And how you know when it's gone bad
While I know that dairy products have a limited shelf-life, I've deluded myself into thinking that nondairy milks, like almond milk, can last in my fridge an exponentially longer amount of time. That, however, couldn't be further from the truth. Almond milk can go bad, develop a rancid odor, and coagulate into little white clumps. So what is the shelf-life of almond milk?
In a nutshell, the shelf-life of almond milk really depends on what type of almond milk you're buying and how it's packaged and stored. If you're getting almond milk from the refrigerated section of your supermarket, you need to store that almond milk in your refrigerator at home. The shelf-life of that unopened almond milk varies from brand to brand; the shelf-life of almond milk from the New Barn is 90 days in the fridge. The best-by date will be listed on the side of the bottle.
Once opened, however, that same almond milk will only last about seven to ten days, according to the folks at the New Barn, and it should be kept in the fridge. That window of freshness—between seven to ten days after opening—holds true for almond milk from Califia Farms, too. They claim, "It is not unusual for our products to remain good past the 10-day mark," but they won't guarantee it.
You can also get shelf-stable almond milk, like that from Pacific Foods, which is pasteurized at ultra-high heat in metal-lined boxes called Tetra Paks. According to the company's FAQ section, these unopened boxes of almond milk can be stored at room temperature for about a year, if not a little longer. After all, the manufacturers note that the nut beverage is probably good for up to "six months after the best if used by date" that's listed on the box. However, once you open the box of almond milk by breaking open the seal, you should still refrigerate it and use it up in seven to ten days, just as you would the non-shelf-stable almond milk—ideally in the coldest part of your fridge, not the fridge doors.
If you opened your bottle of almond milk about a week ago and want to confirm if it's still good to drink, the best thing to do is to smell it. As Carolyn Flood, co-founder of NotMilk, told Epicurious, other signs almond milk has gone bad include a sour taste, a thicker texture, and a weird smell. If the almond milk has separated, it's not spoiled; that's a natural thing that happens with almond milk. But if you see clumps, dump it out and open a new bottle. Or, if you're feeling adventurous, make your own almond milk. At least you'll know for sure it's fresh.