Does the microwave kill all bacteria? It depends

Facts to remember
– The oven actually kills microbes
-But it depends on the food
– Cleaning is still necessary

Microwave ovens a job By emitting electromagnetic waves with a frequency of approximately 2450 MHz. The energy generated by these waves is absorbed by the water, fats and sugars in the food, which then begin to vibrate at a rate of 2.5 million times per second. These vibrations are what generate heat.

However, to destroy bacteria and other microorganisms that may be present in food, the temperature must reach a high enough level. In general, food should be exposed to microwaves for at least 30 seconds, as French researchers confirmed in 2018 in Book chapter About preserving foods using microwave ovens

Effective in killing germs

The French authors added that several studies have in fact shown that heating food in a microwave oven makes it possible to pasteurize or even sterilize it. This method will be as effective as using a water bath.

in Study published in 2019Researchers in Malaysia intentionally contaminated various types of food with bacteria, then reheated those foods in the microwave. They observed a significant decrease in survival after 30 to 40 seconds of exposure. All microorganisms were inactivated after 60 seconds. For fatty foods, only 50 seconds were needed, perhaps because the temperature of the fat rises more quickly.

according to Researchers from BangladeshA microwave oven may also be useful in making contaminated foods safe for consumption. In 2020, they collected street foods (chicken sandwiches, pizza, chicken pot pie, pasta and sausages), most of which contain disease-causing bacteria. By heating these foods for one minute in the microwave, I was able to significantly reduce bacterial contamination.

But uneven cooking

However, the effectiveness of this oven in killing bacteria is not without drawbacks. In fact, microwaves only penetrate 2.5 to 4 cm into the food. Confirms United States Food Safety and Inspection Service. Therefore, when the food is large, the microwaves will be completely absorbed before they reach the center: this was also confirmed by the French researchers.

Therefore parts that do not pass through microwaves will not be reheated. The temperature there will only rise as heat spreads from outside to inside. This means you have to cook food with less energy for longer, so you don't overcook the outside of the food. Additionally, if the food is made up of several different materials, the heat will not spread evenly.

The French researchers explained that in the end, we can sometimes notice a difference of 20 degrees Celsius between different food areas. The bacteria present there can survive. This may be a problem when cooking meat, poultry, fish and eggs. The American agency also suggests using a cooking thermometer and measuring the temperature in several places in the food before eating it.

Is the oven Sterile?

However, just because a microwave can destroy bacteria doesn't mean it doesn't need to be cleaned well. Some microorganisms can survive in extreme conditions.

In 2024, Spanish researchers I wondered if a microwave oven could harbor these resistant microorganisms. They sampled, among other things, 10 microwaves located in the residences and 10 in common areas, such as the cafeteria.

They identified several different genera of bacteria, including Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes. These microorganisms usually live on our skin and are therefore found on frequently touched objects.

The researchers also identified some bacteria known to cause foodborne infections in humans. Many of the bacteria detected were associated with food and usually contaminate food. Some may pose health risks due to their pathogenic properties and resistance to antibiotics.

In other words, These bacteria are no different The kind you find on the kitchen counter. Therefore, their presence in microwave ovens reminds us of the importance of cleaning these appliances properly, like any other item in the kitchen.

Judgment

Microwaves can be used to cook food and destroy any bacteria that may have gotten into it. However, since cooking is not uniform, some foods may require special precautions. Microwaves can also contain some heat-resistant bacteria if they are not cleaned properly.