Every fall, millions of dollars in damages, trips to the emergency room and even deaths result from attempts to fry turkeys. The vast majority of these accidents happen because people put frozen turkeys in boiling oil. If you’re thinking of deep-frying this year, don’t forget to thaw and dry your turkey before placing it in the pot. Failure to do so could result in an explosive disaster.
What’s dangerous about putting even a partially frozen turkey in a deep fryer?
I am a chemist who studies plant, fungal and animal compounds and I love food chemistry. The reason frozen turkeys explode, in essence, 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 gaseous states. When these differences in density interact in the right way, an explosion occurs.
Density is the amount of weight of an object given a given volume. For example, imagine you are holding an ice cube in one hand and a marshmallow in the other. While they are about 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 has to do with how tightly together the molecules of each substance are and how heavy the atoms that make up each liquid are.
Water molecules are small and tightly packed. The oil molecules are much larger and are not grouped together when compared. In addition, water is composed of oxygen and hydrogen atoms, while oils are composed mostly of carbon and hydrogen. Oxygen is heavier than carbon. This means, for example, that 1 cup of water contains more atoms than 1 cup of oil, and that those individual atoms are heavier. This is why oil floats on top of water. It is less dense.
While different substances have different densities, liquids, solids, and gases from one substance can also have different densities. You notice this every time you put an ice cube in a glass of water: Ice floats to the top because it’s less dense than water.
When water absorbs heat, it turns into the gas phase, vapor. Vapor occupies 1,700 times the volume of the same number of molecules as liquid water. You notice this effect when boiling water in a teakettle. The force of the expanding gas forces the steam out of the boiler through the whistle, causing a squealing noise.
Frozen turkeys are filled with water
Deep frying a turkey can be safe as long as the turkey is thawed and dried. Photo credit: Chad Robertson Media / Shutterstock.com
Frozen turkeys — or any type of frozen meat, contain a lot of ice. Raw meat can contain anywhere from 56% to 73% water. If you’ve ever thawed a frozen piece of meat, you’ve probably seen all the liquid come out.
For deep frying, cooking oil is heated to about 350°F (175°C). This is hotter than the boiling point of water, which is 212 F (100 C). So when the ice in a frozen turkey comes into contact with the hot oil, the surface ice quickly turns to steam.
This rapid transition is not a problem when it occurs on the surface of the oil itself. The vapor escapes harmlessly into the air.
However, when the turkey is submerged in oil, the ice inside the turkey absorbs the heat and melts, creating liquid water. This is where density comes into play.
This liquid water is denser than oil, so it falls to the bottom of the container. The water molecules continue to absorb heat and energy and eventually change phases and become vapor. Then the water molecules quickly spread apart from each other and the volume expands by 1,700 times. This expansion causes the density of water to drop to a fraction of a percentage of the density of oil, so the gas wants to rise quickly to the surface.
Combine a quick change in intensity with an increase in volume and you’ve got a blast. The steam expands and rises, spewing boiling oil into the pot. If this isn’t serious enough, the displaced oil comes in contact with the burner or flame, it can ignite. Once a few drops of oil are on fire, nearby oil particles will quickly catch fire, resulting in a fast-moving and often catastrophic fire.
Every year, thousands of accidents like this happen. So if you decide to fry your turkey this Thanksgiving, make sure it’s completely thawed and dried. And the next time you add a little liquid to an oiled pan and end up with oil all over the stove, you’ll know why.
Kristen Nolen, Assistant Professor of Chemistry, University of Richmond
This article is republished from The Conversation under a Creative Commons license. Read the original article.