Does Microwave Kill E. Coli?


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You may get infected with E.coli if you eat contaminated foods, such as raw milk or undercooked meat products. Normally, you can cook or use heat treatment to destroy or reduce the number of foodborne pathogens, including E.coli, in your food. But can microwaving your food deliver the same effect? Let’s find out.

Studies showed that microwave heat can destroy harmful germs in food, including E. coli, as long as the food reaches a safe minimum temperature of at least 160°F or 70˚C. People should also observe microwave food safety practices to make sure their food is bacteria-free and safe to eat.

Here is everything you need to know about the microwave’s potency in killing E.coli.

What is E. coli?

E. coli or Escherichia coli is a type of diverse bacterial group typically found in the environment, foods, and your intestines.  

Most strains of E. coli are considered harmless. They live in your intestine and even contribute to your gut health. However, there are also strains that can make you ill. [01]

Some types of E. coli may even result in diarrhea, UTI, respiratory disorder, pneumonia, and other diseases.

According to FoodSafety.gov, E. coli is one of the primary bacteria that lead to many foodborne illnesses, hospitalizations, and deaths in the United States.

One of the most dangerous strains of E.coli is the Shiga toxin-producing E. coli or STEC. It is also referred to as enterohemorrhagic E.coli or verocytotoxic E.coli. [02,03]

STEC can infect people of all ages, from very young kids to the elderly. People who are more vulnerable to E.coli infection include children younger than five years old, those who are 65 and older, those who travel to some countries, and those with compromised immune systems, including pregnant women.

Once infected with STEC, you may get symptoms like diarrhea, severe stomach cramps, and vomiting. 

While most people will get better within 6 to 8 days, others may experience more severe or even life-threatening reactions.

The Centers for Disease Control and Prevention reported that about 5% to 10% of people diagnosed with STEC infection develop a potentially deadly complication called hemolytic uremic syndrome or HUS.

Symptoms of HUS include:

  • Reduced urination frequency
  • Feeling extremely tired
  • Losing pink color on cheeks and the inner side of lower eyelids

Terrifying, isn’t it?

But how exactly can you be infected with E. coli?

According to the US Food and Drug Administration, various types of E.coli can contaminate a wide array of foods and water.

In the past, outbreaks of E. coli in the United States have involved raw milk and cheese, sprouts, leafy greens, and raw beef and poultry.

What’s even more horrifying is that these bacteria can grow slowly in your refrigerator and can even survive in acidic food products, including mayonnaise and apple cider.

✅ Cooking with Microwave? Check out these 25 Genius Time-Saving Kitchen Gadgets

Does microwave kill E. coli? 

Now that you realize how scary E. coli can be, let’s get down to the main topic.

Can your home microwave destroy E. coli from your food?

Here’s what the health authorities and studies found.

The CDC stated that home-type microwave oven with 2.45 GHz can inactivate mycobacteria, viruses, and bacterial cultures within the range of 60 seconds to 5 minutes. Still, a high-powered microwave can disinfect better.  [04]

One study published in the Journal of Clinical Microbiology reported that microwave killed clinical isolates, which include E. coli, S. aureus, S. enterococcus, S. epidermidis, S. marcescens, P. mirabilis, P. aeruginosa, and P. vulgaris, within 5 minutes of exposure. [05]

Another study released in the Journal of Hospital Infection also confirmed this finding.

The study found that vegetative strains of bacteria like E.coli in aqueous suspensions were swiftly killed within 5 minutes or less by microwaves of 2.45 GHz frequency with 325 W and 650 W power settings. [06]

A study reported in the Journal of Environmental Health by researchers from the University of Florida also found that microwaving a sponge at 100% power level destroyed more than 99% of the total bacterial count within a short 1 to 2 minutes, and it took only 30 seconds to kill E.coli. [07]

In addition, researchers from the University of Wisconsin-Madison conducted a study investigating the disinfection effect of microwave ovens on household cutting boards which were inoculated with E. coli or other bacteria in broth culture. [08]

The study, which was published in the Journal of Food Protection, suggested that brief cooking of wooden boards under high settings in the microwave oven is effective in killing bacteria and can be a simple yet inexpensive technique to protect your food from cross-contaminating pathogens.

Nevertheless, while microwaves can indeed kill E. coli, they have one major drawback: uneven heat distribution.

Why is this important? 

Because the primary killer of E.coli and other germs in the microwaves is not radiation (which most people often thought), but the heat.

The microwave generates radio-frequency waves that make water molecules in your food to vibrate. This vibration, in turn, results in friction that enables your food to heat up to a safe temperature that can destroy bacteria.

The problem is that your microwave can’t distribute the heat evenly across all surfaces of your food, resulting in the so-called cold spots, areas where harmful germs like E.coli remain alive.

So the key to killing E.coli and other germs in the microwave is to make sure every part of your food is heated to a certain temperature (more on this below).

Is E. coli killed by heat? At what temperature can you kill E. coli?

Heat can kill E.coli and other foodborne pathogens. However, foods need to be heated to the recommended safe internal temperatures. E. coli began to denature at 40˚C or 104°F and die off at 70˚C or 160°F.  [09,10, 11]

Thus, if you want to make sure your food is free of E.coli,  be sure to cook your food thoroughly to at least 160°F. [12]

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How to kill E. coli in the microwave effectively?

Since microwaves do not heat food evenly, food and health authorities, including CDC, FDA, USDA FSIS, and Foodsafety.gov, recommend using a food thermometer like this one or oven temperature probe like this one to make sure every part of the food reaches a safe minimum internal temperature. [13]

Here’s the FoodSafety’s guideline on safe minimum cooking temperatures and recommended rest time for some common foods.

Types of Food

Safe Internal Temperature (°F)

Meat mixtures and ground meat of beef, lamb, and veal

160

Meat mixture and ground meat of turkey and chicken

165

Steaks, roasted, or chopped fresh beef, lamb, and veal

145

Rest time of 3 minutes

All sorts of poultry

165

Casseroles and leftovers

165

Eggs

Cook until the white and yolk are firm

Egg dishes like frittata

160

Fishes with fins

145 or cook until their fleshes are opaque and can be easily separated with a fork

Lobster, scallops, shrimp, and crab

Cook until their fleshes are opaque and white

Oysters, clams, and mussels

Cook until their shells are opened

You should also rotate and stir food in the microwave for uniform heat distribution.

Covering your food properly in the microwave can also help distribute heat evenly across your food.

Learn more about the benefits of covering your food in the microwave here.

More effective ways on how to prevent E.coli infections and other foodborne illness in your home

Apart from relying on the microwave heat to kill E.coli in the food, you should also practice food safety habits when preparing your food to avoid cross-contamination.

The CDC outlines the following practices to stop E.coli infections:

  • Before handling food, wash your hands thoroughly with running water and soap
  • Follow CDC’s 4 steps to food safety: clean, separate, cook, chill
  • Use a food thermometer to ensure the meat reaches safe cooking temperature. Be sure to check the temperature of the thickest part of the meat
  • Avoid cross-contamination by thoroughly washing cooking tools and utensils with water and soap after using them to handle your meat
  • Never drink untreated water or swallow water when playing or swimming in bodies of water like swimming pools, ponds, lakes, and streams
  • Don’t consume raw batter or dough
  • Drink only pasteurized juices and milk
  • Be careful with the food and water you pick when travelling outside the country

Does putting a sponge in the microwave kill germs?

One study released in the Journal of Environmental Health found that microwaving sponges and pads at full power for 2 minutes effectively killed over 99% of living germs and the spores of bacteria in them. Make sure the sponge is wet and not dry. Still, microwaves are not the best disinfectant.

Do microwaves sterilize?

While conventional microwaves in the market can be utilized for high-level disinfection, they are not suitable for sterilization, according to researchers. CDC also noted that microwaves used for medical devices sterilizations have yet to be cleared by the FDA.

Eina Aivoges

Eina Aivoges is a certified health and wellness coach and a licensed medical laboratory scientist. She's also a foodie, avid coffee drinker, cat-lover, blogger, and traveler.

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