Foods naturally deteriorate as they age. The science of food storage and preservation has evolved from our attempts to slow that deterioration. The prime concern with shelf life quality of foods is preventing spoilage microorganisms from growing. This is done through food preservation methods (drying, canning, etc.). Oxygen is the next factor. Oxygen catalyzes chemical reactions that lead to rancidity. Rancidity oxidation occurs in fresh, frozen, and dried foods. Removing oxygen in most cases will extend the quality shelf life of foods.
Always use FIFO (first-in, first-out), meaning use your oldest cans first. Before opening, discard any badly dented, bulging, rusty, or leaky cans or jars that have broken seals. Open cans or jars to view and smell contents. When opening, discard any can that spurts. Discard contents (do not taste) if there is a strange odor or appearance. If there is no strange appearance or odor, taste a sample. For added safety, in the case of older canned foods, you may wish to boil the food for 10 minutes before tasting. Discard if there is an off-flavor. High-acid foods may leach metal or metallic flavors from cans if food is left in open cans; move unused portions, to another container, cover and store in the refrigerator. Low-acid foods should be heated to 165° F or boiled for 5 to 10 minutes before eating. Once opened, canned foods may last between a day and a week, depending on the food.
Storage and preventing spoilage
To insure lasting flavor and quality, it is important to store dried foods properly. The essential elements of good storage are COOL temperatures and a DARK, DRY environment.
Do not consume canned goods that have become swollen, dented, or corroded (Red Cross, 2009).
As a general rule, unopened home canned foods have a shelf life of 1 year and should be used before 2 years. Commercially canned foods should retain their best quality until the expiration code date on the can. This date is usually 2 to 5 years from the manufacture date. High acid foods usually have a shorter shelf life than low acid foods. For emergency storage, commercially canned foods in metal cans or jars will remain safe to consume as long as the seal has not been broken. (That is not to say the quality will be retained for that long.) Foods “canned” in metal Mylar®®-type pouches will also have a best-if-used by-date on them. The longest shelf life tested for this type of packaging has been 8 to 10 years (personal communication U.S. Military MREs). Storage for longer than 10 years is not recommended (Bingham et al., 2006).
The best advice in the effective use of a dry goods storeroom is: rotate, rotate, rotate. Date all foods and food containers. Stored foods cannot get any better than what originally went in, but they can certainly get worse. The first food in should be the first food out: FIFO. It takes a bit of imagination and craft to position foods within a storeroom to best implement this principle. Keep a handy and readily visible record of the “use by” and “sell by” dates of the received foods and the shelf life in general.
Keep storeareas cool, dry and well ventilated. The temperature should be between 50°F and 70°F. The cooler, the better. Temperature has more to do with how long well-dried foods store than anything else. The storage lives of most foods are cut in half by every increase of 18°F (10°C). There is probably a limit as to how far this statement can be taken, but a reasonable expectation of shelf life may be extrapolated from room temperature down to freezing. No doubt, the inverse could also be considered true. Cool storage reduces respiratory activity and the degradation of enzymes; it reduces internal water loss and inhibits the growth of decay producing organisms, and in some foods such as fruits and root crops, it slows the production of ethylene, a naturally occurring ripening agent.
As part of maintaining optimal temperature, it is suggested that adequate ventilation should be provided (some air exchange rate is absolutely essential). In addition, the storeroom should be free of un-insulated steam and water pipes, water heaters, transformers, refrigeration condensing units, steam generators or other heat producing equipment.
Ideally, storage areas should have a humidity level of 15% or less. Unless the storeroom is located in the desert, consider air conditioning or dehumidification during the most humid times of the year. A second option is to use moisture impervious packaging. Ideally, there is no reason not to use both.
Maintain stored foods in their original packages whenever possible. Most packaging is designed for the food it contains and will remain in good condition for their given shelf-life in the absence of temperature and humidity abuse. For instance, the cardboard box will help cushion jars and other glass containers from breakage. If original packaging is not practical, maintain the food in airtight containers, primarily to prevent the entry of insect and rodent pests and keep out other contaminants. To take this to another level, consider oxygen as a major threat to the quality of food. The chances are that moisture-proof packaging is also airtight. The less head gas (<2% O2) in a package, the longer its shelf life is maintained.
Avoid storing foods in direct sunlight. Sunlight promotes oxidation and the subsequent loss of the food’s nutritional value and quality. Fat-soluble vitamins, such as A, D, E and K are particularly sensitive to light degradation. It is far better to block sunlight on windows and skylights and rely on artificial illumination for the time the storeroom is in use.
Food Quality and Safety
Keep in mind that most commercially processed foods have a “best if used by” shelf life. This is the date that the manufacturer feels retains the intended quality of their food product. This is especially true for canned and dried foods, since neither of these foods supports microbial growth leading to spoilage or illness. Hence, their product shelf life is determined by quality and not safety. The true shelf life of any safe (dried or canned) emergency food storage item is the time frame you are willing to use that food in an emergency. Even poor quality foods have nearly all of their original nutritional levels. It may taste bad, but may save your life in an emergency.
In contrast to “best if used by” dates is “use by” dates. “Use by” dates are usually food safety issues and should not be exceeded. Foods with “use by” expiration dates should not be used for long-term food storage. Most people are not aware that expiration dates are not required by law. Consequently, there is little oversight of these dates. Some food storage manufacturers list expiration dates of 10, 20, and even 30 years on their products. These dates are rarely scientifically determined and are more of a marketing claim.
Canned foods should not be allowed to freeze. Freezing will bulge cans and may cause seam failures, leading to a potential for foodborne illness. Dry foods and honey can freeze without concern. Oils can freeze and get cloudy. This is natural. They will become translucent again when they warm up.
What NOT To Store!
- Home Canned Butter, especially unsalted, canned butter. (Why? – unsalted canned butter has NO protection from botulism, salted, home canned butter has no science-based process to can safely)
- Petroleum jelly covered raw eggs. (Why? – there is no protection from microbial contamination. This is a major foodborne illness risk)
- Milled Grains (Whole wheat flour, Cornmeal, Cereal, Granola) (Why? – quality deterioration)
- Oily Grains or Seeds (Nuts, Brown rice, Pearled barley, Sesame seeds) (Why? – quality deterioration)
- Home canned Quick Breads (why? – these foods are not safe for home canning)