Here's How Long Your Oat Milk Will Last After Opening
Even the best laid meal plan can result in ingredients that are used once and then abandoned in the fridge. For example, when you open a container of oat milk to use in a new smoothie recipe, you'll be left with the majority of your 32-ounce or half-gallon jug. Similarly, a daily drizzle of oat milk in your morning coffee might still leave you with sour milk before it's consumed.
Like all foods, oat milk doesn't last forever. In fact, it has a relatively short period of freshness. In general, you should plan to use up oat milk within five to 10 days after opening. If you can't use it within that time frame, consider freezing it. Note the freezing process causes the separation that makes the oat milk a bit watery and grainy when defrosted. While it might not hold over for the best drinking experience, frozen oat milk is perfectly fine for use in recipes. Before you get to that point, however, you should understand how long you have to use oat milk up once it's opened. The truth is — it varies.
How long oat milk lasts depends on a few factors
While you can make your own oat milk, you'll be skipping the preservatives and pasteurization that can keep bacteria at bay. When considering the pros and cons of making your own oat milk, take into account that you'll have to use up your freshly brewed blend within three to five days. On the other hand, if you're using a shelf-stable brand of oat milk from the store, you can likely get 10 days out of it before it begins to show signs of spoilage.
Note that some oat milks need to be refrigerated even before opening. If you got yours from the refrigerated section at the store, it probably fits into this category. Put it in the fridge as soon as you get home and note the "use by" date. Read the label further and you'll typically see a suggestion to use within five to seven or seven to 10 days after opening. Once you open the carton, consider writing the date on the outside with a permanent marker so you don't lose track of how long it's been.
Shelf stable oat milk is typically packaged in a sterile aseptic container, which is what keeps bacteria from developing during storage. This means it's also more flexible in terms of an expiration date, often six months to a year out compared to a few weeks with oat milk that requires refrigeration. However, the timeline for consumption after opening is the same.
How to tell when oat milk has spoiled
The concern about whether your oat milk is past its prime has more to do with safety than taste. While it's unpleasant to unexpectantly guzzle down sour milk, unseen pathogens can make you very sick. Avoid food-born illness from your oat milk by following standard safety protocols like never leaving opened oat milk out longer than two hours and ensuring your milk is stored in a tightly sealed container.
Although you can't see the tiny microbes that can lead to illness, there are definite signs your oat milk has gone bad. To check, pour some into a clear glass. If it looks thick or chunky, toss it out. Similarly, it should maintain a creamy white color — it turns yellow as it goes bad. Also look for mold development around the lid of the container. If it passes the visual inspection, give your oat milk a sniff. Sometimes that's all you need in order to know it's sour. If you have any doubt about the freshness of your oat milk, don't take any chances. Toss it out.