Here’s How Long That Carton of Oat Milk *Actually* Stays Good For, According to a Food Scientist

Photo: Stocksy/Nadine Greeff
Creamy, fully foam-able, and rich in protein, oat milk—a plant-based milk made by soaking oats in water—has deservedly become one of the most popular alternatives to dairy milk. (And in addition to being widely available, it’s easy to make at home with just a few ingredients.)

Here's the thing, though: Even though it’s not a dairy product, know that oat milk can still go bad fairly quickly. So just like you would with regular ol’ cow’s milk, you want to make sure your carton of oat milk is *not* spoiled before you drown your precious granola in it or pour it into your morning matcha latte. Here's how long you should be storing your oat milk before it spoils, plus a food scientist's recommendations for keeping it fresh for as long as possible.

Experts In This Article

How long does oat milk last?

According to London-based food scientist Natalie Alibrandi, CEO of Nali Consulting, once the container has been opened, store-bought oat milk typically remains good for about seven to 10 days in the refrigerator.

There are factors that can reduce the shelf life of oat milk, however—like leaving the opened container at room temperature for more than a few minutes at a time, for example, especially on a warm summer day. “As soon as you are done using the milk, put the cap back on and return it to the fridge,” Alibrandi says. “And whatever you do, don’t leave your oat milk out on the counter uncapped for several hours of time—or, ideally, any span at all—as you will quickly reduce its perishability limit.”

The main concern with oat milk, Alibrandi explains, is mold growth that can make you ill if you ingest it. While some brands of oat milk are produced in aseptic cartons and can last for as long as year at room temperature when unopened, Alibrandi explains that you should always follow the “best by date” on the carton for best result—and keep the carton in the fridge if the packaging advises doing so. Once you open the carton, your seven to 10 days starts. “The actual milk is typically completely sterile before it has been opened,” says Alibrandi. “Therefore, the only exposure to other microbes is through the air once the product is opened.”

So, how can you tell that it’s time to cut your losses and toss that carton of oat milk sitting around in the fridge for more than a week? Changes in the texture of the oat milk—if it becomes thick and chunky, for example—are signs that it has gone bad and should be discarded, Alibrandi says, adding that you should also pay attention to the color and smell of the milk.

“If the color changes drastically from when the carton was initially opened, I would recommend smelling the product to see if it smells sour,” says Alibrandi. “If you can’t determine if the smell is sour, then take a small sample and sip it to see if the flavor has changed much from what it initially tasted like. If the flavor is sour, or has a sour aftertaste, you should discard the milk before consuming any more.”

How to make your alt milk last longer

Oat milk should be stored at a temperature of 40°F, says Alibrandi. To extend the shelf life of oat milk, she recommends storing the container on the lower shelves of the refrigerator rather than on the door, which she notes is the warmest part of any fridge. Alibrandi also says that different brands and varieties of oat milk (“barista” oat milk, for example, is has a higher fat content than regular oat milk and is therefore considered better for steaming and foaming) may each have slightly different guidelines with regards to proper storage and shelf life, and that it’s always best to adhere to the instructions on the packaging.

“You should not see a huge difference in perishability between different types of oat milk, original vs. barista for instance,” says Alibrandi. “But still follow the rules, as different products will have different formulations which affect shelf life.”

Up next: Settling the oat milk vs. almond milk debate once and for all.

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