How to store canned food after opening

In this brief guide we will answer the question, “how to store canned food after opening?” as well as other questions pertaining to the subject at hand like how long does canned food take to go bad. Moreover, we will also discuss how to tell if canned food is bad and what happens if you eat spoiled canned food. 

How to store canned food after opening?

Storing canned food after opening it is the most critical step. The best way to store canned food after opening is to put it in an airtight container, seal it properly and put it in the refrigerator at 40 °F or below. Note that the brine solution (the watery mixture in the can) should not be discarded, rather poured into the container along with the contents of the can (1,2). 

You should never use the same can for storing canned food because it will not be airtight. Moreover, the moisture will make the can rust and it will create an off odor in your food (1). Airtight containers made of glass are ideal, but you can also use plastic containers for this purpose. When canned food has been successfully transferred into such a container, it is best to now put it in the refrigerator (2). 

Why should you not store canned food in the can?

You should not store canned food in the can because of metal corrosion in cans. Metal corrosion in food cans occurs when moisture interacts with specific metals like tin, iron, and lead. This leads to galvanic cells forming, where different metals with varying dissolution potentials are coupled (3). 

The active metal dissolves, producing ions that form insoluble salts on the surface. Spontaneous corrosion occurs at the cathode, causing hydrogen release, oxygen reduction, or electron consumption. Examples of localized corrosion in cans include stress corrosion, sulfide black corrosion, sulphur staining, pitting corrosion, and filiform corrosion (3,4).

These food–metal interactions not only affect the shelf-life of food products but can also affect human health in case of food consumption from corroded containers (4).

How long does canned food take to go bad?

If unopened, canned food is usually best for at least 6 months before it goes bad. The best way to find out is to read the “best by” date mentioned on the container. Depending on the concentration of brine and the processing, canned fruit can also last up to 18 months (5). 

High acid foods such as tomatoes and other fruit will keep their best quality for up to 18 months before going bad; low acid foods such as meat and vegetables, 2 to 5 years (5).

Open canned food usually takes 5-7 days before it goes bad. Acidic foods usually last longer than other food items like meat and poultry that last for 3-5 days (6). 

In case of fruits, you can store them for up to 6 months if sealed properly in airtight containers. Freezing does wonders for canned fruits! (1)

Can you freeze opened canned food?

Freezing opened canned food is not recommended. Canned foods are typically not formulated for freezing, as the texture and quality may deteriorate. It is best to consume the opened canned food or refrigerate it for short-term storage instead (1).

However, if cans are accidentally frozen, its structural integrity may be compromised, leading to potential bacterial contamination. If a can has frozen but remains intact and shows no signs of swelling or damage, it can be safely defrosted in the refrigerator and consumed. However, if the can has thawed at temperatures above 40 °F (4 °C), it is advisable to discard the contents as they may have been exposed to harmful bacteria (1,7). 

Cans that have thawed and refrozen are also considered unsafe and should be discarded. It’s important to prioritize food safety and use caution when dealing with accidentally frozen canned food (7). 

How to tell if canned food is bad or spoiled?

To tell if canned food is bad you should be able to identify the signs of spoilage such as unpleasant odors, tastes, and textures. You can also check the can condition before buying or eating it to avoid contamination.

Look for holes/rust. 

If your canned food has some holes or rust on the inner side when you open the lid, it means that the quality of the food product has been compromised. Consuming such a food may negatively affect your health and you should toss it in the bin or return it to the shop owner if freshly bought (1). 

Mould and bacteria growth

Because of the high moisture content inside the can, there are greater chances of mould and bacteria to grow. If you see any visible growth besides the food product, you should immediately discard the can. Visible growth means either the can was punctured or that you let it out in the open for too long after opening (8). 

Shrunken or inflated can

If the can is inflated or shrunken, it means that the integrity of the can was damaged during the handling or the distribution process. This affects the shelf life of the food product inside the can, and your product may expire even before the said “best by” date. You should not purchase a can that looks overly bloated or shrunken (1).

Improper sealing

Another common mistake is improper sealing. Note that the seal is where the lid of the can is present. An improper seal could be due to a malfunction in the machine that sealed it or due to poor handling practices during distribution. Remember that the seal is the weakest point of the can because it is supposed to be opened. If you notice the integrity of the seal compromised in any way, chances are that your food product is already spoiled, or will spoil before its “best by” date (1).

Swollen cans

Swollen cans most times do occur and usually contain gas produced by members of the genus Clostridium or spoilage-causing organisms.  Do not use any swollen cans; discard them (1).

What happens if you eat spoiled canned food?

If you consume spoiled food you are prone to foodborne disease like botulism caused by the bacteria Clostridium botulinum, Listeria, Salmonella and E. coli infection (9).

Symptoms of foodborne illness include (10):

• Nausea
• Vomiting
• Diarrhea 
• Stomach pain
• Fever

Botulism is a lethal food illness caused by C. botulinum bacteria that flourish in oxygen-free environments, such as inadequately processed canned goods. The absence of air in cans allows these bacteria to multiply, producing toxins. Low-acid foods like green beans, maize, beets, and peas pose a higher risk as they may contain C. botulinum spores from the soil (1).

To avoid botulism, thoroughly inspect any canned food that appears suspect and discard any cans with signs of spoilage.

If you’ve consumed spoiled canned food and suspect food poisoning, monitor symptoms, stay hydrated, seek medical help for severe symptoms, keep the can as evidence, and report the incident to food safety authorities. Prevent future risks by checking canned food for spoilage and discarding any compromised cans.

Conclusion

In this brief guide we have addressed the question, “How to store canned food after opening?” as well as other questions pertaining to the subject at hand like how long does canned food take to go bad. Moreover, we also discussed  how to tell if canned food is bad and what happens if you eat spoiled canned food.

References

1. Shelf-Stable Food Safety. USDA, 2013.

2. After you open a can, how long can you keep the food in the refrigerator? USDA, 2023.

3. Montanari A, Zurlini C. Influence of side stripe on the corrosion of unlacquered tinplate cans for food preserves. Packag Technol Sci. 2018, 31(1), 15–25.

4. Deshwal GK, Panjagari NR. Review on metal packaging: materials, forms, food applications, safety and recyclability. J Food Sci Technol. 2020, 57(7), 2377-2392.

5. How long can you keep canned goods? USDA, 2023.

6. After opening canned foods, is it safe to refrigerate the unused food in the can?. USDA, 2023.

7. Is it safe to use cans that freeze accidentally?. USDA, 2023.

8. Ogbulie, T.E. Assessment of the Safety of Some On-The-Shelf Canned Food Products Using PCR-Based Molecular Technique. Nigerian Food Journal, 2014, 32, 2, 81-91.

9. Bintsis T. Foodborne pathogens. AIMS Microbiol. 2017, 3(3),529-563.

10. What You Need to Know about Foodborne Illnesses. FDA, 2022.