Food preservation

How to Know if Soup is Spoiled

Nidhi Nangia
By Nidhi Nangia. Updated: August 20, 2018
How to Know if Soup is Spoiled

Have you ever accidentally or intentionally left your soup in the pot overnight? When you wake up in the morning and see that you left your soup on the counter without refrigerating it, then naturally you might wonder whether your soup is still safe for consumption or has been spoiled. Most foods have a best-before date informing you about when your food goes off. When it comes to soup, it is generally safe to be consumed for 3-4 days after preparation, and you can freeze it for as long as 2-3 months. Making soup requires time and effort therefore tossing it in the bin without thinking twice is a rare possibility.

But don't worry, here at OneHOWTO we will tell you how to know if soup is spoiled.

You may also be interested in: How to Tell if Beef Is Spoiled


  1. How to know if my soup is spoiled
  2. Re-Boiling Soup to Kill Bacteria and Prevent Spoilage
  3. Keeping Soup at Right Temperature

How to know if my soup is spoiled

If your soup is spoiled, you will notice a number of unpleasant changes regarding its: taste, texture, smell and appearance. Here are a few ways to know if your soup is still safe to consume:

  • Visually inspect the soup: Look at your soup to visually inspect it. It should appear in its original color without any signs of mold. Even if you notice some coagulated fat in the soup before you heat it, it should not appear cloudy. In addition, there should be no sediment in it.
  • Smell the soup: When you smell your soup, it should give off a pleasant aroma. If your soup smells sour or unpleasant, then it is likely spoiled and should be discarded. If your soup smells rancid or sour, then you should never taste it to check further. Tasting food that is spoiled may make you sick.
  • Look at the container: If you have stored your soup in a container or if it is a ready-made soup that came in a container, then looking at the container can give you an idea of whether it is spoiled or not. If the container seems to appear swollen or bulging, then the content inside it is probably spoiled. Yeast and bacteria that spoils food release gases which fill the soup container, causing it to break open or expand. Sharp or large dents on the can may also allow bacteria to enter inside the soup, causing spoilage. If the soup’s can has been opened and appears rusted or swollen, then it may have gathered botulinum toxin which is extremely harmful for the environment. You should boil the can in water for 30 minutes before discarding it to detoxify it.
  • Was the soup stored correctly?: The way you store your soup largely affects its life-span. Once made or opened, you need to refrigerate it below 40°F within a couple of hours. If you leave your soup out of a fridge without refrigeration for more than 2 hours, it may become spoiled and you should discard it. If you have recently made a big pot of soup, pour it into several small containers and keep them in the refrigerator. Small containers cool down more rapidly, thus preventing growth of bacteria in the soup.
  • Check the expiry dates: Once you open a can of soup, it has a shelf life of 4-5 days if kept in the refrigerator. Freshly made soup also lasts for around 6 days, provided that they are kept in a refrigerator. Home canned soup can last up to a year if kept in the pantry. Commercially canned soup can last 2-5 years if stored in a dry, cool pantry. Frozen soup can stay at 0°F for an indefinite period of time. The ‘use by’ or ‘best by’ date on the soup indicates the time when the soup will be at its peak quality. If the soup has passed its expiry date, it does not necessarily mean that it has been spoiled. In this case, use the other mentioned methods to check whether or not the soup is spoiled.
  • Taste the soup: If your soup was properly stored, looks and smells good and if there are no signs of dent or swelling on the container, then you can check the soup by taste. If it does not taste sour or spoiled and if you don’t feel like puking it instantly, then it’s fine to be consumed. If it tastes rancid, foul or unpleasant, then it is spoiled and you should not think twice before discarding it.

Re-Boiling Soup to Kill Bacteria and Prevent Spoilage

Some people think that re-boiling soup makes it safe for consumption. While re-boiling can kill some of the bacteria like salmonella and E. coli, other harmful species of bacteria, such as the bacteria that causes botulism, form inactive spores that can survive the process of re-boiling. Once soup cools down after re-boiling, these spores may start germinating and can multiplying quickly.

Re-boiling soup can kill active bacteria, but keeping it on boil for 10 minutes may inactivate some botulism toxin as well. If you left your soup out of the refrigeration overnight, you can reboil it in the morning and refrigerate. This step generally makes soup fit for consumption, because it was not cool enough to allow germination and reproduction of bacteria.

But, if your soup was left out without refrigeration for 3 days, then it is likely to have developed infectious: Bacillus cereus cells, Clostridium botulinum, Clostridium perfringens cells with high level toxins. Re-boiling this type of soup may make the soup safe to consume by killing the bacteria, but it may also compromise taste, flavor and smell.

Soup left out for more than 3 days may become safe after re-boiling, but it has likely accumulated millions of dead bacteria and inactivated toxins. Therefore, your soup will most likely taste different, as the bacteria would have feasted on the soup’s amino acids and sugars.

How to Know if Soup is Spoiled - Re-Boiling Soup to Kill Bacteria and Prevent Spoilage

Keeping Soup at Right Temperature

Most people know that soup and other food items can be kept safe by refrigerating them, but have you ever wondered what’s the right temperature to store your foods? Refrigerators have a large temperature range and you need a refrigerator thermometer to know at what temperature your refrigerator is generating. Ideally, you can keep your food at 4°C or 40°F, but for no more than 4 days.

People use their refrigerator as an ideal food safety device, but they don’t have any idea what its temperature should be. Keeping food at right temperature stops bacteria growth that cause spoilage or pathogens. While a healthy person can consume soup left outside overnight without refrigeration, a person who is already sick with a weak immune system may have higher risk of getting ill after consuming day old soup. The best thing you can do is to re-boil the soup for 10 minutes to kill off any present bacteria. It’s best to discard any soup that was left non-refrigerated for more than 4 days.

If you want to read similar articles to How to Know if Soup is Spoiled, we recommend you visit our Food & drink category.

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What did you think of this article?
martin harris
Question: when a number of some very small flies have died in my honey, does heating my coffee for 3 minutes in the micro-wave kill the pathogens?
Martin Harris
OneHowTo Editor
Hi Martin,

A microwave will likely kill most bacteria and many microorganisms, but it depends on what they are. We would say the risk is small, but there may still be one.
When I used my soup maker my soup was all frothy when ready.what would have caused this to happen.would the vegetables been off.i haven't had this problem before and would be grateful for you're comment.soup got binned.
OneHowTo Editor
Hi Margaret,

If there was any milk, cream or other similar products in the soup, it is possible it will froth with the blender. Actually, even soup with just stock can become a little frothy. Usually it will just settle on its own. The soup should still be edible, but if you are making a creamy soup, we advise adding the creaming agent after you blend the other ingredients. Hope this helps!
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How to Know if Soup is Spoiled