Monday, May 14, 2012

Important Temperatures for Food Safety

Temperature is one determining factor in the safety of home preserved foods.  Most bacteria, molds, and yeasts grow best at room temperature.  As temperature is decreased, the activity of bacteria is slowed down.  As temperature is increased, an increasing number of bacteria are killed. 

 Processing foods in a boiling water bath will kill most bacteria, molds and yeasts.  However, in an attempt to survive under stressful conditions, some bacteria will produce spores, a seed-like product, that can survive the temperature of boiling water.  When temperature and growing conditions improve, these spores can germinate producing a toxin.  This is especially dangerous in the case of Clostridium botulinum which produces a toxin that affects the central nervous system and may cause death.  Besides its need for room temperature, Clostridium botulinum needs a low acid environment in the absence of oxygen in order for its spores to produce this deadly toxin.  Canned vegetables and meats provide that environment.  That is the reason for using a pressure canner to process low acid foods.  Pressure will increase the temperature inside a canner to above the boiling point of water.

Note that the temperatures described below are based at sea level.  As altitudes increase, it is necessary to increase the length of processing time to process foods in a boiling water bath and to increase the pounds pressure in a pressure canner. Below are important temperatures and temperature ranges to be aware of.

240ºF. — Bacterial spores are destroyed in low-acid foods
240ºF. — Low acid foods processed in pressure canner at or below 1,000 feet
212ºF. — Boiling point of water.  Processing temperature for high acid foods in boiling-water bath at or below 1,000 feet
180-212ºF. —  Temperature at which molds, yeasts, and some bacteria are destroyed in acid foods
140-180ºF. — Growth of bacteria, molds, and yeasts slowed, but may allow survival of some microorganisms
40-140ºF. — Active growing range of molds, yeasts, and bacteria
50-70ºF. —Storage temperature for home canned and dehydrated foods
32ºF. — Growth of some bacteria, yeasts, and mold slowed
0 to -10°F. — Ideal freezer temperature