Buzz
I’m a big fan of my microwave. It helps me prepare things like mashed potatoes, roux for gumbo, and even lemon curd. It’s incredibly versatile, and I believe everyone should have one. However, I’m not a huge fan of its defrost function. While I prefer to thaw food using different techniques, it’s still possible to use your microwave to defrost. You just need to pay attention to power levels and timing, and be a bit more hands-on.
How does a microwave’s defrost feature operate?
Before diving into why the microwave’s defrost function isn’t ideal, let’s break down how it works. Every microwave has magnetrons, which are not Transformers but devices that emit electromagnetic (micro) waves. These waves oscillate at incredibly high speeds—about a billion times per second—causing the water molecules in your food to spin in sync with the magnetic field. This fast rotation raises their temperature, thereby heating your food.
As stated by Cook’s Illustrated, unless you're equipped with a high-end, scientific-grade oven, the intensity of microwave radiation cannot be adjusted (either increased or decreased):
Here’s the twist: In most microwaves, the magnetron is designed to emit a fixed wavelength, so the intensity of radiation remains unchanged. However, it can be switched on and off, which is exactly what adjusting the power levels achieves.By lowering the power level, you essentially reduce the duration the magnetron stays on.
Cook’s Illustrated continues to elaborate that microwaves “only penetrate the outer ¼ to 1 inch of food,” and this can lead to rapid superheating in those areas. The on-and-off radiation cycle allows the heat to spread toward the center of the food, slowly warming up that frozen stew without overcooking the outer portion (hopefully). But despite these fluctuations, microwave thawing still presents certain challenges.
Microwaves are not very effective at melting ice.
Ice is water in its solid form, but its crystalline structure makes it harder to melt using microwave radiation. As noted by thenakedscientists, this unique structure prevents the water molecules from rotating as they would in their liquid form.
In ice, water molecules are arranged in a crystal lattice held together by hydrogen bonds. These bonds prevent the molecules from rotating, which reduces their ability to absorb microwave energy. As a result, the ice doesn't warm up effectively.
Eventually, some ice will start to melt—since it's not kept in a freezer—and the water molecules on the surface will begin to rotate. This can cause uneven heating, where the outside becomes cooked while the inside remains frozen, especially when defrosting on high power. This can lead to unsatisfactory and potentially hazardous results, depending on what you're thawing.
The reason for the intermittent breaks in microwave radiation during the defrost cycle is to allow heat from the rotating water molecules to spread to their frozen neighbors, helping to thaw the ice more evenly.
While this method works decently for foods like soups, casseroles, and gravies, it's not ideal for frozen meats. Thinner, smaller cuts might fare better, but attempting to defrost a thick cut, like a two-inch ribeye, in the microwave is a bad idea. Even with the power pauses, the exterior will receive far more radiation than the interior. When you consider the uneven shape of chicken breasts, you’re left with rubbery spots and partially-cooked edges.
The most effective method for defrosting meat is not using the microwave.
The safest and most effective way to defrost frozen meat is by placing it in the refrigerator overnight. While it may be tempting to leave it out at room temperature, this method is unsafe because it puts the food in the 'danger zone'—a temperature range where bacteria thrive. If you're short on time, you can submerge the meat (wrapped) in cold water, changing the water every 30 minutes until it thaws, which usually takes between 30 minutes and an hour per pound.
For thinner cuts of meat, such as steaks, chops, or tenders, you can quickly thaw them using a hot water bath. This method only takes a few minutes, which is too brief for bacteria to develop. (Make sure to cook the meat immediately to prevent it from lingering in the danger zone.) If you're looking to speed things up further, you can use an immersion circulator. This tool also allows you to cook frozen meat by adding roughly an extra half hour, depending on the cut.
If you absolutely must use the microwave, bypass the 'defrost' button and manually adjust the power levels and time. For boneless cuts, such as chicken breasts or tenders, start with 30% power for two minutes, then break the meat apart and flip it. Lower the power to 20% and continue microwaving in 1-minute intervals, flipping and breaking it apart after each interval until it’s thawed. For ground meat, start at 50% power for two minutes, then reduce to 30% power for 1-minute bursts. Be sure to remove thawed pieces and leave the frozen parts behind. It's best not to microwave bone-in cuts or large, thick steaks and chops. Treat your meat with respect and use a water bath or fridge for defrosting instead.
