If you've ever seen one of the commercials for defrosting trays like the Miracle Thaw and marveled at how rapidly they are able to melt an ice cube, you may have wondered if they're actually as miraculous as they seem. Is that just trick photography? Or do defrosting trays really work such magic? Let's take a look.
How Defrosting Trays Work
Defrosting trays are made of a material that has a high ability to conduct heat, such as copper or aluminum. Because these metals are good conductors of heat, heat at one part of the metal rapidly moves through it. This causes it to heat up quickly and also cool off quickly.
Compare this with a material like cast iron. Your experience likely tells you that a cast-iron skillet stays hot for a very long time after you're finished cooking with it. That's because cast iron is a very poor conductor of heat. The heat stays trapped in it rather than dissipating into the air around it.
Likewise, a cold copper or aluminum pan will come to room temperature much faster than a cold cast-iron pan.
The Physics of Defrosting Trays
The laws of physics (specifically, thermodynamics) tell us that two objects of different temperatures try to become the same temperature when they come in contact with one another. Place a cold steak on a hot pan and the steak heats up while the pan cools down. That's one reason why it's not a good idea to overcrowd your pan—and why it's so important to let your steak come to room temperature before grilling it.
Which brings us to defrosting trays. Defrosting trays are made of highly conductive metal. Such a tray, when placed on your kitchen counter, will quickly come to the temperature of the air around it, aka room temperature—let's say, 70 F.
Melting Ice on a Defrosting Tray
If, at that point, you were to place an ice cube on that tray, that 70 F surface would meet the 32 F surface of the ice cube, immediately raising the temperature of the surface of the ice cube, causing it to melt.
As it melts, the outer ice vanishes and now the inner ice becomes the surface of the cube. And now that surface is in contact with the surface of the defrosting tray and it too melts. And so on and so on, until there is no more ice left.
And even though the ice is cooling the surface of the tray, the 70 F air continues to warm the tray, and that warmth moves quickly through the tray, including the spot where it ice cube is. So the ice continues to melt quickly. It's quite dramatic, if you've seen one of the commercials.
And yet, your experience also likely tells you that melting ice cubes is not an especially difficult task, certainly not one you would need a special tool for. In any event, melted ice is easily obtainable straight from your faucet.
The real question is, how efficient is a defrosting tray at defrosting other frozen items, like a steak?
And the answer is, not very.
Thawing Food on a Defrosting Tray
The reason is simple. The surface of an ice cube turns to water when its temperature goes up by a few degrees, thus continuously exposing a new surface. But the outer layers of a steak don't melt away. A steak just stays steak. So the defrosting tray will slightly accelerate the warming of the surface of the steak, but not the interior.
That's because unlike copper or aluminum, steak is not a good conductor of heat. When thawing a steak, it's not the air that warms the inner parts of the steak, but rather, the outer parts of the steak itself. And since heat moves slowly through meat, it will take a long time to thaw a frozen steak at room temperature, even on a defrosting tray. The fact is, a defrosting tray will not thaw a frozen steak noticeably faster than your kitchen counter will.
Defrosting Trays and Food Safety
And the problem with taking a long time to thaw a steak is that it becomes a food safety hazard. The bacteria that cause food poisoning reproduce very quickly at room temperature. So by the time your steak has thawed, it will be teeming with dangerous bacteria. Ground meats like hamburger present an even greater danger when thawed this way.
Fortunately, you already possess a perfect tool for defrosting frozen foods. It's called your fridge! And it's easy to use. The night before you're planning to cook your frozen steaks or burgers, simply transfer them from the freezer to the fridge. They'll be thawed by the next day. And assuming your fridge is colder than 40 F, which is the upper limit for preventing the growth of foodborne pathogens, you'll have no worries about food poisoning.