Bacterial Growth and Reproduction

Bacteria are everywhere! Bacteria have many useful roles, such as making cheese and assisting with digestion in the intestine. Some bacteria can also make people sick. Everyone is at risk of getting a foodborne illness; however, some populations are at greater risk than others, including infants and young children, pregnant women, the elderly, and people with a compromised immune system.

 

Bacteria become harmful when allowed to grow and multiply to numbers that are no longer tolerated by the human body.  This causes a foodborne infection. Some bacteria can also produce a toxin, which acts like a poison in the body. Therefore, if bacteria can be prevented from multiplying to dangerous numbers or producing a toxin, foodborne illness can be prevented.

 

The appropriate environment to support rapid growth and multiplication of bacteria includes:

1. food
2. moisture
3. favorable temperatures

The amount of moisture required and the temperature and type of food needed for growth will vary among different types of bacteria. However, bacteria commonly found in food can be controlled by following safe food handling practices.

When food is not handled correctly, it provides an ideal environment for bacteria growth. Under the right conditions, one single bacterium can grow to trillions in just 24 hours. Bacteria can double in number every 20-30 minutes.

 

In most cases microorganisms use our food supply as a source of nutrients for their own growth.  Bacteria need the right environment to grow, including favorable moisture and pH content, and correct temperatures.

Bacteria have an absolute demand for water.  Without water no growth can occur, therefore, foods with higher water contents, such as meats, are at greater risk for bacterial contamination.

The type of food is also important.  This is best measured by the pH of food or the acid content.  In general, the pH of foods varies, although most are neutral or acidic. However, most bacteria favor a pH near neutral or slightly acidic, such as meat and dairy products.  Foods with a low pH (very acidic) are more resistant to bacteria growth.

Bacteria have ranges of temperatures that promote growth.  They also have maximum temperatures at which they can no longer survive. By controlling the temperature of food, you can control the bacteria content of the food.  Temperature control will be discussed in more detail later in this lesson.

 

Bacteria are everywhere - in many foods, on your skin, under your fingernails, on all kinds of other surfaces, in the soil and on pets.

The most common food sources of bacteria are foods of animal origin, including:

-raw beef, pork, poultry, and seafood,

- eggs, and

- unpasteurized milk.

 

Bacteria occur naturally in many foods, so you should always assume bacteria are present. Generally, they are part of the environment. They may be in the soil or water, or may be part of the animal’s natural flora (bacteria commonly found in the animal’s digestive system). Bacteria can also be introduced by poor food handling practices.