Biology Interview Question:

Why do preserved foods not spoil?

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Plant and animal cells must stay in an isotonic, or neutral, solution to survive. When salt or sugar is added, many of the cells wither and die, and the bacteria cannot live on dead cells.

Sometimes they have agents added that do not allow bacteria and other microbes to colonize and grow on the food. Microbes like bacteria and fungus break down the food causing the spoilage.

There are bacteria and other microorganisms, which live in all sorts of environments. Some tolerate oxygen and some do not. Some tolerate salt and some do not.

There are certain limits or parameters outside of which most or no microorganisms can remain active, however this is theoretical. There have been microorganisms such as Archea living in thermal vents, hot springs, salt lakes, and other extreme environments for ages and ages.

Some microorganisms create "spores" which are like hard seeds, which can survive for many years under harsh conditions, waiting until conditions are right to germinate and become active again. One example of this is Bacillus Anthracis, the bacteria that causes Anthrax.
Submitted by: Administrator