artee 2008-1-20 23:46
为什么切洋葱会流泪
[size=1][size=12pt][size=1][size=12pt][size=1][size=12pt]洋葱营养价值高，是高血压、高血脂病人的绝佳保健食品。可是切洋葱的时候，总是会被洋葱的味道辣得流泪。想知道这是为什么吗？请看下面的文章。[/size][/size][/size][/size][/size][/size]
[size=1][size=12pt][size=1][size=12pt][size=1][size=12pt][img=120,126]http://www.chinadaily.com.cn/language_tips/easyEnglish/attachement/jpg/site1/20080102/0013729c002508e596230d.jpg[/img]It is not the strong odor of the onion that makes us cry, but the gas that the onion releases when we cut this member of the lily family.[/size][/size][/size][/size][/size][/size]
[size=1][size=12pt][size=1][size=12pt]The onion itself contains oil, which contains [b][color=olive]sulfur[/color][/b], an [b][color=olive]irritant[/color][/b] to both our noses and to our eyes. Cutting an onion arouses a gas contained within the onion, propanethiol S-oxide, which then couples with the [b][color=olive]enzymes[/color][/b] in the onion to emit a passive sulfur compound. When this upwardly mobile gas encounters the water produced by the [b][color=olive]tear-ducts[/color][/b] in our eyelids, it produces sulfuric acid.[/size][/size][/size][/size]
[size=1][size=12pt][size=1][size=12pt][img=150,187]http://www.chinadaily.com.cn/language_tips/easyEnglish/attachement/jpg/site1/20080102/0013729c002508e596230e.jpg[/img]In response to the caustic acid, our eyes automatically blink, and produce tears which irrigate the eye, and which flush out the sulfuric acid.[/size][/size][/size][/size]
[size=1][size=12pt][size=1][size=12pt]Another reflex to rid the eyes of a foreign substance, that of rubbing our eyes with our hands, often [b][color=olive]exacerbates[/color][/b] the situation, because our hands are coated with the caustic, sulfuric acid producing oil from cutting the onion, which we then rub directly into our eyes.[/size][/size][/size][/size]
[size=1][size=12pt][size=1][size=12pt]Much to our chagrin, the only remedy for ridding the onion of its pungent, irritating oil is to boil it, not to slice it or [b][color=olive]dice[/color][/b] it.[/size][/size][/size][/size]
[size=1][size=12pt][size=1][size=12pt]sulfur: 硫磺[/size][/size][/size][/size]
[size=1][size=12pt][size=1][size=12pt]irritant: 刺激[/size][/size][/size][/size]
[size=1][size=12pt][size=1][size=12pt]enzyme: 酶[/size][/size][/size][/size]
[size=1][size=12pt][size=1][size=12pt]tear-duct: 泪管[/size][/size][/size][/size]
[size=1][size=12pt][size=1][size=12pt]exacerbate: 加剧，恶化[/size][/size][/size][/size]
[size=1][size=12pt][size=1][size=12pt]dice: 切成丁[/size][/size][/size][/size]