the result of protein denaturation.
Adding heat to raw milk causes mild nutrient loss in pasteurized milk. The University of Minnesota reports that pasteurized milk loses 3 to 4 percent thiamin, less than 5 percent vitamin E and less than 10 percent of biotin during the heating process. Jesse Gregory III demonstrated in 1982 that the denaturation of milk's whey proteins through pasteurization can decrease how well your body absorbs the milk's vitamin B12. Ultra-pasteurization may further degrade these nutrients, though the increased shelf life of the milk often offsets the additional nutritional cost.
The U.S. Food and Drug Administration reports that raw milk can carry dangerous bacteria like Salmonella, E. coli and Listeria, all of which may pose a significant risk to your health. Pasteurization kills these harmful bacteria, though it may leave other nonpathogenic bacteria that can still cause milk spoilage. Ultra-pasteurization effectively kills all bacteria in the milk. Removal of these bacteria may alter the flavor of the milk.
- "The Journal of Nutrition"; Ultra High Temperature Treatment, but Not Pasteurization, Affects the Postprandial Kinetics of Milk Proteins in Humans; Magali Lacroix, et al.; 2008
- "The Journal of Nutrition"; Denaturation of the Folacin-Binding Protein in Pasteurized Milk Products; Jessie F. Gregory III; July 1982
- University of Minnesota; Raw Milk vs. Pasteurization Debate Revisited; Suzanne Driessen; September 2003
- U.S. Food and Drug Administration; The Dangers of Raw Milk -- Unpasteurized Milk Can Pose a Serious Health Risk; October 2006