How long can milk stay out of the fridge before spoiling?

In this brief guide, we will answer the question, ‘how long can milk stay out of the fridge before spoiling?’. We will discuss the milk variants available in the market and how quickly each spoils. We will discuss the factors which contribute to the spoilage of milk. 

How long can milk stay out of the fridge before spoiling?

Milk can stay 2 hours out of the fridge at a temperature greater than 41 Fahrenheit, or for an hour if the temperature exceeds 90 Fahrenheits. Pasteurized milk will spoil sooner than UHT Milk.

How does milk spoil?

Milk is home to bacteria such as lactococci and lactobacilli. At temperatures above room temperature, they breed and reproduce. The probiotic bacteria change the lactose milk sugar into its compositional units; glucose and galactose.

The formation of lactic acid starts, as proved by the familiar tangy smell and taste. As the casein develops, the curdling process starts. 

As milk deteriorates further, the bacteria take over the fats, which causes the occurrence of molds.

Spoilt raw milk may become inedible as it curdles and gains its distinct sour taste and odor.  However, it does not need to be discarded, as curdled milk is used to make cheese, cream, and kefir.

On the other hand, pasteurized milk does not become sour due to the absence of bacteria that cause the milk to curdle. Instead, it rots and becomes unfit for consumption.

As milk spoils, it develops undesirable characteristics. Even if milk seems safe, you can expect bacterial growth to start at a temperature greater than 40 Fahrenheits. 

The US Food and Drug Administration advises against leaving your milk out of the fridge for more than 2 hours. The 2-hour benchmark becomes 1 instead, in case the temperature exceeded 90 F.

As milk spoils, you can detect a rancid and sour smell. 

The texture and consistency change too and, the color becomes pale with a yellowish tinge. 

How to store milk?

Milk must be stored in the fridge, in its original packaging. 

Aseptic Milk, packaged after processing at an Ultra High Temperature, will last for six months if the seal was left intact.

However, an opened tetra pack will spoil if left out of the fridge for a few hours. Pasteurized milk cannot be left at room temperature for more than 2 hours.

The pasteurization process kills bacteria by heating the milk at high temperatures. After potentially harmful microorganisms destroy, then it is aseptically sealed to ensure its longevity.  Once the seal has broken, pathogenic microorganisms cause the milk to spoil.

Other FAQs about Milk which you may be interested in.

How long is formula good for in the fridge?

Why can’t you drink a gallon of milk?

How to make milk curdle?

Pasteurization versus UHT Treatment 

Milk bought from a store is in either of the three forms. It could be either raw, pasteurized or UHT treated.

What is the Pasteurization process?

 Milk is sometimes, however, only pasteurized and not subjected to ultra-high Treatment. Pasteurized milk is not shelf-stable and needs to be refrigerated at all times. 

Pasteurized Milk lasts only four hours at room temperature. When other factors come into play, your pasteurized milk will last anywhere from three to six hours.

In pasteurization, the milk is first chilled and then heated. Milk is allowed to move between heated stainless steel plates at a temperature of 161 F. The heating occurs for 15 seconds only. Then the temperature is brought down again from 161 F to 39 F before it is packaged and distributed.

What is UHT treated milk?

Ultra-High Treatment differs slightly, as milk, is heated at 136 to 145 Fahrenheits for only 2-4 seconds. 

As pasteurized milk is heated to a cooler temperature, it is more prone to spoilage. Some bacteria tend to survive during the process, thus require constant refrigeration. 

 It has to be refrigerated at 2-6 C and, the shelf-life lasts for 2-5 days.

Milk treated to UHT lasts much longer than pasteurized milk and hence, is processed and sold at room temperature. 

What affects the shelf-life of milk?

If milk was not handled, processed, or shelved properly; the milk will have a shorter shelf-life. Even if it is unopened proper handling is important before and after packaging. 

Unopened milk can sit out for anywhere from a couple of hours to months, while opened will spoil quicker than packaged milk.

If your raw, unpasteurized milk handling were not in alignment with the standard operating procedures, at the farm and after, its standard shelf-life would be shorter. 

It is best to throw out milk that was left at room temperature or above. Milk can potentially make a person sick if it was not promptly refrigerated. Spoilage signs could be visible as the smell and texture change. According to the FDA, milk can still be unsafe for consumption if left out of the fridge.

In this brief guide, we answered the question, ‘how long can milk stay out of the fridge before spoiling?’. We discussed the milk variants available in the market and how quickly each spoils. We also discussed the factors which contribute to the spoilage of milk. 

Citations

https://www.usdairy.com/news-articles/why-is-milk-pasteurized-4-questions-answered

https://www.myrecipes.com/extracrispy/how-long-can-milk-be-out-of-the-fridge

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Hi, I am Charlotte, I love cooking and in my previous life, I was a chef. I bring some of my experience to the recipes on this hub and answer your food questions.