Why Does Canned Food Last Long?

Canned Food Expiration

Nicolas Appert discovered the process of canning in 1809. In the early 19th century, Napoleon offered 12,000 francs to any inventor who could devise a cheap and effective method of preserving large amounts of food. As a result, he successfully preserved the army supplies and a new food life enhancement technique called canning.

Canning has revolutionized the preservation of food. It is one of the most popular techniques for extending the shelf life of edibles. From baked beans to pineapple slices, a wide variety of food can be preserved by canning. Moreover, they’re affordable, convenient, and easily accessible.

Why does canned food last long?

Canned food has an extended shelf life due to factors that help preserve its quality and prevent spoilage. Here are some reasons why canned food can last for a long time:

Thermal Processing: Canned food undergoes a thermal processing method called commercial sterilization. The food is sealed in airtight containers, typically cans, and heated to high temperatures to destroy bacteria, yeasts, and molds that can cause spoilage. This process kills most microorganisms, including those that cause foodborne illnesses, helping to prevent the growth of spoilage-causing bacteria.

Airtight Sealing: Canned food is tightly sealed in metal cans or jars, creating a barrier that prevents the entry of oxygen and microorganisms. This airtight sealing prevents the food from being exposed to air, which helps to preserve its freshness and to avoid spoilage. It also protects the food from contamination during storage.

Lack of Moisture: Canned food is processed with heat and sealed in airtight containers, reducing the cans’ moisture content. Microorganisms require moisture to grow and multiply, and by minimizing the moisture available in canned food, the growth of spoilage-causing bacteria, yeasts, and molds is inhibited.

Acid or pH Levels: Some canned foods have a naturally low pH or are acidified during processing. The acidic environment inhibits the growth of many microorganisms, including bacteria that can cause spoilage or foodborne illnesses. Examples of acidic canned foods include fruits, tomatoes, and pickled vegetables.

Packaging Materials: Canned food is typically packaged in metal cans or glass jars that provide a protective barrier against light, oxygen, and moisture. These packaging materials help maintain the quality and integrity of the food inside, reducing the risk of spoilage.

Louis Pasteur demonstrated the role of microbes in food spoilage. Canning works on a principle known as Heat sterilization.

  • Heat Sterilization is the application of high heat to kill any microorganism present in the food or the can.

The first step in canning is filling the food in the cans. The most common material for making cans is tinplate, owing to its resistance to corrosion. However, steel cans and aluminum cans with an inner layer of tin are used on a wide scale. In the next step, sugar syrup or brine is added to the food in cans. This enhances the taste and ensures food is not burned during high heat. Air is then removed from the cans, and the cans are sealed.

  • Removal of air helps eliminate the risk of oxidation during storage.

While sealing makes sure no external microorganism, foreign material, moisture, or light can enter the can. The cans are subjected to a high temperature, generally above 100 degrees Celcius or 212 degrees Fahrenheit at high pressure. The primary causes of food spoilage are bacteria, mold, and fungi.

  • The application of such a high amount of heat kills all the spoilage-causing micro-organisms in the can, and since the can is sealed, there is no way for them to enter inside it.

Therefore food remains microbe-free and hence is not spoiled for a long time. The cans are then cooled and labeled. Canned foods require no preservatives and can be kept at room temperature.

Preserving food for over a day is impossible, but canning food can be kept safe for 1 to 5 years. In 1974, samples of canned food from the steamboat wreck that sank in 1865 were tested. There was no trace of microbial growth, and the 109-year-old food was still considered safe to eat.

These days, many new techniques like freeze-drying and aseptic packaging are used to prolong the shelf life of foods. But canning remains the most popular choice owing to its low cost and high reliability.

Frequently asked questions

How long does canned food last?

Canned foods don’t have an expiration date. Instead, the two leading labels can include the “Best Buy” or “Used by” date.

The best-by date is optimal freshness. Something is gone beyond the best by the date. It typically can lose color, texture, flavor, and nutritional value. Best Buy recommends using the product for the best physical and sensory quality. The food manufacturer recommends the date.

So there are a few downsides to keeping this for an extended period. According to the USDA, it does not change the safety factor. Typically they’ll say up to 6 years or so and sometimes between that. One of the things that’s a little different is that acidic-type foods like tomatoes go bad quicker than pH-balanced foods like lima beans.

The “use by” date refers to the product’s final days to peak freshness, flavor, and texture. After this date, the quality of the food deteriorates, but it’s still edible. Therefore, the food manufacturer recommends this data.

When you have a Best Buy or used by, you should use the canned foods within a couple of years for the best product quality.

What are the disadvantages of canned food?

Canning helps preserve food for longer periods. However, there are some disadvantages of canned foods.

Firstly, canned foods can be high in sugar and salt. So, they can pose a risk for people with high blood pressure, diabetes, obesity, etc.

Secondly, most cans have a coating of Bisphenol A to prevent corrosion. However, studies suggest that Bisphenol A can leak into food and negatively affect hormones.

Thirdly, the acids present in food can react with the metal can. Acids produce hydrogen gas, creating bulges, thus making food unsafe to eat.

Lastly, an improper canning process can lead to the growth of dangerous Clostridium botulinum. It produces a lethal toxin that, if consumed.

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“Arctic Explorers Uncover (and Eat) 60-Year-Old Food Stash”. Smithsonian.
Blumenthal, Dale. “The Canning Process; Old Preservation Technique Goes Modern.” FDA Consumer.
Applied Nutrition and Food Technology, Jesse D. Dagoon.
Geoghegan, Tom. “The story of how the tin can nearly wasn’t.” BBC News.

Julia Rose

My name is Julia Rose. I'm a registered clinical therapist, researcher, and coach. I'm the author of this blog. There are also two authors: Dr. Monica Ciagne, a registered psychologist and motivational coach, and Douglas Jones, a university lecturer & science researcher.I would love to hear your opinion, question, suggestions, please let me know. We will try to help you.

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