Why do frozen turkeys crack when deep frying?

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 in damages, trips to the ER, and even deaths result from attempts to deep-fry a turkey. Most of these accidents happen because people put frozen turkey in boiling oil. If you’re considering deep-frying this year, be sure to deep-fry the turkey before placing it in the pot. Failure to do so could lead to an explosive disaster.

What’s so dangerous about putting even partially frozen turkey in the deep-fryer?

I am a chemist who studies plant, fungal and animal compounds and love food chemistry. The reason frozen turkey explodes, at its core, has to do with differences in density. There is a difference in the densities of oil and water, and there is a difference in the density of water between its solid, liquid, and gas states. When these density differences interact in the right way, you get an explosion.

Understanding Density

Density is how much an object weighs in a specific volume. For example, imagine that you hold 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.

The first important density difference when it comes to frying is that water is denser than oil. This is related to how tightly the molecules of each substance are packed together and how heavy are the atoms that make up each liquid.

Water molecules are small and packed tightly together. Oil molecules are very large and are comparatively not packed together. Additionally, water is made up of oxygen and hydrogen atoms, while oils are primarily carbon and hydrogen. Oxygen is heavier than carbon. This means that, for example, a cup of water contains more atoms than a cup of oil, and the atoms of those individuals are heavier. That’s why oil floats on top of water. It is less dense.

While different materials have different densities, liquids, solids and gases of the same material can also have different densities. Every time you place an ice cube in a glass of water you see this: ice floats to the top because it is less dense than water.

When water absorbs heat, it turns into its gas phase, steam. A volume equal to the number of molecules of liquid water occupies 1,700 times the volume of steam. You see this effect when you boil water in a tea kettle. The force of the expanding gas pushes the steam out of the kettle through the whistle, producing a squeaky sound.

frozen turkey filled with water

Frozen turkey — or any type of frozen meat, for that matter — takes a lot of ice. Raw meat can contain anywhere from 56% to 73% water. If you’ve ever thawed a piece of frozen meat, you’ve probably noticed all the liquid that comes out.

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

This quick transition is not a problem when it occurs on an oily surface. The steam escapes harmlessly into the air.

However, when you submerge a turkey in oil, the ice inside the turkey absorbs the heat and melts, creating liquid water. Here is where density comes into play.

This liquid water is more dense than oil, so it tends to fall to the bottom of the pot. Water molecules continue to absorb heat and energy and eventually they change phase and become vapor. The water molecules then rapidly disperse away from each other and the volume expands 1,700 times. This expansion causes the density of water to drop to a fraction of a percent of the density of oil, so the gas tends to rise to the surface quickly.

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Combine the rapid change in density with the expansion of volume and you get an explosion. The steam expands and rises, pushing the boiling oil out of the pot. If that weren’t dangerous enough, as the displaced oil comes into contact with the burner or flame, it could catch fire. Once a few drops of oil are ignited, the flames will quickly ignite the surrounding oil molecules, resulting in fast-moving and often catastrophic fires.

Thousands of such accidents happen every year. So, should you decide to deep-fry the turkey for this year’s Thanksgiving, make sure to thaw it thoroughly and pat dry. And the next time you pour a little liquid into a pan filled with oil and fill it with oil on the stove, you’ll know the science.