Why You Should Think Twice Before Putting Fried Food In The Microwave

From tasty mug cakes to hot, buttery popcorn, there's a lot that a microwave can do. While you can technically use the appliance to heat up whatever food you want, there are some foods you'll want to keep far away from it — and fried food is at the top of the list. That's right: Those leftover fries or chicken tenders should be heated up elsewhere for the best next-day taste and texture. Kantha Shelke, PhD, the founder and principal of food science and research firm Corvus Blue LLC, and senior lecturer on food safety regulations for Johns Hopkins University, explains exactly why this is the case, and how you should heat up fried food instead for the best results.

Dr. Shelke warns against microwaving fried food because it often ends up leaving the food soggy and unappetizing. "Microwaves heat water, not air," she says. Instead of using hot air to cook food from the outside, microwaves penetrate the food directly, exciting water molecules and generating heat from within the food. Additionally, because the inside of a microwave stays at room temperature, it prevents the moisture from evaporating. Instead, the steam condenses and accumulates near the food's surface.

While you may pop your previously crispy, leftover chicken tenders into the microwave without a second thought, they often come out soggy, slimy, or even rancid-tasting. "Crisping requires dehydrating i.e., removing water from the surface, and microwaves do the opposite," Dr. Shelke explains. Frying food in oil between 350-375 degrees Fahrenheit immediately evaporates surface water, creating that crisp texture, according to Dr. Shelke. Microwaves, however, excite internal water molecules, generating heat from within. This creates a rapid internal evaporation and pushes water vapor outward. "As a result, a lot more moisture reaches the surface in microwaved foods than in conventionally fried foods," she explains, eliminating that unbeatable crunch from the food's surface.

Additionally, microwave design also affects crisping. "The cool and unventilated cavities of microwaves favor condensation, not evaporation," Dr. Shelke says. Instead of escaping, steam condenses back onto the surface of your food. "The migrating moisture mixes with the oil of the coating at the outer food surface to produce a greasy, limp surface rather than a crisp one," she explains.

Beyond sogginess, microwaving can cause a rancid flavor because cooking oil reacts differently from water. While water boils at 212 degrees Fahrenheit, oils reach much higher temperatures. "Oils are viscous and conduct heat poorly, so microwaving creates localized hotspots with the oils reaching as high as 355-390 degrees Fahrenheit, while the rest of the food stays cool," Dr. Shelke says. This extreme heat causes the oil to break down fast, releasing volatile chemical compounds that produce a stale flavor. When mixed with a sad, limp french fry, this is a true recipe for disaster.

To avoid soggy and bad-tasting fried food and truly get the most out of your leftovers, Dr. Shelke recommends doing the opposite of what a microwave does. "Strip the surface moisture instead of adding to it," she recommends. There are three kitchen appliances that can aid in this process. Instead of a microwave, try reheating fried food with an oven, an air fryer, or a toaster oven. It might seem like more of a hassle, but it really is worth it — and according to Dr. Shelke, just three to five minutes at around 375-400 degrees Fahrenheit should do just the trick. 

Instead of allowing moisture to condense back onto the surface of your potatoes, chicken, or fish, these appliances will surround the food with dry, hot, circulating air. They will aid in restoring your food's crispness by drying out its surface and removing any surface moisture. Additionally, they'll help you avoid stale-tasting food and dried-out textures, leaving you with the crispiest, most delicious-tasting fried food. It'll be so good, you'd never even know it was reheated.