Microwaves are a convenient kitchen appliance for reheating leftovers and cooking food quickly. But can they also kill germs like bacteria and viruses in food? The answer is yes, microwaving food can kill germs, but it’s not always straightforward and depends on several factors.
The Science Behind Microwaving and Germs
Research indicates that microwaves can be effective at reducing germs, but the process is not always uniform. A well-known study in 2007 from the University of Florida highlighted the ability of microwaves to sanitize sponges. This study found that microwaving a wet sponge on high power for two minutes eliminated 99% of pathogens. However, a more recent study in 2017 suggested a nuanced perspective. While microwaving might kill weaker bacteria, it could potentially favor stronger bacteria, leading to them becoming more dominant. Despite this, experts generally agree that microwaving does help in reducing harmful germs, although it might not guarantee a perfect 99% germ-free environment, and effectiveness can vary depending on the type of pathogen.
It’s important to understand that microwaves kill germs primarily through heat, not microwave radiation itself. Similar to cooking methods like baking or frying, microwaving raises the temperature of food, and this heat is what deactivates bacteria and viruses. The required temperature to kill germs varies depending on the specific type of microorganism.
Uneven Heating in Microwaves: A Key Challenge
A significant challenge with using microwaves for killing germs is their tendency to heat unevenly. Anyone who has reheated food in a microwave has likely experienced hot spots and cold spots. This uneven heating means that while some parts of the food might reach temperatures high enough to eliminate germs, other areas might not. Consequently, microwaving may only partially disinfect food items.
How to Effectively Kill Germs in Food with a Microwave
While the FDA doesn’t endorse microwaves for sterilizing medical devices, including household items like thermometers, you can still use your microwave to sanitize food and certain other items effectively.
For sanitizing non-food items like baby feeding supplies, the CDC recommends a steaming method in the microwave. This method is suitable for items that have already been cleaned with soap and water, such as baby bottles, syringes, medicine cups, and spoons.
- Clean the items: Thoroughly wash the items with soap and water first.
- Prepare for microwaving: Place disassembled items in a microwave steaming system or a glass or ceramic container with a lid and some water to create steam.
- Microwave on high: Heat the items on high power for 4-6 minutes. The CDC suggests that most germs are killed after six minutes of steaming.
- Air dry: Allow the items to air dry completely before reuse or storage.
To sanitize food or liquids in the microwave, especially takeout food where contamination is a concern, the key is to ensure the food reaches a uniformly high temperature capable of killing germs. This method is intended for potentially contaminated food, not for spoiled food.
- Prepare the food: Wipe down takeout containers or transfer food to microwave-safe, sterile containers.
- Microwave on high: Cook the food or liquid in the microwave on high power. Cooking time will vary based on the type and amount of food.
- Check the temperature: Use a food thermometer to verify the internal temperature. It should reach at least 170°F (77°C) throughout. Check in multiple locations and stir the food to distribute heat evenly.
Items You Should Never Microwave
Microwaves are designed for heating food and beverages. It’s crucial to only microwave items intended for microwave use. Certain materials should never be microwaved as they can pose fire hazards or cause explosions.
Avoid microwaving these items:
- Metal of any kind or amount
- Sharp objects like toothpicks (especially with metallic decorations)
- Whole eggs in their shells
- Thin or flimsy plastics that are not microwave-safe
- Paper products like brown bags or newspapers
- Foam insulated containers
- Styrofoam
- Plastic bags
- Clothing and large fabric items
Microwaving Masks and Toothbrushes: Not Recommended
Disposable medical masks are designed for single use, and attempting to sanitize them in a microwave is not recommended. The heat can damage the mask material, reducing its effectiveness. Health experts and the FDA advise against reusing disposable surgical masks.
Similarly, while some might consider microwaving toothbrushes for sanitization, there’s no evidence to suggest that using your own toothbrush after being sick poses a re-infection risk if you rinse it after each use and don’t share it. Furthermore, microwaving a toothbrush can damage it.
Heat is Key to Germ Reduction
Heat is a powerful tool for destroying germs, including bacteria and viruses. Microwaves generate heat and can be used to sanitize and disinfect items, including food, to some extent. However, it’s important to be aware of the limitations, particularly uneven heating. More research is needed to provide definitive guidelines for using microwaves for sanitization purposes. Understanding these basics will help you make informed decisions about whether microwaving is the appropriate method for your germ-killing needs.
