92 The Science of Lemonade-Low

The Science of Lemonade FOCUS Question How does the balance of chemicals in lemonade affect how it tastes?

柠檬水的科学焦点问题柠檬水中化学物质的平衡是如何影响它的味道的?

Tasty Chemistry Gulp, gulp, gulp... aaah! You just drank an ice-cold glass of lemonade. Alone, lemons are sour enough to make your face pucker. But lemonade is just the right mixture of tangy and sweet. What makes this lemony liquid so yummy? That delicious taste comes from the chemicals in the basic ingredients of fresh lemonade: water, lemons, and sugar. You might drink premixed lemonade from a carton or mix water with a powder or frozen concentrate. Those types of lemonade may taste a little different because of other added ingredients. But the final product is still a combination of chemicals that gives your tongue a treat.

大口，大口，大口…… 啊!你刚喝了一杯冰凉的柠檬水。 单独来说，柠檬酸得足以让你皱起脸来。 但柠檬水是辛辣和甜味的完美结合。 是什么让这种柠檬汁如此美味? 这种美味的味道来自于新鲜柠檬水基本成分中的化学物质:水、柠檬和糖。 你可以喝盒装的混合柠檬水，也可以把水和粉末或冷冻浓缩液混合。 由于添加了其他成分，这些类型的柠檬水尝起来可能会有点不同。 但最终的产品仍然是一种化学物质的组合，让你的舌头享受美味。

That glass of lemonade tasted so good you make another one. Following your recipe, you measure the right amounts of water, lemon juice, and sugar. You then combine the liquids and solids in a glass. You stir a few times and take a drink. Wait! That's not lemonade! The sugar has not dissolved and has mostly settled to the bottom. You have made a heterogeneous (HEH-tur-o-JEE-nee-us) mixture, which means the parts are still separate. Stir until the sugar dissolves and the clear water turns yellow. Now you have stirred up a lemony, sweet solution. All the ingredients mixed together evenly to make a homogeneous (HO-muh-GEE-nee-us) mixture. Your last sip will taste the same as your first. Also, it would be difficult to separate the ingredients. This is lemonade!

那杯柠檬水太好喝了，你又做了一杯。 按照你的食谱，测量适量的水、柠檬汁和糖。 然后将液体和固体混合在一个玻璃杯中。 你搅拌了几次，喝了一杯。 等等!那不是柠檬水!糖还没有溶解，大部分都沉到水底了。 你已经做出了一种异质(heh - turo - jee -nee-us)混合物，这意味着这些部分仍然是分开的。 搅拌至糖溶解，清水变黄。 现在你已经搅拌出了一种柠檬味的甜味溶液。 所有的成分均匀地混合在一起，形成一个均匀的(HO-muh-GEE-nee-us)混合物。 最后一口的味道和第一口是一样的。 而且，很难将成分分开。 这是柠檬水!

What's Happening in the Glass? Your three ingredients form a well-mixed solution because of the attraction between their atoms. Atoms that have negative charges connect, or bond, with atoms that have positive charges. A water molecule has two hydrogen atoms (slight positive charge) and one oxygen atom (slight negative charge). Sugar, or sucrose, also has hydrogen and oxygen atoms with slightly positive and negative charges. When you add sugar to water, the atoms in the two substances are attracted to each other. The natural citric acid from the lemon juice has atoms with positive charges that are attracted to the negative charges in the water molecules. All these bonded atoms form a sweet-tasting solution.

眼镜里发生了什么? 你的三种成分由于原子间的相互吸引形成了一种混合良好的溶液。 带负电荷的原子与带正电荷的原子连接或结合。 一个水分子有两个氢原子(带少量正电荷)和一个氧原子(带少量负电荷)。 糖，或蔗糖，也有带轻微正电荷和负电荷的氢原子和氧原子。 当你把糖加到水里时，这两种物质中的原子就会相互吸引。 柠檬汁中的天然柠檬酸含有带有正电荷的原子，这些原子被水分子中的负电荷所吸引。 所有这些结合在一起的原子形成了一种甜味的溶液。

Sweet over Sour The tangy, sweet taste of lemonade is due to the citric acid and the sucrose at work. In water, sucrose (sugar) begins to break down into two different molecules, glucose and fructose. Citric acid molecules from the lemon juice speed up this process. The newly released fructose is sweeter than sucrose, so now the lemonade tastes sweeter. Sometimes it takes a few tries to get the right balance of sweet and sour when you're making lemonade. Sucrose is a good flavor suppressor. It overpowers other flavors, especially the sourness of citric acid. Sucrose also resists being overpowered by other flavors It is a good idea to follow a recipe closely so you don't make lemonade that's too sweet.

柠檬水浓烈的甜味是由于柠檬酸和蔗糖的作用。 在水中，蔗糖开始分解成两种不同的分子，葡萄糖和果糖。 柠檬汁中的柠檬酸分子加速了这一过程。 新释放的果糖比蔗糖更甜，所以现在柠檬水尝起来更甜了。 制作柠檬水时，有时需要尝试几次才能达到酸甜的平衡。 蔗糖是一种很好的味道抑制剂。 它盖过了其他味道，尤其是柠檬酸的酸味。 严格按照食谱制作柠檬水是个好主意，这样你就不会做出太甜的柠檬水。

Taste, the Tongue, and the Brain Remember that first sip of lemonade? You tasted it with your tongue, but your brain told you what flavor you were sensing. Inside your mouth are about five to ten thousand taste buds that detect chemicals. The more taste buds you have, the more sensitive you are to tastes, especially bitter tastes. Most of your taste buds are located on the bumps, or papillae (puh-PIL-ee), that cover your tongue. Each taste bud has special detectors for five different types of tastes: sweet, sour, salty, bitter, and umami. (Umami is the taste that is found in foods such as meat, tomatoes, and soy sauce.) Fact or Fiction? People once believed that the tongue had specific areas for each taste. But in fact, all parts of the tongue can sense many different tastes.

味觉、舌头和大脑还记得第一口柠檬水吗? 你用舌头尝了尝，但你的大脑告诉你你闻到了什么味道。 在你的口腔中，大约有5到1万个味蕾可以检测化学物质。 你的味蕾越多，你对味道就越敏感，尤其是苦味。 你的大部分味蕾位于覆盖舌头的肿块或乳头上。 每个味蕾都有针对甜、酸、咸、苦和鲜味这五种不同口味的特殊探测器。 (鲜味存在于肉类、番茄和酱油等食物中。)事实还是虚构? 人们曾经认为，舌头有特定的区域来品尝每种味道。 但事实上，舌头的所有部位都能感知许多不同的味道。