How long can soy milk sit out?

In this brief guide, we are going to answer the question “How long can soy milk sit out?” with an analysis of the shelf life of soy milk at room temperature. 

Moreover, we are going to discuss different ways to spot bad soy milk and the risks of leaving soy milk out.

How long can soy milk sit out?

Unopened shelf-stable soy milk lasts for about 6-10 months in the pantry, provided that it is clean, cool, and dry. 

This is possible because shelf-stable soy milk undergoes sterilization to make the product commercially sterile, and aseptic packaging in cartons to protect it from light, oxygen, and recontamination. 

Once you have opened the shelf-stable soy milk, it lasts for about 2 hours when left out of the fridge at room temperature [1]. If the ambient temperature hits 30°C or higher, the soy milk cannot be left out for longer than 1 hour [1]. 

Therefore, after opening it, move the carton into the refrigerator (4°C). 

The same holds true for homemade soy milk and soy milk that is sold refrigerated, it should not be left out more than 2 hours.

Chilling is necessary because bacteria grow rapidly between 4°C and 60°C, particularly at 25-30°C, and soy milk composition (mostly water, proteins, fat, carbohydrates, vitamins, and minerals) encourages microbial growth [2].

Therefore, chilling will inhibit the development of spoilage and harmful microorganisms in soy milk, extending its shelf life and ensuring safety.  

What is the optimum temperature to store soy milk?

You should always store your soy milk at 4°C or below in the fridge. Bacterial growth takes place at a faster pace between the temperature of 4 and 60°C [1].

Therefore it is always advised to store soy milk at a lower temperature to preserve its safety, freshness, and quality for a long time.

What are the risks of leaving soy milk out?

When you consume soy milk that has been left out for more than 2 hours (non-shelf-stable or after opening the milk carton), you put yourself at a high risk of poisoning. 

Soy milk is highly perishable because it has a favorable environment for microorganisms’ growth, which is boosted between 4 and  60°C [2].

Specifically, harmful bacteria, such as salmonella, prefer temperatures between 25 and 35°C.  According to studies, at such optimal temperature conditions, the bacteria population doubles every 20 min [3]. 

Common symptoms of food poisoning are diarrhea, stomach pain or cramps, nausea, vomiting, and fever.

Different ways to spot bad soy milk

To know whether your soy milk has gone bad, observe its appearance and feel its smell. 

While developing in food, fungi and bacteria release enzymes that break down soy milk components, promoting texture change, as well as metabolites that can produce color modifications, unpleasant odors, and flavors [3].

If the soy milk is curdled or has lumps present in it, it is also an indication of bad soy milk due to microbial development.

Sourness can be caused by the hydrolysis of proteins in soy milk due to the action of microbial spoilage. 

If you notice any of these signs, simply discard the soy milk.

Tips to properly store soy milk

  • Unopened shelf-stable soy milk: keep it in a clean, cool place, away from heat sources.
  • After opening shelf-stable soy milk: keep it refrigerated (4°C), and protected from light and air. You can do it by sealing the lid tightly every time you handle the pack. 
  • For homemade milk, store it refrigerated (4°C), in dark, airtight containers to make it last longer. This will reduce contamination.
  • Soy milk can pick up odors therefore it should be stored in an air-tight container or bottle in the fridge. Moreover, it should be stored away from strong-smelling food items like garlic, onion, etc. 
  • It is better to store soy milk on one of the shelves of the refrigerator rather than the door. In this area, there is significant temperature fluctuation, which may negatively impact the shelf life of the product.


In this brief guide, we answered the question “How long can soy milk sit out” with an analysis of the shelf life of soy milk at room temperature. Moreover, we discussed different ways to spot bad soy milk and the risks of leaving soy milk out.



2. Silva ARA, Silva MMN, Ribeiro BD. Health issues and technological aspects of plant-based alternative milk. Food Research International. 2020;131:108972.

 3. Jay JM. Food – Microbiology. 6th Ed, Aspen Food Science, 2000. 

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