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為什么食物吃起來有甜味
Whether it’s ice cream, chocolate, candy,cookies or cake, we like our sweet stuff.
無論是冰激凌，巧克力，糖果，餅干還是蛋糕，我們都喜歡甜食。
But have you ever thought about why you have that sweet tooth?
但是你是否想過，你為什么喜歡甜食？
Turns out, it’s all about evolution.Let’s hear more from this gentleman...
事實表明，這都是進化的結果。讓我們聽這位紳士解釋一下……
“The reason is that in nature, foods that are sweet are incredibly rare,but they’re a great source of energy. Sucrose is a carbohydrate. As is glucose,fructose, etc. Carbohydrates are molecules that contain an awful lot of energy. So mammals, whenever they found a source of carbohydrates, ate as much of it as they could.”
“原因就是，在自然界中，有甜味的食物非常罕見，但是它們是大量能量的來源。蔗糖是一種碳水化合物。就像葡萄糖，果糖等等。碳水化合物是含有大量能量的分子。所以，哺乳動物任何時候找到碳水化合物資源，都會盡可能多吃一些。”
Now we’re not running away from sabretooth tigers and walking miles for food any more.
現在，我們不再需要躲避劍齒虎，行走數英里來尋找食物了。
But what makes these foods taste,you know, sweet?
但是，你知道是什么讓這些食物吃起來有甜味嗎？
To be sweet, a molecule has to have three very specific chemical features that form a triangle of just the right size.
要吃起來有甜味，分子必須有三種特定的化學特征，形成特定大小的三角形。
Here is how sucrose, or table sugar,fits into the delightfully name 'sweetness triangle.'
這就是蔗糖有著非常可愛的名字“甜蜜三角形”的原因。
Scientists have different ways of describing this interaction, but one way is like a hand in a glove.
科學家有著不同的方式來描述這種互動，但是其中一種就像是戴著手套的手。
If the molecule in your food or drink and the receptor on your tongue fit together, your brain gets an electrical impulse that says“sweeeeet.”
如果食物或飲料中的分子和舌頭上的感受器能夠匹配，你的大腦就會收到電沖信號告訴你“很甜”。
“But what about artificial sweeteners?“our diet-sipping soda viewers ask.
“但是如果是人造甜味劑呢？”我們的觀眾問。
The granddaddy is saccharin, which was widely used during world war one when sugar was strictly rationed.
人造甜味劑的鼻祖是糖精，在第一次世界大戰期間得到廣泛使用，當時糖是經過嚴格分配的。
It’s still around today as “sweet –n– low”.And it’s in tab. Remember tab?
今天，這種產品仍然存在，就好像“sweet –n– low”一樣。還有tab，你還記得嗎？
By the年代， 80s artificial sweeteners went big time with aspartame, you’ve seen it marketed as “nutrasweet” or “equal”, and it is almost certainly in your favorite diet soda.
截止到80年代，人造甜味劑迎來了代糖的鼎盛時期，你看到他們的市場推廣標榜為“阿斯巴甜”或“等同于糖”，你最喜歡的蘇打水中幾乎肯定有這種甜味劑。
But here’s the funny thing. Aspartame doesn’t look anything like table sugar, or sucrose.
但是有趣的是，阿斯巴甜看上去完全不像蔗糖。
“Now, aspartame, as a molecule,isn’t even close to a sugar.It’s in fact a tiny little protein.It’s the addition of aspartic acid and phenylalanine, known as amino acids,this means that aspartame is chemically more similar to meat than it is to sugar.”
“從分子結構上講，阿斯巴甜和糖完全不接近。實際上阿斯巴甜是一種微小的蛋白質。它是天門冬氨酸和苯基丙氨酸的結合，這些都是氨基酸。這意味著阿斯巴甜在化學結構上與肉更接近。”
So artificial sweeteners taste sweet because they fit into the sweetness triangle.
所以，人造甜味劑吃上去是甜的是因為它們剛好構成甜蜜三角形。
But only part of the aspartame molecule fits. Chemists have since created or discovered other molecules like sucralose, and stevia,both of which are sweeter than aspartame, and hundreds of times sweeter than table sugar.
但是只有部分阿斯巴甜分子能夠符合。化學家創造或發現了其他分子，比如果糖和甜菊，兩者都比阿斯巴甜更甜，比蔗糖甜數百倍。
So that’s why things taste sweet.
以上就是食物吃起來甜的原因。
