Affecting Harmful Levels of Pathogens

Affecting Harmful Levels of Pathogens

Time and temperature are two variables that can affect the overall freedom from harmful levels of pathogens. The disease-causing microorganisms found in food need to be present in significant quantities in order to make someone ill after consuming it. Once pathogens have established themselves in a food source, they will either thrive or be destroyed, depending upon how time and temperature are manipulated.


There are pathogens that can live at all temperature ranges. For most of those capable of causing food borne illness, however, the most friendly environment provides temperatures within a range of 4 to 60oC (40 to 140oF). They are usually destroyed at temperatures above 60oC. Storage at temperatures below 4oC will destroy some pathogens; the cycle of growth and reproduction will be slowed or interrupted in others.


When conditions are favorable, pathogens can grow and reproduce at an astonishing rate. There are four distinct stages of bacterial growth. The first is the lag phase, during which newly introduced bacteria become adjusted to their environment. During the accelerated growth phase, the bacteria reproduce rapidly. Bacteria reproduce asexually; as each bacterium grows, it will split into two bacteria of equal size. Under ideal circumstances, each bacterium can reproduce every 20 minutes. One bacterium could produce 72 million bacteria in just 12 hours.

The growth phase leads to the stationary phase. This is a plateau, during which the rate of growth and reproduction is matched by the rate of elimination. At this point, there is no increase in the number of bacteria. Finally, there is the decline phase. Now, the essential elements for life are exhausted. The elimination rate exceeds the growth rate.

The time during which foods remain in the danger zone is one of the most critical to the prevention of contamination through food borne illness.

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