Some years ago, while rummaging through my uncles garage, I came across an old stock pile of items issued to him during the Vietnam War. Among those items, were several cans of C-Rations. At the time, I was fascinated to find these cans painted in OD Green. I felt like I had hit a gold mine. While they had been given to him during his time in service, who knows how long they had been sitting around before then–Perhaps since around WW2. It didn’t matter, because I was determined to taste this Army staple of yesteryear’s past.
What presumably was some sort of spam tasted, well, lets just say, I have no idea how they ate that. The crackers had no flavor, but were also not stale. There were other things I ate that I can’t remember. But, what I do remember is I never got sick. Not that it had ever crossed my mind that I would have.
So, why all the hype with rotating your food stores. I mean people are fanatical with rotating food almost to the point of absurdity; moreover, many people feel they need to open cans and consume the contents by the date stamped on the can. I have cans that I have stored for years and would not hesitate opening and eating from, And, quite frankly, done so.
Just how long does can food last then without going bad, then?
Dale Blumenthal, a staff writer for the FDA, wrote the following
The steamboat Bertrand was heavily laden with provisions when it set out on The Missouri River in 1865, destined for the gold mining camps in Fort Benton, Mont. The boat snagged and swamped under the weight, sinking to the bottom of the river. It was found a century later, under 30 feet of silt a little north of Omaha, Neb.
Among the canned food items retrieved from the Bertrand in 1968 were brandied peaches, oysters, plum tomatoes, honey, and mixed vegetables. In 1974, chemists at the National Food Processors Association (NFPA) analyzed the products for bacterial contamination and nutrient value. Although the food had lost its fresh smell and appearance, the NFPA chemists detected no microbial growth and determined that the foods were as safe to eat as they had been when canned more than 100 years earlier.
The nutrient values varied depending upon the product and nutrient. NFPA chemists Janet Dudek and Edgar Elkins report that significant amounts of vitamins C and A were lost. But protein levels remained high, and all calcium values “were comparable to today’s products.”
NFPA chemists also analyzed a 40-year-old can of corn found in the basement of a home in California. Again, the canning process had kept the corn safe from contaminants and from much nutrient loss. In addition, Dudek says, the kernels looked and smelled like recently canned corn.
The Canning Process
Food-spoiling bacteria, yeasts and molds are naturally present in foods. To grow, these microorganisms need moisture, a low-acid environment (acid prevents bacterial growth), nutrients, and an appropriate (usually room) temperature.
Dennis Dignan, Ph.D., chief of FDA’s food processing section, explains that foods are preserved from food spoilage by controlling one or more of the above factors. For instance, frozen foods are stored at temperatures too low for microorganisms (bacteria, yeasts and molds) to grow. When foods are dried, sufficient moisture is not available to promote growth.
It is the preservation process that distinguishes canned from other packaged foods. During canning, the food is placed in an airtight (hermetically sealed) container and heated to destroy microorganisms. The hermetic seal is essential to ensure that microorganisms do not contaminate the product after it is sterilized through heating, says Dignan. Properly canned foods can be stored unrefrigerated indefinitely without fear of their spoiling or becoming toxic.
Foods with a naturally high acid content–such as tomatoes, citrus juices, pears, and other fruits–will not support the growth of food poisoning bacteria. In tests, when large numbers of food poisoning bacteria are added to these foods, the bacteria die within a day. (The exact amount of time depends upon the bacteria and amount of acidity.) Foods that have a high acid content, therefore, do not receive as extreme a heat treatment as low-acid goods. They are heated sufficiently to destroy bacteria, yeasts and molds that could cause food to spoil.
Canners and food safety regulators are most concerned about foods with low acid content, such as mushrooms, green beans, corn, and meats. The deadly Clostridium botulinum bacterium, which causes botulism poisoning, produces a toxin in these foods that is highly heat-resistant. The sterilization process that destroys this bacteria also kills other bacteria that may poison or spoil food.
Low-acid canned foods receive a high dose of heat–usually 107 degrees Celsius (250 degrees Farenheit) for at least three minutes. (The amount of time the food is heated, though, depends upon the size of the container and the product.) The canned food is heated in a retort, a kind of pressure cooker.
Another critical element in the canned food process is sealing products in air-tight containers. It is essential that air be removed from the container before sealing. Air could cause the can to expand during heating, perhaps damaging the seals or seams of the container.
A telltale sign of loss of this vacuum–and a possibly contaminated product–is a can with bulging ends. If a seal is not airtight, bacteria may enter the can, multiply, and contaminate the product.
The hermetic seal finesses the canning process. The bacteria in a food and container are killed through heating, and at the same time new bacteria are kept from contaminating the food.
(Taken from a chart for retailers developed by FDA and NFPA and published bythe Association of Official Analytical Chemists.)