In the world of food safety, the temperature zone where bacteria can thrive is called "the danger zone" and it exists between 40 and 140 degrees F. In that temperature zone, bacteria have all they need to multiply and ultimately increase your chance of getting sick. Food can hang out in this zone for a bit, but after two hours, the risk of potentially harmful bacteria is significant. The clock rolls back to just one hour if the ambient temperature in the room is at 90 degrees F or higher — all to say, it's imperative to get that milk back in the fridge as soon as possible.
Can You Leave Butter on the Counter?
Now, you may be thinking, "but I leave dairy on the counter all the time!" Unfortunately, all it takes is a small colony of bacteria to totally ruin your day and digestive health. Food poisoning and foodborne illness are often more common than we think; the FDA estimates more than 48 million cases per year, with 128,000 of those resulting in hospitalization.
How Long Can Cow's Milk Be Left Out?
The short answer here is about two hours. However, that's not a hard and fast rule. Many other factors can affect the longevity of your milk. It's not necessarily appetizing to think about, but all of our food is teeming with microbes. Some are beneficial (like bacteria that aid in digestion), while others are dangerous (like the kind that causes foodborne illnesses). Dairy items are particularly hazardous to leave out because certain harmful bacteria love dairy best. Four of the major culprits are E. coli, Salmonella, Campylobacter, and Listeria. All of these strains can lead to extreme food poisoning symptoms that can be very serious and, in some cases, require hospitalization.
Another factor is whether the milk container has been opened yet or not. Manufacturers take extra precautions to ensure that the container and the milk itself are as clean as possible. While it's not possible to completely remove all bacteria from the interior and exterior of a container of milk, keeping it sealed keeps that amount as low as possible. Once the seal is broken, more and more bacteria sneak in — some of which can be dangerous. Keeping the milk cold makes sure those dangerous bacteria don't have the opportunity to multiply into amounts that will make you sick. A quick tip about storage: Never store milk in the refrigerator door, that's the warmest spot in your fridge and can make your milk go bad faster.
Lactococci and lactobacilli are two strains of bacteria often found in dairy. They convert the natural sugars found in milk into lactic acid, and anyone who has added lemon or vinegar to milk knows (i.e. made buttermilk), acid causes milk to curdle. Both lactococci and lactobacilli begin to multiply exceptionally rapidly in the danger zone, accelerating the natural spoilage process that occurs in dairy. The byproduct of this conversion process is a very pungent smell that we all associate with spoiled milk. Ironically, in a controlled setting, these bacteria are used to curdle milk intentionally to make cheese and other probiotic products.
How Does Milk Become Cheese?
Does Almond Milk Go Bad If Left Out?
Just like dairy milk, almond milk can go bad if left out. Again, the general rule of about two hours applies but the signs of spoilage and outcome can differ. Many times, almond milk is sold in rectangular, cardboard containers that are shelf-stable until opened. This may make it seem like it can be stored in the pantry, but once opened, these containers must be stored in the refrigerator. This, of course, goes for cartons of almond milk sold from the refrigerated section as well. Unlike dairy milk, it isn't immediately apparent when almond milk has spoiled. There isn't that distinct rotten milk smell to alert you that something isn't right. Particularly with the shelf-stable cartons, a good visual cue is the condition of the carton itself. If it's distended or bloated in any way, that's a sign of excess gas production that occurs during the spoilage process, and it's time to throw it out. Any texture change, especially slimy or clumpy bits, is a surefire sign that almond milk has gone bad. Fewer types of harmful bacteria are found in almond milk than in dairy milk, but the risk is still there, especially for Campylobacter and E. coli.
Does Oat Milk Go Bad If Left Out?
Oat milk tends to have a shorter shelf life than other non-dairy milks, even when stored safely. This means the spoilage process may already be in motion once you leave oat milk out for a bit. Some oat milk brands start to deteriorate after just four days opened in the fridge. In the danger zone, bacteria can double in only 20 minutes, so if there's already a higher amount present, that number can become dangerous really fast. Like all other refrigerated food, it's best to stick to the two-hour rule. And when in doubt, throw it out.
Related:
- What Is Sour Milk — and Is It Safe to Use?
- Can You Freeze Milk?
- The Dos and Don'ts of Heating Dairy Products
