Why Does Organic Milk Last So Long?

If you’ve switched from regular to organic milk, one thing you might have noticed is that it lasts a long time in the fridge. While you might attribute its longevity to the organic bit, that’s not quite it.

Years ago, when we started buying organic milk, I noticed that it lasted forever. I can’t remember the last time I opened a container of organic milk, and it smelled off. But when buying regular milk, it often seemed to go off within days of purchasing it despite how quickly my family goes through milk.

It turns out that despite my initial belief, it has absolutely nothing to do with the milk being organic and everything to do with the way the milk is prepared for packing and shipping.

The milk you’ve been drinking and buying for most of your life is pasteurized to kill off bacteria—shout out to my boy Louis Pasteur because not dying of botulism is awesome. The standard industry practice is the low-and-slow approach to pasteurization; the milk is heated to 161° F for 15 seconds to kill a high percentage of the bacteria in the milk. Organic milk producers use a process that is more of a high-and-fast approach to pasteurization called ultrapasteurization. The milk is raised to 280° F for only 2 seconds, but it kills off even more bacteria than the slower pasteurization process favored by traditional dairies.

While the organic milk dairies may do this as an extra precaution when dealing with milk produced by cows that aren’t fed the usual battery of antibiotics, it’s probably for a much more pragmatic reason.

Organic milk is shipped farther than regular milk (as organic dairies are fewer and farther between than regular dairies) and ultrapasteurized milk simply lasts longer in transport, on the shelf, and in your fridge. Milk pasteurized the low-and-slow way can last up to 2 weeks if unopened and kept cold enough, but the ultrapasteurized counterpart can make it up to 60 days under the same conditions.

So the next time you open the last carton of organic milk in that big ol’ Costco three-pack you’ve been buying and think “How on earth is this still so fresh?” you can thank ultrapasteurization for ensuring you’ve got all the milk you crave, fresh and when you want it.