Figure 1-5. Growth curve of microorganisms.
(1) During a period of one to several hours, there is a lag phase in which
there is little or no increase in cell numbers. During this phase, the cells are becoming
adjusted to a new environment.
(2) The log (logarithmic) phase is a period of rapid growth. The growing
cells divide and continue to do so at regular intervals until maximum growth can be
supported. In this phase, the microorganisms are well adjusted to their environment
and are able to multiply rapidly.
(3) The stationary phase is one in which the population remains unchanged.
The rate of reproduction equals the death rate in this phase.
(4) The decline (death) phase occurs when the death rate exceeds the rate
b. Ways to Lengthen the Lag Phase. Growth control is important in food
preservation. Prevention or delaying food spoilage is accomplished by lengthening the
lag phase as much as possible. This can be done in several ways:
(1) By the introduction of as few spoilage organisms as possible, that is by
reducing the amount of contamination. The fewer organisms present, the longer the lag
(2) By avoiding the addition of actively growing organisms, which may be
growing on unsanitary containers, equipment, or utensils with which food comes in