This milk can last for months in your fridge—is that a good thing? 
Credit: Photo: Greg Dupree

You’ve likely seen those cartons of milk in the dairy aisle with crazy-long expiration dates—we’re talking in the realm of months. What makes them so stable and long-lasting? It’s not because of additives or preservatives, it’s because of heat. Here’s the breakdown on the difference between the jugs of milk that expire in a snap, and the ones that you’re allowed to forget about in the back of your fridge.

Pasteurized Milk

This is the basic stuff: You know when you buy a gallon of this, it needs to be gone by the end of the week, no exceptions. Normally, pasteurized milk has been heated to 161°F for 15 seconds or 145°F for 30 minutes. This kills most of the harmful bacteria that could make you sick, according to Cornell University's Department of Food Sciences. The equipment it’s processed on is carefully sanitized, but it’s still exposed. Any bacteria that may have survived this process is kept tame when refrigerated (below 45°F, which your fridge at home should definitely be well below) and won’t cause your milk to spoil within the span of the usual use-by date. We probably don’t need to tell you twice, but this milk needs to be used up as soon as possible after opening if you’re looking for the best taste and freshness.

Ultra-Pasteurized Milk

The main difference between Ultra-Pasteurized and normally pasteurized milk is the temperature it’s heated to. It’s heated to 280°F at the minimum, which means that it’s able to kill almost all of the bacteria that the normal pasteurization process may have missed (Keyword here being almost—it’s not sterile.). The equipment it’s processed on is typically sterilized and sealed, though. Ultra-Pasteurized milk’s flavor is a little different from normally pasteurized milk because of the high heat it’s held at, but it’s great to have on-hand if you only keep milk around for an occasional splash in your coffee or tea. Here’s the caveat: Those crazy 30-90 day expiration dates are only until you open the carton. After that, you still need to finish it up within about a week or 10 days.

Is there a difference?

According to the FDA, the process of pasteurization doesn’t affect the nutritional value of milk. And if you find yourself regularly throwing out milk week after week because it’s gone bad, Ultra-Pasteurized milk may be a good purchase to save on money and food waste. It does taste a little more “cooked” because of the heat treatment, so if you’re looking to glug down a whole glass of cold milk with your cookies, it may taste different to you on first try. But for the occasional splash in your morning coffee, to thicken sauces, or just have on hand in case of emergencies if you’re not a huge milk person, Ultra-Pasteurized is a great alternative.