Is Shelf-Stable, Boxed Milk Bad for You?

Ever looked at the boxed milk in the grocery store and thought "huh?" Here's the deal with shelf-stable milk.

Woman Holding Glass of Milk
Photo: Getty Images / Design: Mehroz Kapadia

If you always added fresh, cold milk to your favorite childhood cereal growing up, the idea of boxed milk might seem questionable. But non-refrigerated milk, which has been pasteurized and made shelf-stable through treatment with heat, has found its way to the center aisles of grocery stores.

Wondering whether or not you should feel weirded out? Here's everything you should know about boxed milk, and how it differs from refrigerated milk.

What is boxed milk?

As mentioned, the reason that boxed, shelf-stable milk doesn't have to be refrigerated is that it's been pasteurized, unlike refrigerated milk. Pasteurization is a process that applies heat to destroy pathogens in foods (similarly to the way white blood cells destroy pathogens such as bacteria and viruses in your body), according to the International Dairy Foods Association. For refrigerated dairy products, high-temperature short-time (HTST) pasteurization involves heating every particle of milk or milk product to at least 161°F using metal plates and hot water. The milk remains at high heat for at least 15 seconds, followed by rapid cooling. It then has a shelf life of five to 15 days.

Ultra-high-temperature (UHT) pasteurization, also known as aseptic processing, involves heating milk using sterile equipment and packaging it under "aseptic conditions." Voilà! You're presented with shelf-stable milk that will help you survive should you ever find yourself invaded by aliens or stuck on a desert island and forbidden from going to Whole Foods.

Back to the whole "aseptic" thing. All aseptic operations are required to file their processes with the Food and Drug Administration (FDA). Therefore, there is no set time or temperature for aseptic processing. The FDA's "Process Authority" establishes and validates the proper time and temperature based on the equipment used and the product being processed. Basically, this non-refrigerated milk is watched more closely than any child you ever babysat.

"Dairy products that have been heat-sterilized and wrapped in sterile packaging do not require refrigeration as the sterilization prevents the milk from spoiling," says Lisa Moskovitz, R.D., C.D.N., founder of NY Nutrition Group.

What about dairy-free boxed milk?

Shelf-stable, nondairy milk products are processed the same way. Blue Diamond Almond Breeze processes its refrigerated almond milk products using standard dairy processing (HTST) and produces its shelf-stable milk products using UHT processing. The shelf-stable stuff comes in aseptic carton packaging that is "designed for shelf stability of the unopened product for an extended period," according to Blue Diamond. Silk says the same of its soy milk, almond milk, coconut milk, and cashew milk. Still, all brands suggest refrigerating milk boxes before using them. And always refrigerate shelf-stable dairy and plant-based milks after opening the package.

Is boxed milk less nutritious than the refrigerated milk?

You can count on getting nutrients from your favorite milk, boxed or otherwise. "While heating [shelf-stable milk] to high temperatures through the sterilization process can deplete some nutrients, it doesn't affect key nutrients such as protein or calcium, and is usually fortified back with many nutrients that it may have lost, including vitamins A and D," says Moskovitz.

But wait — aren't "fortified" products typically a no-no? "In this case, since the nutrients are just being added back, and not necessarily in excess of what the milk had to begin with, these fortified shelf-stable milks shouldn't pose any harm," says Moskovitz. "All in all, both versions are nutritionally equivalent."

Does boxed milk taste different?

Boxed milk flavor may vary slightly due to the heating process. Additionally, "when you finally open up the carton, it is room temperature versus cold, refrigerated milk," says Moskovitz. So have some patience and place your shelf-stable milk in the refrigerator for an hour or so before you drink it.

Now you can return to your office kitchen and snag yourself a nice cup of joe without wrinkling your nose at the "creepy" boxed milk options in front of you. It's only weird if you make it weird.

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