How Fast Can Bacteria Multiply in Food?

Bacteria are small organisms that multiply quickly, and they can be either a good or bad thing when it comes to health and food. When you eat yogurt, for example, the healthy bacteria contained therein can benefit your digestive tract. On the other hand, when you have a picnic and the heat warms your food, bacteria can multiply at a rapid rate and cause illness when you eat the food. Because bacteria can multiply every 20 to 30 minutes, it is important to practice proper food preparation and cooking techniques to prevent people from getting ill.

A woman cleaning the kitchen counter.
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Bacterial Division

Contained within each bacterium is the genetic information that the bacteria needs to produce a new, replicated bacterium. This allows bacteria to multiply exponentially. According to the U.S. Food and Drug Administration, bacterium can double within 20 to 30 minutes, meaning that one bacterium turns into two, then two become four, leading eventually to the formation of millions of cells in a few hours. While millions of cells may be in a food item, it only takes as few as 10 E. coli bacteria to make you sick, so even a small amount of bacteria can be harmful.

Size of Bacteria

The dangers of bacteria in food can be difficult to determine because they are microscopic. An estimated one million bacteria can fit inside one square inch, according to the FDA. Examples of bacteria commonly found in food include salmonella enteritidis, staphylococcus aureus, clostridium botulinum and listeria monocytogenes. And these bacteria can grow rapidly. At 1:00 p.m., a food can have 1,000 bacteria on it. If the bacteria were to grow every 20 minutes, they could number more than 32 million five hours later, according to the health department in Bethel, Connecticut.

Growth Factors

Bacteria on food will not automatically grow. Instead, they must have the right environment that fosters growth. By minimizing these factors, you can prevent bacterial growth that could lead to illness. One example is temperature. The hotter an environment, the more likely the bacteria are to grow. Bacteria are less likely to grow below 40 degrees Fahrenheit and above 140 degrees Fahrenheit, according to the FDA. Nutrients are another factor. Bacteria love to eat protein, which means foods such as meat, poultry, eggs, dairy products and seafood can be a breeding ground for bacteria. Moisture also breeds bacteria. Dry foods are less likely to foster bacterial growth.


To keep bacteria from multiplying quickly, it's important to keep food in the safe zone for temperatures, such as in the refrigerator or the freezer. Cooking food as thoroughly as possible can bring bacteria to a high temperature, killing them. Leaving food out for more than two hours can cause bacteria to multiply to a harmful level. Keeping your hands and cooking surfaces clean can also reduce the likelihood that bacteria will be transmitted. Sanitizing surfaces with bleach or hot water can kill bacteria and reduce contamination.

Is This an Emergency?

If you are experiencing serious medical symptoms, seek emergency treatment immediately.
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