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Meta Description: Canning represents a food preservation technology that extends the shelf life of food packaged in a hermetically sealed container. Developed some two hundred years ago, the canning process aims to prevent food spoilage and preserve the quality of the foods, so that food can be kept for an extended period of time without refrigeration and without the loss of nutrition values.

Keywords: Canned Food، Botulism، Shelf-Life، bisphenol A، canning

o ensure adequate intakes of the essential nutrients contained in such energy sources.

Introduction:

 

Napoleon is considered “the father” of canning. He offered 12,000 French francs to anyone who could find a way to prevent military food supplies from spoiling. Napoleon himself presented the prize in 1795 to chef Nicholas Appert, who invented the process of packing meat and poultry in glass bottles, corking them, and submerging them in boiling water. Without realizing it, he sterilized them, stopping bacterial spoilage and growth.

This military secret soon reached England where, in 1810, Peter Durance patented the use of metal containers for canning. Englishman William Underwood migrated to Boston and established a canning plant in 1821. This was the beginning of canning in the United States. Underwood (even today, a brand of “deviled ham”) is America’s oldest canning company.

Canning represents a food preservation technology that extends the shelf life of food packaged in a hermetically sealed container. Developed some two hundred years ago, the canning process aims to prevent food spoilage and preserve the quality of the foods, so that food can be kept for an extended period of time without refrigeration and without the loss of nutrition values.

How does canning make food shelf stable?

Canning is a way to store food for long periods of time. It is a method of preserving where food is placed in airtight, vacuum-sealed containers and heat processed at 250 °F (121 °C). This destroys microorganisms and inactivates enzymes. As the food cools, a vacuum seal is formed that prevents any new bacteria from getting in. Since the food in the container is commercially sterile, it does not spoil. Once the container is opened, however, bacteria can enter and begin growing in the food. Any unused portions must then be refrigerated in clean containers.

What Are the Advantages of Canning Food?

Foods Out of Season:

Home canning foods, particularly fruits and vegetables, has the advantage of making seasonal produce available year-round. Before the advent of refrigeration, home canning meant you could have fruits and vegetables in winter when nothing is growing. While modern imports make most fruits and vegetables available all year, out-of-season fruits are invariably expensive. Canning your own fruits and vegetables as jam, whole fruits or pickles at the height of their seasons ensures the availability of summer fruit flavors during the winter.

Convenience:

Fresh vegetables and fruits have a hard time beating the convenience canned foods can offer for those with busy lifestyles. Whether you’re a busy parent or just an active person, keeping canned beans and vegetables on hand can let you quickly and spontaneously prepare soups, stews, and even salads

Long Shelf-Life:

The advantages of canned food over fresh produce also include a longer shelf life for unopened cans. As a general rule, unopened home-canned foods have a shelf life of 1 to 1.5 years. Commercially canned foods should retain their quality until the expiration date printed on the can. For most canned goods, this date is 2-5 years from the manufacture date.

The canning of foods has resulted in a wider choice of nutritious, good-quality foods being available all year round in a convenient form for the consumer. Although with better global links and improved agronomy, many foods are now available fresh all year round, canned foods still form an important part of the food marketplace. When considering the quality of canned foods, it is important to compare them with fresh or frozen foods at the point of consumption. Many of the changes that occur in both sensory and nutritional aspects do so during any thermal process, whether it is conventional cooking, blanching, or canning.

For most foods, the canning process replaces a conventional cooking process, and any mild reheating stage has no further significant effect on quality. Losses in heat-labile nutrients such as vitamins can be significant. However, as canned products are usually produced from materials at optimum maturity and immediately harvest, levels can often be as high as the ‘fresh’ material purchased from the greengrocers and prepared in the home.

What are the concerns about canned food?

 

Risk of Botulism:

Reported incidents of food-borne outbreaks as a result of the consumption of canned food are almost always associated with the improper application of the canning process, and improperly home-canned food is responsible for the majority of incidents. For example, more than 90% of food-borne botulism outbreaks between 1976 and 1985 in the US was due to home-canned foods that had not been properly made.

While extremely rare, a toxin or poison produced by the bacteria Clostridium botulinum ( C. botulinum) is a very serious danger in canned goods. Botulism is a deadly food poisoning. The botulism bacteria rod-shaped under the microscope grow best in anaerobic (absence of oxygen) conditions. Since the canning process forces air out of food, the C. botulinum bacteria may find incorrectly or minimally processed canned foods a good place to grow and produce the toxin. Low-acid vegetables such as green beans, corn, beets, and peas, which may have picked up C. botulinum spores from the soil, are at risk.

The botulism spores are heat-resistant, can survive in foods that are incorrectly or minimally processed, and are difficult to destroy. While high cooking temperatures will kill the normal C. botulinum organism, it takes even higher temperatures to kill the spore. That’s why the canning of low-acid foods is done with a pressure canner. If the spores are not killed in the canning process, they can become normal cells again and produce the deadly toxin.

To avoid botulism, carefully examine any canned food that looks suspicious. The risk is greater if containers have been canned at home without following safe canning procedures. Never use food from containers showing possible botulism warnings — leaking, bulging, or badly dented cans; cracked jars or jars with loose or bulging lids; canned food with a foul odor; milky liquids surrounding the vegetables that should be clear; or any container that spurts liquid when you open it. Don’t even taste the food!

Exposure to BPA:

Bisphenol A (BPA), a chemical commonly found in aluminum and tin cans, has received a lot of attention in recent years. Numerous peer-reviewed studies have shown BPA to be toxic even at low doses and have linked BPA exposure to many health problems including cardiovascular disease, obesity, diabetes, breast cancer, prostate cancer, neurological disorders, and infertility. So far, the FDA has banned the use of BPA in baby bottles and sippy cups but has refused to extend the ban to other products, saying it still needs further evidence.

Exposure to Tin and Iron

Both desirable and undesirable color effects can occur in canned goods due to reactions involving metal ions. Tin coating of the internal can surface produces a chemically reducing environment, which minimizes oxidation and helps prevent color and flavor degradation in certain products, e.g., tomato-based products and asparagus. Asparagus canned in a lacquered can may develop a dark discoloration due to the formation of a complex between rutin (a flavonol glycoside) and iron, whereas even partial exposure to tin, such as one plain can end, will retain product color.

Certain anthocyanin pigments can form metal complexes with tin and iron produced through internal

can corrosion, causing pink discoloration, especially in pears and peaches, and bluing of red fruits. Tin can cause short term gastric irritation and nausea, but it is not absorbed by the gut in significant quantities, and there is no evidence of any long-term or cumulative toxic effects.

High dietary salt and sugar content

is very harmful to the body. Salt in large amounts can cause hypertension that can severely affect the cardiovascular system. Excess sodium can affect the kidneys too and cause fluid buildup. An excess intake of sugar syrup can add extra calories to the body and may be harmful to individuals with diabetes.

Canned components may mix or chemically react with the food and be potentially toxic. The identified substances that could migrate from the can to the food include aluminum, lead (though currently it is banned from being used in making cans), and bisphenol A, also known as BPA, which is a toxic chemical that is present in can coatings). BPA protects the can from infectious agents and from corrosion. The Food and Drug Administration (FDA) informs that BPA is normally found within permissible levels in the can contents, and hence safe. However, the Mayo Clinic states that certain studies have revealed that leached BPA into canned foods may affect the brain and nervous system and prostate glands of fetuses and infants.

Do crystals in canned goods mean the food is not safe?

Canned seafood occasionally contains small fragments of a glass-like substance. According to the U.S. Food and Drug Administration (FDA), these crystals pose no danger to consumers. Known chemically as magnesium ammonium phosphate, commonly called “struvite,” the crystals can form from certain natural constituents of the fish or shellfish after they are commercially canned.

Conclusion

Should You Eat Canned Foods?

The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health (NIH), says that it is a myth that fresh foods (mainly vegetables and fruits) are always better than canned ones. It need not be the case! However, they advise checking the nutrition facts on the label (such as high fiber, vitamins, and minerals) while choosing a canned item and to pick low-salt, low-sugar, and low-sodium items or fruits soaked in water or their own juice. It is also advised to wash or rinse canned foods (as applicable) to remove any added salts and sugars before consumption.

Reference
  • http://www.mayoclinic.org/healthy-living/nutrition-and-healthy-eating/expert-answers/bpa/faq-20058331 (accessed on 08/01/2015)
  • http://www.fsis.usda.gov/wps/portal/fsis/topics/food-safety-education/get-answers/food-safety-fact-sheets/safe-food-handling (accessed on 08/01/2015)
  • http://win.niddk.nih.gov/publications/myths.htm#top (accessed on 08/01/2015)
  • Blunden, S., & Wallace, T. (2003). Tin in canned food: a review and understanding of occurrence and effect. Food and Chemical Toxicology,41(12), 1651-1662.
  • Lim, D. S., Kwack, S. J., Kim, K. B., Kim, H. S., & Lee, B. M. (2009). Risk assessment of bisphenol A migrated from canned foods in Korea. Journal of Toxicology and Environmental Health, Part A, 72(21-22), 1327-1335.
  • Cao, X. L., Corriveau, J., & Popovic, S. (2010). Bisphenol A in canned food products from Canadian markets. Journal of Food Protection®, 73(6), 1085-1089.
  • Rastkari, N., Ahmadkhaniha, R., Yunesian, M., Baleh, L. J., & Mesdaghinia, A. (2010). Sensitive determination of bisphenol A and bisphenol F in canned food using a solid-phase microextraction fiber coated with single-walled carbon nanotubes before GC/MS. Food Additives and Contaminants, 27(10), 1460-1468.

Table 2 The effect of heat processing on the major nutritional components

Table 2 The effect of heat processing on the major nutritional components

Table 2 The effect of heat processing on the major nutritional components

Nutrient Effect
Water

Loss of total solids into canning liquor

 

Dilution

Dehydration

Proteins

Enzymic inactivation

 

Loss of certain essential amino acids Loss of digestibility

Improved digestibility

Carbohydrates

Starch gelatinization and

 

increased digestibility No apparent change in the content of carbohydrate

Dietary fiber Generally no loss of physiological value
Lipids

Conversion of cis fatty acids to trans fatty acids

 

Loss of essential fatty acid activity

Water-soluble vitamins

Large losses of vitamins C and B1 due to leaching and heat degradation

 

Increased bioavailability of biotin and nicotinic acid due to enzyme inactivation

Fat-soluble vitamins

Mainly heat-stable

 

Losses due to oxidation of lipids

Minerals

Losses due to leaching

 

Possible increase in sodium and calcium levels by uptake from canning liquor