Your breakfast plate might be more dangerous than you thought. A hard-boiled egg that鈥檚 reheated in the microwave could explode when you bite into it or prick it with your fork, and a new study shows that this may happen up to a third of the time.
, a consultant at Charles M. Salter Associates, was hired as an expert witness for a court case after a restaurant patron allegedly burned his face and suffered hearing damage when a hard-boiled egg exploded in his mouth.
The case was settled out of court, but not fast enough to prevent Nash and his colleague Lauren von Blohn from reheating almost 100 boiled eggs in a microwave to figure out how they explode and whether enough noise is generated to harm a diner鈥檚 ears. They presented their results this week at a meeting of the Acoustical Society of America in New Orleans.
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The eggs were microwaved in a water bath, both because it slows down the heating process and because that鈥檚 how the restaurant in the court case heated theirs. Some of the eggs ruptured or exploded in the microwave over the course of the 3 minutes of heating time.
Detonating eggs
For the eggs that survived heating, Nash and von Blohn removed them from the microwave, placed them on the ground, and pricked them with a meat thermometer. 28 of the eggs exploded. 鈥淚t takes a lot of trials to get an egg to really detonate,鈥� says Nash. 鈥淚t鈥檚 like playing Russian roulette with an egg 鈥� egg roulette.鈥�
Microwaved objects or foods exploding is not a new phenomenon 鈥� many microwaves actually have warnings not to use them to heat items like eggs or potatoes. Even plain water can explode if it gets superheated to temperatures higher than its boiling point in a microwave.
鈥淎 big hospital outpatient department typically reports scalding injuries from such incidents fairly regularly 鈥� say several times per year,鈥� says at the University of New South Wales in Sydney.
Potatoes and other foods with a peel can explode when microwaved because of steam pressure building up inside the skin. But the boiled eggs Nash used had the shell removed, so he suspects another mechanism. He and von Blohn theorise that tiny pockets of water within the egg鈥檚 yolk become superheated, and then start spontaneously boiling in an explosive release of steam when the pockets are punctured by a fork 鈥� or your teeth.
Louder than a chainsaw
In addition to a rush of heat, they found that these 鈥渆ggsplosions鈥� produce a sound that when measured from 30 centimetres away can be as loud as 133 decibels. That鈥檚 louder than a chainsaw being operated 1 metre away.
Nash says that one exposure to this level of noise would be unlikely to damage your hearing, but the effects may be different if you bite into the egg and it explodes in your mouth. 鈥淓ven a small explosion in the mouth or near the ear might plausibly damage hearing,鈥� says Wolfe.
The heat of the explosion could certainly hurt your face, too. 鈥淒on鈥檛 put any eggs in the microwave,鈥� Nash says. 鈥淭hey鈥檙e to be respected, those machines.鈥�
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