Does reheating food kill bacteria?

In this article, we answer the following question: Does reheating food kill bacteria? We will also learn what happens to bacteria when food is reheated and we will give you some tips for reheating food safely.

Does reheating food kill bacteria?

In most cases, yes, reheating food will kill bacteria. However, it is important that the effectiveness of this method will depend on several factors like the type of bacteria, their initial abundance, the heating temperature and duration and the type of food.

Heat has been shown to damage bacterial cell walls and other structures that make them die (1-3). Nevertheless, there are some bacteria that can survive and keep growing in the food when it is not reheated properly (4).

Surprisingly, there are some bacteria that produce spores that are resistant to heat and need higher temperatures to be destroyed (5). Those spores can later contaminate the food even if the original bacteria were killed during the initial reheating process (5).

So, be sure that you use a proper reheating method to minimize the risk of contamination by bacteria! You have to take foodborne illness seriously!

What temperature is needed to kill bacteria when reheating food?

You should reheat food to an internal temperature of at least 167°F (75°C) to be sure that most of the harmful bacteria have been killed (6-7). This is in fact the temperature that is recommended by the United States Department of Agriculture (USDA) and the Food and Drug Administration (FDA) to ensure food safety (6-7).

Several harmful bacteria like Salmonella, Eschericia coli, and Listeria are killed at this temperature (6-7). However, other types of bacteria could handle this temperature (8) and other parameters like the initial abundance and the type of food should be considered as mentioned before.

Always use a thermometer to check the internal temperature of your reheated food to guarantee that the entire food reaches the appropriate temperature. Thus, it is important that you prevent cold spots where bacteria can survive and later contaminate the entire food.

If you are using a microwave, be sure that you are always rotating and stirring your food to guarantee that it heats evenly throughout! do it also for a long time!

How long should you reheat food to ensure that bacteria are killed?

You should reheat your food for at least 2 minutes once it reaches an internal temperature of 165°F (75°C) to be sure that most of the harmful bacteria have been killed (6-7).

As mentioned before, it is recommended that you always use a thermometer to measure over time the internal temperature of your food while reheating. If you are not sure, it is always better to keep it for a longer time in the microwave or your selected heating appliance. 

The time required to reach the appropriate temperature will depend on different factors like the type of food, its quantity, and the power of the heating appliance that you are using.

It is very important that you know that reheated food is considered a high-risk food, so you should take special precautions. Be sure that your food never leaves the danger zone (50–60°C) for more than 4 hours before or after reheating (6-7).

Be sure to follow these instructions and the recommended guidelines (6-7) to reduce the risk of foodborne illness.

What are some common types of bacteria found in leftover food?

Different species of bacteria can be found in food leftovers (9). The types and their abundance will depend on the way you prepared your food, the type of food and how it was previously stored.

The three most common types of bacteria isolated from leftover foods are:  

  • E. coli: This bacterium has been shown to cause severe illness, including kidney failure (10). It has been frequently identified in undercooked meat (11) , unpasteurized juice and milk (12), and contaminated water (13).
  • Salmonella: This bacterium could lead to food poisoning and is commonly found in raw or undercooked poultry, eggs, and meat (14).
  • Listeria: This bacterium can also cause severe illness, especially in pregnant women, the elderly, and people with weakened immune systems (15). It has been frequently isolated from meat, soft cheeses, and unpasteurized milk (15).

To avoid any type of foodborne illness from your leftover food, be sure that you reheat your food at the recommended temperature. Discard any food that has been out for too long!

What are the risks of consuming food that has not been reheated properly?

The main potential risks of eating food that has not been reheated properly are gastroenteritis, food poisoning, and salmonella infection (4-9). Their symptoms can include diarrhea, abdominal pain and cramps, nausea, and vomiting (4-9).

In some cases, you can also get botulism, which is a rare but serious form of food intoxication attributed to a toxin (botulinum neurotoxin) produced by the bacteria Clostridium botulinum (16).

Eating food that was not properly reheated could expose you to hepatitis A, a viral infection transmitted through contaminated food (17).

Be aware that you can reduce the risk of getting these diseases by following recommended food safety guidelines, which include not only reheating your food properly but also by correctly storing and handling your food. 

What are some tips for reheating food safely?

The following tips will help you to reduce the risk of foodborne illness when reheating food:

  • Use a food thermometer: As mentioned before, a food thermometer will help you to make sure that the internal temperature of the food reaches the recommended temperature required to kill any harmful microorganism.
  •  Don’t reheat food more than once: If you do that, you are increasing the risk of bacterial growth and subsequent foodborne illness.
  • Reheat food in small portions: This will help you to be sure that your food heats evenly and thus avoid the risk of underheating leaving a cool place for bacterial proliferation. You can also heat evenly throughout by rotating or stirring your food, especially in the microwave.
  • Finally, it is important that you reheat your leftovers promptly. It is best to reheat within two hours of removing your leftovers from the refrigerator and be sure that you refrigerate them within two hours after cooking it.


In this article, we answered the following question: Does reheating food kill bacteria? We also talked about what happens to bacteria when food is reheated and we provided some tips for reheating food safely. 


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