时差N小时 果胶是什么（在线收听）

It's pretty easy to guess what most of your food is made of. The meat in your hamburger probably came from a cow, the bun was made from grain, the ketchup from tomatoes, and so on. There is one kind of food, however, that might have you guessing animal, vegetable or mineral for the whole meal. But no more, since we'll learn about Jello on today's Moment of Science.

要猜出大多数食物是由什么做成的十分简单。汉堡里的肉可能来自于牛，小圆面包可能来自谷物，番茄酱由西红柿做成，等等。然而有一种食物就不容易猜了，到底它是来自于植物、动物还是矿物质呢？没关系，学了今日科学时刻关于果胶的知识后，你就不会再感到迷惑了。

Jello is a trademark name for gelatin, a food that people have enjoyed for generations. To answer the question animal, vegetable, or mineral: gelatin is an animal product. It is prepared by soaking the bones, skin, or connective tissue from pigs or cows in a bath of mild hydrochloric acid solution. After this, the animal products are heated in distilled water for many hours, and finally boiled. The fluid that collects from this process is drawn off.

果胶是明胶的商业用名，是一种几代人都享用过的食物。从植物、动物或者矿物质中选择一个来回答这个问题的话，那就是动物。果胶的制作方法是，用轻度的盐酸溶液浸泡牛或者猪的骨头，皮肉或者结缔组织；之后用蒸馏水加热几个小时直至沸腾；在这个过程中收集流出来的液体。

What's left is dried, and ground into a fine, pale yellow powder. This is unflavored gelatin, the basis of all gelatin salads, desserts, and drinks. Gelatin is valuable as a food because it is pure protein and it is easy to digest. A gelatin made from vegetable protein, called agar-agar, is made for vegetarians. When powdered gelatin is stirred into hot water and then chilled, it forms the jiggly, gelled product that we are most familiar with. This gelled product is not strictly a solid or a liquid.

把最后剩下的部分晾干，磨成细小，微黄的粉末。这粉末就是无味的明胶，所有明胶色拉，甜点和饮料的原材料。明胶与天然食物的营养价值相同，因为它是由纯蛋白质组成，并且很好消化。用植物做成的明胶叫做琼脂。琼脂是为素食主义者准备的。当把粉末状明胶混合开水搅拌，然后冷却，就会形成我们非常熟悉的不稳定的、稠化的食品。严格来讲，这种食物既不是固体也不是液体。

Technically it's a colloid: a liquid suspended in a solid framework. As the hot mixture cools off, the long strands of animal protein lock together into a solid framework, trapping tiny droplets of liquid water in the process. It's these droplets of water, trapped in a mesh of animal protein, that hold all the coloring and flavoring in your favorite gelatin dessert.

学术上来说它是胶体：一种液体悬浮在另一种固体中。当热的混合物冷却后，长长的动物蛋白链就会凝聚成一块固体，并在凝聚过程中吸附微小的液态水滴。正是这些水滴锁住了所有的颜色和味道，所以你才能吃上色香味俱全的果胶甜点。