How Long Can Milk Sit Out Without Spoiling? Safety Guidelines

When I was growing up in Australia, leaving the milk out on the bench was a no-no. But how long can milk actually sit out without going bad or making anyone sick?

Authorities such as the US Dairy, the CDC, and USDA’s Food Safety and Inspection Service all offer the same recommendation: don’t leave milk out of the refrigerator for more than two hours, max, at room temperature. I’m definitely thankful that I was raised with the habit of putting milk in the fridge straight away! 

But the world is full of milks – from full cream to skim, pasteurized, ultra-pasteurized and even plant based milks. Does the two hour rule apply to all of them?

In this article we’re going to look at the different shelf lives of different kinds of milk, plus:

On a really hot day, when the temps are above 90°F, cut that time down to one hour maximum out of the fridge – because bacteria that could cause food poisoning grows fastest at very warm temperatures. Remember, milk in a carton could be exposed to very high temperatures even on a moderately warm day if it’s left in your car in the sun!

As the CDC says, “Bacteria in milk can multiply rapidly if left at room temperature or in the “Danger Zone” between 40°F and 140°F.”

Raw Milk vs Pasteurized Milk vs. Ultra-Pasteurized

But wait – you might say – my milk is pasteurized! Doesn’t that mean it’s free from bacteria?

Well, unfortunately, no. According to this pamphlet from Cornell University, “some survival” of bacteria is possible in pasteurized milk. Also, regular pasteurized milk usually isn’t bottled in a sterile environment, so some recontamination can occur. 

And once you open that milk jug, all kinds of molds and bacteria from the air in your home could make their way into the milk. Added to the small amount of bacteria that may have survived the pasteurization process, these bacteria can multiply quickly to harmful levels if left out in a warm room.

Raw Milk

Raw milk naturally contains so much bacteria that the official US website Foodsafety.gov calls it “one of the riskiest” foods to consume. Standard pasteurization heats milk to 161°F for 15 seconds, killing 99-100% of pathogenic bacteria. 

That’s why pretty much every food authority agrees on one thing: Don’t consume raw milk or raw milk products. Always buy pasteurized milk. 

Ultra Pasteurized or UHT Milk

Ultra-Pasteurized milk, on the other hand, is heated to a hotter-than-boiling temperature of 275°F, although for a shorter time than regular pasteurized milk, then rapidly cooled. This gives it a longer shelf life. If you’ve ever noticed that organic milk is almost always ultra-pasteurized, it’s because it doesn’t sell as quickly as regular milk. It takes advantage of the longer shelf life to maximize sales. 

UHT milk, or Ultra High-Temperature milk, is heated to 275°F – 280°F for longer than ultra-pasteurized milk, making it essentially sterile. UHT milk is shelf-stable when packed in a sanitary facility. 

Does Milk Left Out of the Fridge Turn to Yogurt? 

Milk naturally contains some bacteria that convert lactose (milk sugar) into lactic acid. While this is the basic process for making yogurt, it’s not quite that simple in practice. You don’t know which bacteria are going to multiply fastest if you leave milk out on the counter – and, since it’s not a controlled environment, it would likely be the ones that would make you sick.

Yogurt is made by adding specific bacterial cultures, usually Lactobacillus bulgaricus and Streptococcus thermophilus, to milk. These bacteria consume the lactose (milk sugar) in the milk and produce lactic acid, which thickens the milk and gives yogurt its characteristic tangy flavor and creamy texture. This process occurs at a controlled temperature, typically around 110°F (43°C), and it usually takes several hours to complete.

Leaving milk out of the fridge at room temperature for an extended period of time will not turn it into edible yogurt. Instead, it will cause the milk to spoil and potentially become unsafe to consume. Bacteria and other microorganisms present in the environment can multiply in the milk, leading to spoilage, souring, and an unpleasant odor.

If you want to make yogurt at home, you’ll need to follow a specific process that involves introducing the right bacterial cultures and maintaining the proper temperature. Simply leaving milk out on the counter will not result in yogurt production and is not a safe practice.

Sour Milk or Spoiled Milk – Is There a Difference?

Sour milk usually refers to raw milk that has started to ferment. Spoiled milk usually refers to pasteurized milk that has gone bad. 

What happens if you drink sour milk?

If your milk tastes sour it is due to prolific bacteria growth starting the fermentation process. 

Medical News Today says “consuming a small amount [of sour milk] can cause no symptoms or some minor symptoms which go away on their own.” But it is best to avoid the risk of stomach cramps and diarrhea and just throw it out. 

How long does milk last in the fridge?

The USDA says milk lasts refrigerated for seven to ten days. It should be consumed within seven days for best flavor. Buttermilk will last up to two weeks. 

If you have to travel and just bought fresh milk, don’t throw it out! Both milk and buttermilk may be frozen for about three months, so just pop it in the freezer.

Is it okay to use expired milk?

Milk expiration dates, use-by dates, or best-by dates are meant as a guide.

If the carton has been kept below 40°F (4°C) at all times and remains unopened then you may be able to use it past the expiry date by up to three days.

If the carton has been opened, you should probably toss it. If it hasn’t, smell the milk and pour a little first. If it smells funky, looks lumpy, or chunky, throw it out. 

Can You Let Shelf Stable Milk Sit Out?

Ultra-pasteurized milk is sold in shelf-stable cartons with extended expiration dates. However, once opened it should be refrigerated and treated the same as regular milk.

Do not leave a glass or an opened carton of “shelf-stable” or ultra pasteurized milk out for longer than two hours. 

Different Kinds of Milks Have Different Shelf Lives.

Whole milk, half and half, or skim. The fat content of milk affects its shelf life. Even though this is the case, all fresh milks are best consumed within 7 days.

Plant milks last a little longer at 7-10 days. Ultra-pasteurized (UHT) milk lasts the longest. If the carton remains unopened; the shelf life can be months. 

Although plant milks have a longer shelf life, the two hour rule still applies once opened. They do however stay fresher for longer than animal milks but for optimal freshness and taste they should be enjoyed within seven to ten days.

Here’s a quick look at the shelf life of opened and unopened milk cartons: fill in the table

Conclusion 

The bottom line is you should consume all types of fresh cow’s or goat’s milk within 7 days of purchase. Consume all plant milks (soy, oat, rice, almond) within 7-10 days of opening for optimal taste and freshness. 

But remember that this time will reduce to half (3-5 days) if the milk has been left out of the fridge for over two hours at room temperature of 40°F-90°F (4°C-32°C). If it’s been out in room temperatures over 90°F (32°C) then it is best to consume within a day or two. Any longer than that and it’s best to discard. 

If you have any questions we’d love to hear from you. Just leave a comment below and we’ll get back to you as soon as we’ve finished cooking!