Can canned tuna go bad?

In this brief study, we will answer the question, “Can canned tuna go bad?” Additionally, we will discuss the shelf life and the storage of canned tuna. 

Can canned tuna go bad?

Canned tuna can go bad after its best-before date, or if improperly stored or handled during its shelf life. After opening the can, tuna goes bad within a few days in the refrigerator.

What is the shelf life of canned tuna?

The shelf life of canned tuna is about 4 to 5 years. Did you find this shelf life too long for a food product stored at room temperature? Don´t worry, let´s understand why! 

Canned goods undergo sterilization, a preservation technique in which food is placed in airtight, vacuum-sealed containers and heat processed at 121 °C for a few minutes. As a result, the food becomes commercially sterile [1].

As the food cools, a vacuum seal is formed that prevents any new bacteria from getting in. Thus, as long as the canned good stays sealed in the package and is properly handled, sterility is maintained, and no microorganisms develop [1].

 Here is why canned tuna lasts for so long!

What factors can limit the shelf life of canned tuna?

According to the United States Department of Agriculture (USDA) [1], there are several factors that limit the shelf life of canned foods, including canned tuna:

  • Rust and deformations: cans can rust over time. Shipping accidents, where cans fall and dent or are crushed, also cause container problems [1]. Don’t purchase bulging, rusted, leaking, or deeply dented cans.
  • Corrosion: naturally present chemicals in food continually react with the container. Over several years, this can cause taste and texture changes. The nutritional value can also be affected [1].
  • Storage conditions: high temperatures (over 37 °C) are harmful to canned goods such as canned tuna.

Sterilization gets rid of microorganisms growing at room temperature, but the risk of spoilage due to thermophilic bacteria jumps sharply as storage temperatures increase [1].

Thus, keep your canned tuna away from the stove or hot places, like under the sink, damp garage or basement, or in any place exposed to high or low-temperature extremes. 

Is canned tuna safe to eat after the expiration date has passed?

It is safe to eat expired canned tuna as long as the product has been well stored, and the can does not present crushing, rust, dents, or swelling [1].

If all these criteria are met, the canned tuna is supposed to be still sterile, and the product to be safe [1].

Indeed, canned tuna has a best-by date rather than an expiration date, which indicates that the tuna is at its finest if consumed before that date.

In other words that means that passed the best-by date, the product is still safe, but it is possible that chemical reactions have taken place during the storage time, so upon opening, the tuna may not taste good.  

After opening the can, how long does the tuna last?

After opening the can, tuna should be consumed immediately. If you do not consume the whole portion on the same day, transfer the can content to an airtight container and keep it in the refrigerator for no longer than two days.

Unopened, tuna is maintained in a sterile environment, but as soon as tuna enters into contact with ambient conditions, microorganisms will find a very favorable situation to develop: nutrients, water, and adequate pH (5-6).

If you want to prolong the shelf life of canned tuna leftover, then you should freeze it. Frozen, tuna lasts about three months [2].

 What is the best way to store canned tuna?

  • Unopened: the best way to store canned tuna when unopened is in a dry and cool place, avoiding proximity to a stove or any hot places. Temperatures below 30 °C are best [1]. 

Heat can promote the oxidation of tuna fat and the oil covering it, reducing the product quality. 

Moreover, according to the USDA [1], unusually high-temperature storage (above 50 °C) may result in harmless thermophilic bacteria multiplying and swelling or souring the product. If this happens, the tuna should not be eaten.

  • After opening:  Leftover tuna should be moved from the can into a hermetically sealed container and refrigerated promptly if it is going to be used within 2 days after being opened. 

To prolong the shelf life of the tuna it is recommended to freeze it. Frozen, tuna lasts for about three months [2].

For this, transfer any remaining tuna to a separate airtight container or appropriate bag [1]. 

Tuna should be flattened from the bottom of a freezer-safe bag to achieve consistent freezing. Additionally, remove as much air as possible before freezing.

Freezing drastically reduces the velocity of biochemical reactions and microbial development, that´s why when you freeze food, it lasts longer than in the refrigerator [2]. 

To thaw frozen tuna, move it from the freezer to the refrigerator and leave it overnight or until completely thawed [2].

Is it possible to freeze or refrigerate tuna in the can?

It is possible to freeze or refrigerate tuna in the can, but it is not recommended, especially after opening it. 

If unopened, it does not make much sense to cool or freeze canned tuna. The main goal of refrigerating or freezing foods is to delay chemical reactions and microbial growth to prolong the shelf life. 

As canned tuna is commercially sterile, chilling will not add any days to your product or contribute to extending the shelf life.

After opening, the tuna should be moved to a hermetical container or bag. Storing the tuna in the cans favors exposure to air, which can bring contamination, promote oxidation reactions, and loss of flavor, and aroma [2].

Besides, the tuna smell can be transferred to other foods in your refrigerator or freezer. 

How to tell that canned tuna has gone bad? 

You can tell that canned tuna has gone bad by following these tips:

  • Carefully examine the can and make sure that it is completely intact. At any sign of rust, dents, or swelling do not consume it.

Holes in cans, even micro holes or fissures, can be a window to microbe contamination. Discard the can [1].

Swelling is critical to canned goods because may indicate that commercial sterilization has not been achieved properly due to processing faults. 

Unless you are sure of the cause of the swelling, the can must be discarded.

  • If everything looks fine with the can, open it, and taste it to check the sensory quality. 

Sensory changes are the main alterations taking place over time in canned tuna. For example, taste changes can be produced mainly by fat oxidation.

If when tasting canned tuna you feel it rancid, it means that the fat has been oxidized. 

It will not make you sick immediately, but I do not recommend you eat oxidized foods because depending on the oxidation extent, toxic compounds may have been produced [3]. 

  • After opening and during storage, any change in color, texture, or smell may indicate that the tuna is rotten and should be thrown away. 

Conclusion

In this brief study, we answered the question, “Can canned tuna go bad?” Additionally, we discussed the shelf life as well as the storage of canned tuna. 

Citations

  1. http://bromatopesquisas-ufrj.blogspot.com/2011/12/avaliacao-do-prazo-de-validade-em.html
  1. https://www.fsis.usda.gov/food-safety/safe-food-handling-and-preparation/food-safety-basics/shelf-stable-food
  1. https://www.fsis.usda.gov/food-safety/safe-food-handling-and-preparation/food-safety-basics/freezing-and-food-safety

4. Vieira SA, Zhang G, Decker EA. Biological Implications of Lipid Oxidation Products. Journal of the American Oil Chemists’ Society. 2017;94(3):339-51.