Which conditions favour multiplication of bacteria

This is known as the danger zone as it is dangerous for some foods to be in this temperature range for prolonged periods of time. Moisture — Bacteria need moisture in order to grow. This is why they grow on foods with high moisture content such as chicken. Foods that are dehydrated or freeze-dried can be stored for much longer as the moisture has been removed. The state of Florida takes no responsibility for a link's operation or content. The links that are shown are not an exclusive listing of organizations available within the state.

Skip to Main Content. Close alert. They choose different media depending on the preference of the bacterium they wish to grow. Approximately 70 percent of a bacterial cell is composed of water. Complex multi-cellular organisms, such as humans, can ingest their own water.

Single-celled bacteria lack that ability, so they must rely on finding enough available water in their environment to through their cell membranes.

Many bacteria can survive for extended periods without moisture, but without it they can't grow and reproduce. Outside of nutrients and water, each species of bacteria has a specific environmental preference. Preferences include the best pH, temperature range, amount of light, concentration of gases such as oxygen and carbon dioxide, and amount of pressure present. The pH conditions may be acidic with pH levels from 6 to 1; alkaline with pH levels from 8 to 14; or somewhat neutral with a pH of around 7.

Many bacteria grow well at or near a neutral pH of 6. Most TCS foods provide the ideal pH for pathogens. Acidic foods i. Although some species of bacteria have adapted to survive in extremely hot or cold environments, almost all pathogens can grow between 41 o F o F, most with optimum growth around human body temperature Proper refrigeration of food can slow the growth rate of pathogens, and freezing can stop growth altogether.

Refrigeration and freezing, however, do not kill pathogens. There is a short period of time after pathogens are introduced to a food during which they acclimate to the environment. If conditions are ideal, rapid growth will then begin.

The growth rate of bacteria varies by strain, but in general, populations can double every minutes.