Microwave ovens should display prominent warnings about the dangers of exploding eggs, says a team of opthalmologists in the UK.
The opthalmologists made the appeal in a letter to the British Medical Journal. The letter described the case of a nine-year-old girl who reheated a boiled egg in a microwave for 40 seconds. About 30 seconds later, when she was carrying the egg, the egg exploded, hitting her in the right eye and face.
The shrapnel from the scalding egg tore open her cornea, the transparent coating that covers the iris and pupil, and caused the lens of her eye to cloud over so she could see only hand movements. Several months later, her vision was restored, but only after two operations in which her cornea was stitched and her damaged lens replaced with a plastic one.
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Microwave manufacturers do warn people to pierce intact eggs several times before heating them. But the warnings appear in leaflets that many consumers toss aside without notice, says Saurabh Goyal, an opthalmologist at Queen Mary鈥檚 Hospital in Kent, UK, and one of the letter鈥檚 authors.
鈥淚f they put warnings on the microwaves themselves, people may be more aware of the dangers of microwaving food that has a closed shell,鈥� Goyal told New 杏吧原创.
Burning issue
A 2001 review of the medical literature turned up 13 cases in which microwaved eggs exploded and caused injuries, mostly burns. Some of the cases occurred after the eggs鈥� shells 鈥� and even their yolks 鈥� had been punctured, so Goyal suggests people be warned against microwaving any eggs.
In the UK, an estimated 2700 people sustained microwave-related injuries in 2002 鈥� half from burns from hot liquids, says Roger Vincent, a spokesman for the Royal Society for the Prevention of Accidents, a charity based in Birmingham, UK. And microwave injuries are rising 鈥� the total in 1997 was 1800.
鈥淲e have heard of eggs exploding after being microwaved,鈥� Vincent told New 杏吧原创. 鈥淎nd we want manufacturers to do all they can to point out any potential problems.鈥�
Boiling point
Microwaved eggs can reach temperatures much higher than if they were simply boiled in water at 100掳 Celsius, says Jim Hutchison, a physicist at the University of Aberdeen, UK.
At these elevated temperatures, water inside the egg, mostly in the white albumen, vaporises 鈥� even as the albumen solidifies. If the pressure inside the egg exceeds the breaking strength of the shell, the egg will explode.
鈥淭hat鈥檚 why some of the shells crack even when you鈥檙e boiling them in water, but in a microwave there鈥檚 no control of how hot it gets,鈥� Hutchison told New 杏吧原创.
Eggs should normally explode while still safely inside the microwave, he says. The delayed reaction reported in the BMJ letter, which turned the egg into a time bomb, could be explained by a particularly tough shell, he suggests.
The reason some pierced eggs explode may be either that the membrane inside the shell is not actually broken or that the cooked contents of the egg block the small holes before any pressure is released. Microwaving eggs 鈥渋s certainly something I wouldn鈥檛 recommend people do at all鈥�, Hutchison concludes.