Biological Changes in Food

Microorganisms, including bacteria, yeasts, and molds, are the prime biological factor involved in food spoilage. These tiny organisms need food to survive just as people do, so food is a natural target. The most common foods spoiled by bacteria include meat, eggs, milk, and opened canned goods.

The naturally occurring yeasts in the air are found almost everywhere, but normally pose no threat. The moisture in foods, however, can encourage their growth to a point that becomes unacceptable. Yeasts prefer high-sugar foods such as fruits, vegetables, and fruit preserves, and can cause unwanted fermentation of fruits and fruit juices in the presence of the proper amounts of exygen, moisture, and acidity (PH). Any method that keeps the moisture content low will be successful in their control.

These microorganisms, like yeasts, prefer high-sugar foods, but are particularly drawn to cheese and bread. The appearance of their bloom on foods indicates that spoilage has begun. Molds are easily spread through the air, are very resistant to drying, and can be difficult to control by the means used for bacteria and yeasts. Commercial food enterprises sometimes use vacuum pumps to remove oxygen from containers, because molds cannot grow in its absence.

There are many weapons in the arsenal with which to fight food spoilage resulting from microbial action, including boiling, refrigeration, drying, and curing with high concentrations of sugar or salt.