When we think of long-term food storage, it is often easier to focus on the storage of dry foods. Dried foods often pack the most nutrients into the smallest amount of space. They don’t often, however, provide a well-balanced and tasty diet for long-term survival. For the long-term storage of wet foods, canning is the right answer.
Industrial Canning vs. Home Canning
As modern consumers, we can purchase an incredible variety of foods packaged in durable metal containers. Alternatively, we can grow (or purchase) fresh foods and “can” them ourselves in glass jars with relatively simple equipment. Both options are good, depending upon your skills, interests, and funding.
Canned Food Shelf Life
Commercial canned foods will be labeled with a date that the food should be “best” before. That doesn’t mean the food is inedible after that date, it only means that the manufacturer doesn’t stand by the appearance or flavor after that date. With most commercially canned foods, if they look edible and they smell edible, they are edible. However, throw out any cans which are bulging or leaking — without attempting to smell them.
Manufacturers normally label canned foods to be eaten within 1 to 5 years. Sir John Franklin abandoned some canned food in the Arctic during Franklin’s Lost Expedition in 1845. The contents were edible and nutritious when they were opened in 1939, and that was with the primitive solder-sealing methods of the 19th century. The steamboat Bertrand sank in the Missouri River in 1865. When canned food from the wreck was tested in 1974, it was still safe and nutritious — though it’s smell and flavor had deteriorated.
Home “canned” foods have a “best before” shelf life of one year and should be used within two years. However, after two years, the contents are still usually edible and nutritious.
Oxidation will turn some canned foods darker than their normal color. Chemical breakdown may cause canned foods to be softer than you would expect. Neither of these mean that the canned food is inedible or lacking in nutrition. If you are worried, boil the food for five to ten minutes before tasting it.
The most dangerous bug that can infect improperly canned food — and sicken or kill you — is Clostridium Botulinum. This is the nasty little bug which, under anaerobic conditions, produces the botulinum toxin which causes botulism. “Anaerobic” means without air. Our very act of removing the air from our food containers — to prevent other types of spoilage — is what enables Clostridium Botulinum to produce it’s deadly poison.
Boiling Water Canning vs. Pressure Canning
Clostridium Botulinum cannot thrive in a highly acidic environment. If you are canning foods with a pH of less than 4.6, you can use a simple boiling water canner to preserve the food. High acid foods include items such as:
- Fruits (most)
- Jelly, Jam, Marmalade, and Fruit Butters
With these highly acidic foods, all you need to do is to heat the food to the boiling temperature of water (212°F/100°C at sea level) to kill off the lesser bacteria, yeasts, and molds.
On the other hand, Clostridium Botulinum can thrive in a more friendly low-acid environment. Foods with a pH of more than 4.6 require you to use a pressure canner to heat the food to 250 °F / 121 °C. A pressure canner allows you to raise the temperature of water above it’s normal (sea level) boiling point. This enables you to kill off even the hardy Clostridium Botulinum. Low acid foods include items such as:
- Meat, Poultry, and Seafood
- Vegetables (most)
The National Center for Home Food Preservation offers a free online course: Preserving Food at Home: A Self-Study. The course covers:
- Introduction to Food Preservation
- General Canning
- Canning Acid Foods
- Canning Low-Acid Foods