Does organic milk have a longer shelf life than regular milk?
Most regular, nonorganic milk has been pasteurized according to a high-temperature, short-time process (HTST) where the milk is heated to 160 degrees for 15 seconds, killing virtually all bacteria and prolonging shelf life to about two weeks in an unopened carton or 10 days opened. Most organic milk, on the other hand, has been ultra-pasteurized with an ultra-high temperature method (UHT), the same method used to pasteurize milk packaged in aseptic cartons, such as Parmalat: The milk is heated to 280 degrees for two to four seconds, killing all bacteria and giving it an even longer shelf life (about one month unopened or two weeks opened). Because organic milk producers are still relatively few and far from distribution centers, most use UHT to allow for longer distances traveled.
The downside to ultra-pasteurized milk? Its taste. When our tasters sipped ultra-pasteurized organic milk alongside regular pasteurized milk, they found it had a slightly “cooked” flavor, while pasteurized milk tasted “rich” and “full-bodied.” Our advice: Though it can be difficult to locate, if you find pasteurized (rather than ultra-pasteurized) organic milk, buy it.