Soy milk has become an extremely popular dairy alternative for those who are lactose intolerant, vegan, or simply want a plant-based option. But like regular dairy milk, soy milk also requires diligent food safety practices. As a perishable food product, soy milk can spoil and go bad if left out too long or stored improperly.
So how long can soy milk sit out unrefrigerated before it becomes unsafe to drink? What are the shelf life differences between shelf-stable and refrigerated varieties? How can you tell if your soy milk has gone bad? This article will cover proper soy milk handling, storage, signs of spoilage, and how long it can be left out at room temperature.
Shelf-Stable vs Refrigerated: Understanding the Difference
There are two main varieties of soy milk:
Shelf-Stable Soy Milk
Shelf-stable soy milk is processed and packaged in aseptic containers to allow for an unopened shelf life of 6-12 months. This involves high-temperature ultra-pasteurization and vacuum sealing in order to kill any bacteria and prevent contamination.
Shelf-stable soy milk can sit unopened at room temperature on pantry shelves until the printed expiration date. However, once opened it requires refrigeration and generally lasts 7-10 days before spoiling.
Refrigerated Soy Milk
Refrigerated soy milk is typically found in the dairy case alongside regular milk. It is a fresh, non-stabilized product that requires constant refrigeration, even when unopened.
Refrigerated soy milk will generally last 5-7 days after opening when stored properly in the fridge. Because it is less processed and more delicate, refrigerated soy milk spoils faster than shelf-stable.
How Long Can Soy Milk Sit Out Unrefrigerated?
So how long can an opened carton or bottle of soy milk be left out before it is considered unsafe?
The recommended maximum time soy milk can sit at room temperature is 2 hours. Similar to dairy milk, harmful bacteria can multiply quickly in soy milk when left unrefrigerated for too long.
This 2 hour window includes prep and handling time as well. For example, if you pour yourself a glass of soy milk but get distracted and leave it out for an hour before drinking it, you should discard the remainder immediately rather than putting it back in the fridge.
Warmer ambient room temperatures also shorten the safe sitting out time for soy milk even further. On a hot day, bacteria multiply faster, so soy milk should not sit out for more than an hour at temperatures above 90°F.
The bottom line is soy milk needs to go back in the fridge as soon as possible after using. Leaving it out too long creates an environment where dangerous bacteria can thrive.
Dangers of Spoiled Soy Milk
Consuming soy milk that has been left out too long and spoiled can lead to foodborne illness. Here are some of the risks:
- Harmful bacteria such as E. coli, Salmonella, and Listeria can grow rapidly in soy milk when left unrefrigerated for too long.
- Foodborne illness symptoms include nausea, vomiting, diarrhea, abdominal cramps, headache, and fever. Symptoms can appear anywhere from 30 minutes to 48 hours after ingesting contaminated soy milk.
- Vulnerable populations like children, pregnant women, elderly, and those with compromised immune systems are most susceptible to illness from spoiled dairy products. Foodborne infection can be especially dangerous for these groups.
As you can see, it’s very important to follow proper soy milk storage times and look for signs of spoilage. When in doubt, it’s best to just throw it out.
How to Tell If Soy Milk Has Gone Bad
Soy milk, like other dairy alternatives, can show distinct signs of spoilage once it has gone bad. Here are the main indications your soy milk should be discarded:
- Curdled texture – Fresh soy milk should have a smooth, creamy consistency. Curdling or clumps are a clear sign it has soured.
- Foul, sour odor – Soy milk that is still good to drink smells mildly sweet. Foul odors point to spoilage.
- Mold – Creamy white or blue-green fuzzy spots or film on the surface signals mold growth.
- Discoloration – Good soy milk is white. Yellowish or greyish discoloration indicates spoilage.
- Separation – Fresh soy milk appears homogenized. Separation of the liquids and solids points to spoilage.
- Off tastes – Rancid, bitter, or sour flavors mean soy milk should be discarded.
Trust your senses – if your soy milk smells bad, looks weird, or tastes funky, err on the side of caution and throw it away.
Proper Storage and Handling of Soy Milk
To get the most out of your soy milk and avoid foodborne illness, follow these safe storage guidelines:
- Store unopened shelf-stable soy milk in a pantry or cupboard. Avoid direct sunlight or heat sources.
- Refrigerate soy milk immediately after opening. Keep it stored in the original container or properly sealed to prevent contamination.
- Do not leave soy milk sit out at room temperature for longer than 2 hours. Only 1 hour if the room is very warm.
- Keep refrigerated soy milk stored at 40°F or below. Check that your fridge temperature is properly cold.
- When pouring soy milk, use a clean glass and utensil each time to prevent bacterial spread. Never return leftover soy milk from a glass back into the container.
- Upon each use, give soy milk a quick smell and visual inspection for signs of spoilage before consuming.
- Throw away soy milk that is past the printed expiration or use-by date, even if unopened. Use-by dates indicate peak freshness.
Following proper refrigerated storage times and avoiding temperature abuse is the best way to prevent soy milk from going bad prematurely.
What To Do With Spoiled Soy Milk
If your soy milk shows any signs of spoilage–sour smell, changed consistency, mold growth–it’s best to just discard it. Do not take chances consuming soy milk past its prime.
Here are the proper ways to get rid of spoiled soy milk:
- Discard the soy milk. Pour down the sink or place in the garbage. Never taste to confirm it’s gone bad.
- Do not attempt to salvage or recook spoiled soy milk, as harmful bacteria cannot be reversed. When in doubt, throw it out.
- Do not give spoiled soy milk to pets. It can make animals sick as well.
- Clean container thoroughly before placing in recycling bin or trash. Soy milk can leave residues that contaminate surfaces and utensils.
Being vigilant about soy milk storage, staying within safe fridge/counter time limits, and disposing spoiled product properly will help prevent the risks of foodborne illness.
The Takeaway: Enjoy Soy Milk Safely
When stored and handled properly, the average shelf life of soy milk is about 7-10 days after opening. Just like regular dairy milk it requires diligent refrigeration to prevent bacterial growth and spoilage.
Soy milk that has been sitting out for more than 2 hours (1 hour if very warm) should always be discarded. Leaving it out too long creates conditions for potentially hazardous bacteria to multiply quickly.
Look for signs of spoilage like foul smells, changed texture, mold, or separation. Never consume soy milk that is past its expiration date or shows signs it has gone bad, as this can cause foodborne illness.
The bottom line is always refrigerate soy milk immediately after use and don’t let it sit out more than 2 hours. Following proper storage methods, keeping soy milk chilled, taking care when dispensing, and staying alert to signs of spoilage will ensure you can safely enjoy all the benefits of this popular dairy alternative.
Bethany is an experienced food writer and recipe developer whose popular site Grangefarmschool.org provides home cooks with approachable recipes, cooking tips, and practical kitchen advice. Her thoroughly-tested recipes and inviting photography aim to make cooking fun and fulfilling for cooks of all levels.