How to Tell If Oat Milk Is Bad

If you've gotten into putting oat milk in your coffee, pouring it over your cereal or baking with it, you're not alone. Sales of plant-based milks have been growing worldwide, and research from Fairfield Market Research indicates that the demand for it is going to keep growing over the next few years at least.

If you need or prefer to avoid cow's milk, oat milk can be a healthy and eco-friendly nondairy option. Or maybe you just like oat milk's mild, slightly sweet flavor, which is particularly nice in lattes and pudding. Whatever your reason for buying oat milk, you're going to want to store it properly—and know when it's gone bad and it's time to toss it.

Related: The 5 Best Oat Milks

How Long Can Oat Milk Last in the Fridge?

If you bought your oat milk in the refrigerator section of the grocery store, put it in your fridge as soon as you get home. (Your fridge should be set below 40° F.)  Like most other foods and drinks that need to be refrigerated, oat milk shouldn't be left at room temperature for more than two hours.

When it comes to how long any individual container of oat milk will last in the fridge, a Food and Drug Administration spokesperson told EatingWell that the organization recommends that consumers follow the labels regarding expiration dates and shelf life of the product. But those labels can read like a bit of a riddle. Here's how to understand them:

• "Sell-by" dates are aimed more at the retailer than the consumer, letting them know when a product should be off the shelves. Your oat milk (and other products) should still be good for several days after this date.

• "Best if used by/best before" dates are an indicator of quality. The product might not taste as good after this date or the texture might suffer but it should not be bad or make you sick if you consume it after this date.

• "Use-by" dates indicate the last day the manufacturer recommends using the product based on quality, not safety. (The exception to this is infant formula, which should not be used after use-by dates.)

Oat milk should also have a note on the label about how long it can be stored in the fridge once opened. Most should last from 7 to 10 days, but check the label to be sure.

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How Long Does Shelf-Stable Oat Milk Last?

Just like with oat milk you bought in the refrigerated section, shelf-stable oat milk should have a label that indicates how long it should last both before and after opening. Unopened, most shelf-stable oat milks should last for at least six months in your pantry or a cabinet. Just avoid storing the oat milk in a place that gets very hot or cold, like your garage. "The best way to store these products is in ambient temperatures, generally lower than 85ºF, and out of direct exposure to sunlight," says Cynthia James, M.S.F.S., an extension support specialist with the Cornell Food Venture Center.

Once opened, shelf-stable oat milk is no longer shelf-stable and should be stored in the fridge. There should be a note on the label indicating how long it should last in the refrigerator after opening—this should generally be a week to 10 days.

What About Homemade Oat Milk?

Making your own oat milk is easy, but homemade oat milk generally doesn't last as long as store-bought. James says a realistic estimate is three to five days in the fridge.

How to Tell If Oat Milk Is Bad

"The best way to tell if oat milk has gone bad is to smell and look at the milk," says Janice Revel, co-founder of StillTasty.com, a website that helps readers avoid food waste with its vast database of information about the shelf life of different foods. "Signs of bad oat milk are a sour smell, a yellowish tinge to the color and a clumpy or thick texture." If you smell or see any of these signs, it's time to toss the oat milk even if it hasn't reached its best-by date.

If you're risk averse, your best bet is to follow the dates on your oat milk labels closely, since, as both the FDA and James from Cornell note, not all foodborne pathogens affect the appearance, smell or taste of foods and drinks. "I would not recommend consuming the product past its 'use by' date," says James. "Microbial pathogens and their toxins that can make us the most sick are often not detectable by sight, taste or smell.  Don't risk it, it's not worth it."

Can You Freeze Oat Milk?

You can absolutely freeze oat milk, but freezing can affect its texture so it's best to freeze oat milk you plan on using in recipes rather than drinking straight-up. "Frozen oat milk will often become separated, and the texture may become somewhat grainy when thawed," says Revel. "If you're using the oat milk for cooking, this usually won't be noticeable. Just give the thawed oat milk a good shake or stir before using to deal with any separation. If you're planning to drink the oat milk, on the other hand, you may not like the texture once it has thawed. One tip is to test-freeze a small amount, thaw it and see how you like the outcome."

To freeze oat milk, transfer it to a freezer-safe airtight container, being sure to leave at least a half-inch of headspace at the top of the container since the oat milk will expand when frozen, says Revel. You can also freeze oat milk in ice cube trays and then transfer the cubes to a freezer bag if you want to have smaller portions to thaw later. "Properly stored, frozen oat milk will maintain best quality for about four months, but will remain safe indefinitely," Revel says. Transfer the oat milk to the fridge to thaw, and stir or shake it well before using.

Keep an eye on those expiration dates, and as they get close just go ahead and freeze it and you'll never have to wonder if your oat milk is bad again.

Bottom Line

Oat milk is a popular nondairy beverage you can use for smoothies, baking or simply drinking as is. Whether you buy refrigerated or shelf-stable oat milk, you'll want to store it properly to ensure it stays fresh. Once opened, you can typically refrigerate oat milk for about a week, but following the instructions on the packaging is your safest bet. Dispose of any oat milk that's developed a sour odor, yellowish tinge or chunky texture.