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TED-Ed 068・・The science of spice （辛さの科学）

辛さは味覚ではなく熱の痛覚。 適度ならよいが取り過ぎは火傷のようなもの。

難　04分・・195wpm　　2014/05/02 新出
　

★下記英文はｸﾞｰｸﾞﾙのマウスオーバー辞書が使えます｡ 　　　　　　

Why does your mouth feel like it's on fire when you eat a spicy pepper? And how do you soothe（和らげる） the burn? Why does wasabi make your eyes water? And how spicy is the spiciest spice? Let's back up a bit.

First, what is spiciness? Even though we often say that something tastes spicy, it's not actually a taste, like sweet or salty or sour. Instead, what's really happening is that certain compounds in spicy foods activate the type of sensory neurons called polymodal nociceptors（ﾎﾟﾘﾓﾀﾞｰﾙ傷害受容器＝強い熱に反応）.

You have these all over your body, including your mouth and nose, and they're the same receptors that are activated by extreme heat. So, when you eat a chili pepper, your mouth feels like it's burning because your brain actually thinks it's burning.

The opposite happens when you eat something with menthol in it. The cool, minty compound is activating your cold receptors. When these heat-sensitive receptors are activated, your body thinks it's in contact with a dangerous heat source and reacts accordingly.

This is why you start to sweat, and your heart starts beating faster. The peppers have elicited the same fight-or-flight response（闘争・逃走反応） with which your body reacts to most threats. But you may have noticed that not all spicy foods are spicy in the same way.

And the difference lies in the types of compounds involved. The capsaicin（ｶﾌﾟｻｲｼﾝ） and piperine（ﾋﾟﾍﾟﾘﾝ）, found in black pepper and chili peppers, are made up of larger, heavier molecules called alkylamides（ｱﾙｷﾙｱﾐﾄﾞ）, and those mostly stay in your mouth. Mustard, horseradish, and wasabi are made up of smaller molecules, called isothiocyanates（ｲｿﾁｵｼｱﾈｰﾄ）, that easily float up into your sinuses（鼻腔）.

This is why chili peppers burn your mouth, and wasabi burns your nose. The standard measure of a food's spiciness is its rating on the Scoville scale, which measures how much its capsaicin content can be diluted before the heat is no longer detectable to humans.
　　　（Scoville scale＝ｽｺｳﾞｨﾙ値。 唐辛子の成分 ｶﾌﾟｻｲｼﾝ の割合）

A sweet bell pepper（ﾊﾟﾌﾟﾘｶ）gets 0 Scoville heat units, while Tabasco sauce clocks in between 1,200-2,400 units. The race to create the hottest pepper is a constant battle, but two peppers generally come out on top: The Trinidad Moruga Scorpion（ﾄﾘﾆﾀﾞｰﾄﾞ･ﾓﾙｶﾞ・ｽｺｰﾋﾟｵﾝ）and the Carolina Reaper（ｷｬﾛﾗｲﾅ・ﾘｰﾊﾟｰ）.

These peppers measure between 1.5 and 2 million Scoville heat units, which is about half the units found inpepper spray（催涙ガス）. So, why would anyone want to eat something that causes such high levels of pain? Nobody really knows when or why humans started eating hot peppers.

Archaeologists have found spices like mustard along with human artifacts dating as far back as 23,000 years ago. But they don't know whether the spices were used for food or medication or just decoration. More recently, a 6,000 year old crockpot, lined with charred fish and meat, also contained mustard.
　　　（crockpot＝煮込み用の電気鍋、ここでは単なる鍋の意味）

One theory says that humans starting adding spices to food to kill off bacteria. And some studies show that spice developed mostly in warmer climates where microbes also happen to be more prevalent. But why we continue to subject ourselves to spicy food today is still a bit of a mystery.

For some people, eating spicy food is like riding rollercoasters; they enjoy the ensuing thrill, even if the immediate sensation is unpleasant. Some studies have even shown that those who like to eat hot stuff are more likely to enjoy other adrenaline-rich activities, like gambling.
　　　（ジェットコースターは和製英語、英語ではrollercoaster）

The taste for spicy food may even be genetic（遺伝子学的）. And if you're thinking about training a bit, to up your tolerance for spice, know this: According to some studies, the pain doesn't get any better. You just get tougher.
　　　（痛みは少しも変わらず、ただ我慢強くなるだけ）

In fact, researchers have found that people who like to eat spicy foods don't rate the burn any less painful than those who don't. They just seem to like the pain more. So, torment your heat receptors all you want, but remember, when it comes to spicy food, you're going to get burned.
　　　（ようするに火傷はしている）