The basic principles of canning have not changed
dramatically since the 1800s when the first process of food canning was
developed. Heat sufficient to destroy microorganisms is applied to foods packed
into sealed or "airtight" containers. The canned foods are then
heated under steam pressure at temperatures of 240-250° Fahrenheit (116-121°
Celsius). The amount of time needed for processing is different for each food,
depending on the food's acidity, density and ability to transfer heat.
There are two safe ways of processing food, the boiling
water bath method and the pressure canner method:
The boiling water bath method is safe for tomatoes, fruits,
jams, jellies, pickles and other preserves. ...
Pressure canning is the only safe method of preserving
vegetables, meats, poultry and seafood. The Pressure canning Method can be
adopted within three main packages, Tin Cans, Jars and retort pouches (not Mylar).
Dry canning is also widely used to store dry foods with the
addition of oxygen absorbers however with the development of modern plastics
packaging technology most people use Mylar bags.