Why do frozen turkeys explode when deep-fried?

Deep-frying a turkey is a great way to get a delicious, moist meal for Thanksgiving. But this method of cooking can be a very dangerous undertaking.

Every fall, millions of dollars of damage, trips to the ER and even deaths result from attempts to deep-fry turkeys. The vast majority of these accidents happen because people put frozen turkeys into boiling oil. If you are considering deep-frying this year, do not forget to thaw and dry your turkey before placing it in the pot. Failure to do so may lead to an explosive disaster.

What is so dangerous about putting even a partially frozen turkey in a deep-fryer?

The reason frozen turkeys explode, at its core, has to do with differences in density. There is a difference in density between oil and water and differences in the density of water between its solid, liquid and gas states. When these density differences interact in just the right way, you get an explosion.

Understanding density

Density is how much an object weighs given a specific volume. For example, imagine you held an ice cube in one hand and a marshmallow in the other. While they are roughly the same size, the ice cube is heavier: It is more dense.

Water is denser than oil. This has to do with how tightly the molecules of each substance pack together and how heavy the atoms are that make up each liquid. This means that, for example, one cup of water has more atoms than one cup of oil, and those individuals atoms are heavier. This is why oil floats on top of water: It is less dense.

While different materials have different densities, liquids, solids and gases of a single material can have different densities as well. You observe this every time you place an ice cube in a glass of water: The ice floats to the top because it is less dense than water.

When water absorbs heat, it changes to its gas phase, steam. Steam occupies 1,700 times the volume as the same number of liquid water molecules. When water boils in a tea kettle, the force of expanding gas pushes steam out of the kettle through the whistle, causing the squealing noise.

Frozen turkeys are filled with water

Frozen turkeys – or any kind of frozen meats, for that matter – contain a lot of ice. Raw meat can be anywhere from 56% to 73% water. When a frozen piece of meat thaws, a lot of liquid comes out.

For deep-frying, cooking oil is heated to about 350 degrees Fahrenheit (175 C). This is much hotter than the boiling point of water, which is 212 F (100 C). So when the ice in a frozen turkey comes in contact with the hot oil, the surface ice quickly turns to steam.

This quick transition is not a problem when it happens at the very surface of the oil. The steam escapes harmlessly into the air.

But when a turkey gets dropped into the oil, the ice inside the turkey absorbs the heat and melts, forming liquid water. Here is where the density comes into play.

This liquid water is denser than the oil, so the water falls to the bottom of the pot and eventually turns into steam, expanding 1,700 times. This expansion causes the density of the water to drop to a fraction of a percent of the density of the oil, so the gas rises quickly to the surface. The steam then blows the boiling oil out of the pot.

As the displaced oil comes into contact with a burner or flame, it catches fire, resulting in a fast-moving and often catastrophic fire.

Every year, thousands of accidents like this happen. So, should you decide to deep-fry a turkey for this year’s Thanksgiving, be sure to thoroughly thaw it and pat it dry. And next time you add a bit of liquid to an oil-filled pan and end up with oil all over the stove, you’ll know the science of why.

This article by Kristine Nolin of the University of Richmond is published from The Conversation through a Creative Commons license.

Staff is home to The NorthSider and The SouthSider weekly community newspapers. The SouthSider publishes 25,000 copies every Tuesday. The NorthSider publishes 25,000 copies every Thursday. They are distributed at over 600 locations across St. Louis.

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