Why does oat milk only last 7 days after opening?

Oat milk has become an increasingly popular plant-based milk alternative in recent years. With its creamy texture and mild, pleasant flavor, many people have made the switch from dairy to oat milk. However, one downside to oat milk is its relatively short shelf life after opening. An unopened carton of oat milk can last 5-10 days past its printed expiration date when stored properly. But once opened, oat milk only lasts about 7 days in the refrigerator before going bad.

The Shelf Life of Unopened vs Opened Oat Milk

The reason oat milk has a longer shelf life unopened versus opened comes down to exposure to oxygen. When the carton or bottle remains sealed, the oat milk inside has minimal exposure to oxygen. Exposure to oxygen is one of the main factors that causes food and beverages to spoil over time. Once the container is opened, the oat milk is exposed to more oxygen both from the air in the refrigerator and from each time it is poured out. This oxidation causes the quality and freshness of the oat milk to degrade faster.

Oat Milk Type	Shelf Life
Unopened	5-10 days past printed expiration date
After Opening	7 days

As you can see from the table, an unopened oat milk can last much longer, generally 5-10 days past any expiration date printed on the packaging when stored properly. However, once exposed to air, its shelf life drops to just about 7 days in the refrigerator.

Why Oat Milk Spoils Faster Than Other Milk Alternatives

Another question that often comes up is why oat milk tends to have a shorter shelf life after opening compared to other plant-based milk alternatives like almond milk or soy milk. There are a few reasons for this:

• Higher water content – Oat milk has a higher water content than other plant milks. Foods with more moisture spoil faster.
• Natural sugars – Oat milk also contains more natural sugars from the oats, which can aid spoilage.
• Lack of preservatives – Many oat milk brands do not use artificial preservatives to prolong shelf life.
• Not UHT treated – Most oat milks are pasteurized but not ultra-pasteurized using UHT. UHT treatment allows longer shelf life.
• Higher pH – The pH of oat milk is near neutral compared to the lower pH of soy or almond milk. Higher pH shortens shelf life.

So while oat milk provides great flavor and nutrition, its composition and lack of processing means it does tend to spoil faster after opening compared to other plant-based milk options. Proper storage is key for maximizing its shelf life once opened.

How to Tell If Opened Oat Milk Has Gone Bad

Being able to identify the signs of spoiled oat milk can help avoid accidentally consuming milk that is past its prime. Here are a few ways to tell if your opened oat milk has gone bad:

• Change in color: Fresh oat milk is creamy white in color. As it starts to spoil, it may turn slightly gray, yellow, or develop a brown tint.
• Sour smell: Oat milk that has soured or is rotten will have a distinct sour odor.
• Curdling: Bad oat milk may look curdled or lumpy instead of smooth and creamy.
• Mold growth: Mold spots or fuzzy growth around the bottle cap are a sign oat milk has spoiled.
• Off tastes: Sip a small amount of the oat milk and taste for sour, bitter, or otherwise “off” flavors.

Trust your senses – if the oat milk smells, looks or tastes unpleasant in any way compared to a fresh sample, it is likely past its prime and should be discarded.

Proper Storage to Maximize Opened Oat Milk Shelf Life

To get the most days of use after opening a carton of oat milk, be sure to store it properly. Here are some tips for storing opened oat milk:

• Refrigerate after opening – Keep oat milk chilled at 40°F (4°C) or below.
• Seal the container tightly after each use.
• Store in the back of the fridge furthest from the door.
• Finish within 7 days and don’t exceed 1 week after opening.
• Keep the bottle clean when pouring to avoid introducing bacteria.
• Do not return unused milk back to the original container.
• Check for signs of spoilage periodically.

A good rule of thumb is to write the open date on the oat milk container so you know exactly how long it has been open. This can help prevent accidentally consuming spoiled milk that is past the recommended 7 day window.

Can You Freeze Oat Milk to Extend Its Shelf Life?

Freezing is an option for extending the shelf life of oat milk by several months. To freeze oat milk:

• Make sure the milk is fresh and recently opened.
• Pour into a freezer-safe container, leaving headspace to allow for expansion.
• Seal tightly.
• Label with the open date and freeze.
• For best quality, use within 3-4 months.

The freezing process will generally not affect the taste or nutrition of oat milk too much. Make sure to shake or stir well after thawing as separation can occur. To thaw, place sealed container in the refrigerator overnight or run under cool water briefly until reaching desired temperature.

Tips for Using Up Oat Milk Before It Expires

If you find yourself with an opened carton of oat milk nearing the 7 day mark, there are some easy ways to use it up quickly:

• Pour into smoothies, protein shakes, or blended coffee drinks.
• Use for overnight oats, cold cereal, or granola.
• Make oatmeal, chia pudding, or oat-based desserts.
• Add to pancake or waffle batter.
• Mix into creamy soups, risottos, or pasta dishes.
• Stir into curry dishes, masala sauces, or coconut milk curries.

Getting creative with recipes and Beverages is a great way to use up oat milk while it’s still fresh and avoid waste. With some planning, you can easily polish off that carton before the 7 days is up.

Does Oat Milk Last Longer in Other Types of Packaging?

You may notice that some brands of oat milk come in different types of packaging besides traditional cartons or bottles. In particular, shelf-stable oat milk that comes in aseptic cartons or Tetra Pak packaging tends to have a longer unopened shelf life. For example, Pacific Foods makes a shelf-stable oat milk that lasts for about 12-14 months unopened and 14 days after opening when stored properly.

The aseptic packaging undergoes a higher heat pasteurization process called UHT (ultra-high temperature) that better sterilizes the contents and removes more oxygen. This allows the oat milk to be shelf-stable at room temperature until opened. Other milk alternatives like soy milk and almond milk also come in this kind of long-life packaging.

Once opened, however, the shelf life of aseptic boxed oat milk is still roughly 7-14 days. So while the unopened life is extended, proper storage after opening is still important.

The Bottom Line

Understanding the relatively short shelf life of oat milk once opened can help you optimize use of each carton and minimize waste. By properly storing oat milk in the refrigerator, being vigilant about signs of spoilage, and finding creative ways to use it up within 7 days of opening, you can enjoy all the benefits of this tasty plant-based milk while keeping it safe and fresh.