Editing Canning (section)

=== Microbial control ===
To prevent the food from being spoiled before and during containment, a number of methods are used: pasteurisation, boiling (and other applications of high temperature over a period of time), refrigeration, freezing, drying, vacuum treatment, antimicrobial agents that are natural to the recipe of the foods being preserved, a sufficient dose of ionizing radiation, submersion in a strong saline solution, acid, base, osmotically extreme (for example very sugary) or other microbially-challenging environments.

Other than [[Sterilization (microbiology)|sterilization]], no method is perfectly dependable as a preservative. Sterilization is done after the can is sealed, so that both the container and the food are secured.

The spores of the microorganism ''[[Clostridium botulinum]]'' (which causes [[botulism]]) can be eliminated only at temperatures above the boiling point of water. As a result, from a public safety point of view, foods with low [[acidity]] (a [[pH]] more than 4.6) need sterilization under high temperature (116–130&nbsp;°C). To achieve temperatures above the boiling point requires the use of a [[pressure cooking#Related devices|pressure canner]]. Foods that must be pressure canned include most [[vegetable]]s, [[meat]], [[seafood]], [[poultry]], and [[dairy]] products. The only foods that may be safely canned in an ordinary boiling water bath are highly [[acid]]ic ones with a pH below 4.6, such as [[fruit]]s, [[pickling|pickled]] vegetables, or other foods to which acidic additives have been added. Although an ordinary boiling temperature does not kill botulism spores, the acidity is enough to stop them from growing.<ref>{{cite web|author=William Schafer |url=http://www.extension.umn.edu/distribution/nutrition/DJ1097.html |title=Home Canning Tomatoes |publisher=Extension.umn.edu |date=9 January 2009 |access-date=2010-07-14 |url-status=dead |archive-url=https://web.archive.org/web/20100701144442/http://www.extension.umn.edu/distribution/nutrition/dj1097.html |archive-date=1 July 2010 }}</ref>