Frequently Asked Questions
By Althea Zanecosky, MS, RD, LDN
Mid-Atlantic Dairy Association
January 2008
Q: When I made pudding using raw milk, my dessert separated and looked and smelled unappetizing. What happened?
A: There are two major processes that differentiate raw milk and pasteurized milk. Most milk undergoes a heat treatment, known as pasteurization, which kills bacteria, and homogenization, which distributes the fat evenly among the product.
Pasteurization destroys a small number of milk enzymes but most of the natural enzymes in milk survive this process. However, the enzymes that are naturally present in milk are bovine enzymes which our bodies don't use. Enzymes in the food that we eat and drink are broken down in our digestive tract; human bodies rely on human enzymes to digest and metabolize food and to regulate body processes.
Milk secreted from the udder of a healthy cow contains some bacteria. These bacteria produce enzymes, which are proteins that speed up the rate of chemical reactions. The enzymes that negatively affect products made from milk are those that bring about undesirable changes in proteins (proteases) and fat (lipases). Some bacterial enzymes can be inactivated by the heat from the pasteurization process. Enzyme activity in raw milk – which is not pasteurized or homogenized - can have negative effects like the one that occurred in your pudding.
The protease enzyme causes protein destabilization, which results in whey separation and can leave a curdled appearance. The slightest protease activity can produce “off” flavors. Another enzyme, lipase, also found in raw milk, causes the release of small building blocks of fat called fatty acids. Fatty acids produce a flavor that is desirable in some cheeses but not in dairy desserts like pudding and ice cream. Homogenization increases the exposure of the fat in milk fat to lipase, preventing off flavors.
Raw milk advocates claim that unprocessed milk is healthier because pasteurization destroys enzymes, bacteria, and nutrients found in milk. However, current research shows that there is no significant difference in the nutritional value of pasteurized and unpasteurized milk. The major nutrients like calcium and potassium are left unchanged by pasteurization. The family of milk proteins, including casein and whey, are also largely unaffected. Milk is a good source of the vitamins thiamine, folate, B-12 and riboflavin and pasteurization results in losses of anywhere from 0 to 10 percent for each of these (which scientists consider only a marginal reduction). Vitamin D, which enhances the body's absorption of calcium, is added to processed milk and is not found in raw milk.
Federal law requires pasteurized milk in commercial dairy products and for good reason. Barns are not sterile environments. Cows can pick up pathogens, which can then be transmitted to milk during transportation or processing. By heating milk to 161 degrees Fahrenheit for 15 seconds, a process used since the early 1900s, harmful bacteria like Campylobacter, Escherichia, Listeria, Yersinia, Salmonella, and Brucella are killed.
The American Medical Association, the Food and Drug Administration, the Centers for Disease Control and the American Academy of Pediatrics have released position statements endorsing the use of pasteurized milk and affirming the health risks associated with unpasteurized milk.
For other information about raw milk and pasteurization visit the U.S. Food and Drug Administration at:
http://www.cfsan.fda.gov/~dms/rawmilk.html