Why Does Bread Rise? The Science in Your Kitchen

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1. 01Why Does Bread Rise?

   Good morning. I'm a chemistry teacher, and on weekends, I bake bread with my children. They always ask me, "Why does the dough get bigger?" Today, I'll explain the science, step by step.

   早上好。我是一名化学老师，周末会和孩子们一起烤面包。他们总是问我：“为什么面团会变大呢？”今天，我就一步一步地讲讲其中的科学原理。

2. 02Four Simple Ingredients

   Basic bread needs only four ingredients: flour, water, salt, and yeast. The star of the story is yeast, which is a tiny living thing. It's actually a type of fungus, made of just one cell.

   最基本的面包只需要四种原料：面粉、水、盐和酵母。这个故事的主角是酵母，它是一种微小的生物。其实它是一种真菌，只由一个细胞组成。

   Source: Institute of Food Science & Technology (IFST), Love Food Love Science: "Raising agents: biological (fermentation)"

3. 03Stage 1: Yeast Makes Gas

   In the first stage, yeast feeds on sugars in the dough. As it feeds, it produces carbon dioxide gas and a little alcohol. This process is called fermentation.

   在第一个阶段，酵母以面团里的糖为食。它在进食的同时，会产生二氧化碳气体和少量酒精。这个过程叫作发酵。

   Source: Institute of Food Science & Technology (IFST), Love Food Love Science: "Raising agents: biological (fermentation)"

4. 04Stage 2: Gluten Traps the Gas

   But gas alone isn't enough. It needs to be trapped. When flour is mixed with water, two proteins in wheat form gluten. Kneading makes the gluten stretchy, like a net of tiny balloons that holds the gas.

   但光有气体还不够，还得把它留住。面粉和水混合后，小麦里的两种蛋白质会形成面筋。揉面会让面筋变得有弹性，就像一张由无数小气球组成的网，把气体留住。

   Source: Exploratorium, "Science of Bread: Bread Science 101"

5. 05Stage 3: The Oven

   In the oven, the heat makes the gas expand, so the bread rises even more. The alcohol evaporates, and the yeast is killed by the heat. That's why baked bread doesn't keep growing.

   在烤箱里，热量会让气体膨胀，所以面包会长得更大。酒精会蒸发，酵母也会被高温杀死。所以烤好的面包不会继续变大。

   Source: Institute of Food Science & Technology (IFST), Love Food Love Science: "Raising agents: biological (fermentation)"

6. 06Why Bread Sometimes Fails

   This also explains why my first loaves were flat. If the water is too hot, it can kill the yeast before it starts. If you don't knead enough, the gas escapes. And if you're impatient, the yeast simply doesn't have time to work.

   这也解释了为什么我最早烤的面包都是扁的。如果水太烫，酵母还没开始工作就可能被烫死。如果揉得不够，气体就会跑掉。如果你没耐心，酵母就根本没有时间发挥作用。

   Sources: Institute of Food Science & Technology (IFST), Love Food Love Science: "Raising agents: biological (fermentation)"; Exploratorium, "Science of Bread: Bread Science 101"

7. 07A Simple Way to Remember

   Here's a simple way to remember it: yeast makes the gas, gluten holds the gas, and heat makes the gas grow. Three stages, one fluffy loaf.

   这里有一个简单的记法：酵母产生气体，面筋留住气体，热量让气体变大。三个阶段，一个松软的面包。

8. 08Conclusion

   In conclusion, every loaf of bread is a small science experiment with living things. Next time you eat a slice, think about the tiny workers that made it rise. Thank you.

   总之，每一个面包都是一场用生物做的小小科学实验。下次你吃面包的时候，想一想那些让它膨胀起来的小小“工人”吧。谢谢大家。