d. The bacteria that cause foodborne disease reproduce and grow In the
temperature range of 45F to 140F. This range is called the temperature danger
zone. Notice that the danger zone temperatures include normal room temperatures.
Bacteria producing foodborne diseases grow rapidly at room temperatures.
e. Knowing how temperature affects bacterial growth is critical in keeping food
safe. Generally the dangerous bacteria grow more slowly at lower temperatures. They
grow most rapidly at and somewhat above room temperature. When the temperature
reaches 140F, most will die off.
1-11. TIME REQUIREMENTS FOR BACTERIAL GROWTH
a. Given enough time, most bacteria can adjust to different foods, temperatures,
or various degrees of acidity.
b. The growth pattern of a bacterial colony can be divided into four distinct
phases: the slow phase, the rapid growth phase, the equal phase, and the death
(1) The slow phase occurs when bacteria are introduced into a new
environment and must adapt to the new conditions. This adjustment is complete in
about 4 hours. The slow phase is also called the lag phase.
(2) After the bacteria have adjusted to the new environment, they will grow
rapidly, increasing tenfold for every unit of time. This period of accelerated growth is
called the rapid growth or log phase.
(3) Eventually, the bacteria multiply to such an extent that they begin to
compete with each other for food and space. They no longer increase so quickly.
Finally the growth of new bacteria equals the death of old bacteria. This period is called
the equal or stationary phase.
(4) The death phase takes place when more bacteria die than are
reproduced. This occurs due to lack of food and the accumulation of waste products.
Eventually all the bacteria celIs die. The death phase Is also called the decline phase.
Figure 1-2 shows these phases in graphic form.