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.