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  • Scientific American Instant Egghead

  • Start chopping a pungent onion

  • and before too long you're bound to tear up.

  • How exactly does this bulbous veggie have the power to make us cry?

  • The second you slice into an onion you change its chemistry.

  • Cutting an onion ruptures its cell walls.

  • You can think of these walls as sturdy balloons

  • that hold in a cells contents.

  • When a knife breaks through, [pop]

  • swarms of molecules and enzymes escape.

  • Some of those enzymes break down sulfur compounds present in the onion

  • generating sulfenic acids in the process.

  • Other chemical reactions convert sulfenic acids

  • into a volatile and irritating gas called onion lachrymatory factor.

  • When this gas wafts into your eyes,

  • certain neurons instruct your tear ducts to flush out this potentially harmful substance.

  • Fortunately, there are a few tricks you can use to keep the waterworks to a minimum.

  • Storing the onion in the fridge or freezer for at least 30 minutes before chopping,

  • slows down its enzymes which should help prevent tears.

  • Briefly boiling an onion should have the same effect.

  • High heat can deactivate enzymes.

  • Another strategy is cutting the onion under running water

  • to prevent the gas from reaching your eyes.

  • But the easiest solution is probably a pair of ski goggles or sunglasses.

  • Hmm

  • [chop, chop]

  • Umm, if goggles or glasses don't work out so well, don't worry.

  • Scientists are trying to tackle the problem too.

  • Researchers in Japan and New Zealand have collaborated to create a tear free onion.

  • They silenced one of the genes that makes onion lachrymatory factor, the volatile gas that irritates your eyes.

  • But don't look for it on the shelf, this genetically modified product is not currently on the market.

  • Other researchers used traditional plant breeding to create the "Ever Mild", a yellow onion with really low levels of the volatile gas.

  • You can find it in some grocery stores.

  • But until these products are more widely available, we'll probably have to stick with Kleenex and sunglasses.

  • For Scientific American's Instant Egghead, I'm Ferris Jabr.

  • [music]


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B2 US onion gas volatile instant tear goggles

Why Do Onions Make Us Cry? - Instant Egghead #62

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    羅紹桀 posted on 2015/09/12
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