The microwave is a marvel of modern technology. Food can go from ice cold to blazing hot in a matter of seconds. It cuts down on cook time, speeds up prep time, and all around makes the home cook’s job easier.
But not everything in your fridge or pantry should go into a microwave. Some foods, beverages, and containers can release toxins, burn, melt, or even explode if they’re nuked for less than a minute. Some may even turn toxic.
A few of these foods are fairly common—you may have even heated one in the microwave this morning. Just because something bad hasn’t happened doesn’t mean it won’t, however, so protect yourself and others in your kitchen by keeping these foods away from the hot box.
Red hot, orange, or green, peppers contain a compound called capsaicin that gives them their kick. When peppers are heated, especially the ultra-hot varieties, the capsaicin in them vaporizes into the microwave’s enclosed air. Opening the microwave door exposes you to fumes that can irritate and burn your lungs, throat, eyes, and nose.
How to heat: Roast, sauté, or grill peppers instead of putting them in the microwave.
You’re tired of cold eggs for your mid-day snack, so you pop one into the microwave for 15 seconds. All seems well until you cut into the egg and it explodes—all over your office, your computer, and you.
As eggs both in the shell and those that are peeled are heated in the microwave, they release steam. The steam cannot escape the whites, so pressure builds. When you cut‚ or worse, bite‚ into the egg, the steam is released instantly. The resulting explosion may burn you.
How to heat: If you want to heat up eggs for a salad, snack, or toast topper, you can slice one into fourths and gently heat in the microwave. If you have a few minutes, pop one into a cup of hot water, and let it sit 3 to 5 minutes.
Food-safe foam is a type of plastic. When heated, it can release harmful chemicals into your food and into the air. Foam is also not heat stable when shot through with microwaves. It might melt or warp.
How to heat: Place foods on a glass plate or container instead of cooking in the styrofoam. Cover with a paper towel, and microwave as normal.
Takeout containers with handles
The handled carry-out containers have metal, and metal inside a microwave is a no-no. When heated, the metal could spark, causing a fire.
As a rule of thumb, double check that any plastic container is says "Microwave Safe" on it before you zap it. This label is regulated by the FDA and will tell you whether or not you'll risk exposure to chemicals if the container is heated.
How to heat: Empty the leftovers onto a microwave-safe container or plate. Top with a paper towel to block splatters and pops. Heat normally.
Mug of water
It’s much faster to heat water for tea in your microwave than to wait on a kettle to boil, but the time savings could cost you dearly. Water that is heated by itself in a microwave can quickly become superheated. That means, though you see no rolling bubbles, the water is exceptionally hot. Add a tea bag, spoon, or even just move the water, and it could begin to boil at once. It might even explode.
How to heat: Let a kettle do the work. If you don’t have a stove eye readily available, consider an electric option.
Don’t be tempted to top your oatmeal with a handful of grapes and heat them before diving in for your morning meal. Grapes become superheated in the microwave, and the sugary pulp quickly turns into molten plasma. They could explode in the microwave, while you’re stirring, or even when you take a bite, sending ultra-hot fruit flying.
How to heat: If you want to heat grapes, consider roasting them in the oven for a few minutes. They also heat quickly in a skillet on a medium-high stove eye.
Don’t worry, you can still speed-cook your spuds in the microwave, but you need to take steps to keep them from becoming dangerous if you decide to reheat them later. Potatoes often house Clostridium botulinum, the botulism bacteria. When potatoes are cooked and not immediately stored in the fridge, spores of the bacteria can multiply. Microwaving the potatoes won’t kill the bacteria either, so your second-day potatoes could cause an upset stomach.
How to heat: Move cooked potatoes that won’t be eaten into the fridge as quickly as possible. Also, don’t bake potatoes in an aluminum foil jacket. According to research, the tin catches moisture and accelerates spore growth in the warm, moist environment. For a crispier potato skin—and for the sake of your tummy—bake potatoes without the foil jacket. Then immediately refrigerate them. Don’t let them sit at room temperatures for hours on end. Reheat in the oven.
Bacon, hot dogs, lunch meat, and sausages should be cooked on the stove or in the oven, not in the microwave. That’s because heating these processed meat products leads to the formation of cholesterol oxidation products (COPs). COPs have been linked to coronary heart disease. Research suggests this may also be linked to inflammation, plaque buildup in the arteries, and more health conditions.
How to heat: One study found that grilling also increased the amount of COPs in the meats, so baking in the oven or sautéing may be the safest options.
Heating tomato sauces in the microwave often ends in splatters. The heat and steam produced by the sauce when warmed has a difficult time escaping through the thick sauce or around pieces of ingredients. The steam builds up until it’s powerful enough to burst through—and onto the microwave walls. In some cases, the sauce can even explode when you stir it, which could lead to burns and certainly stained clothes.
How to heat: Heat any sauces in a small pan on the stove. This will allow even heating, and you can stir easily to prevent steam buildup.
Never start an empty microwave. Without food or a container to absorb the microwaves, the beams are bounced back to the magnetron. This could damage the machine and may even start a fire. Double check you’ve put food in the microwave before you press start.