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.

   早安。我是一名化學老師，週末會和孩子們一起烤麵包。他們總是問我：「為什麼麵糰會變大呢？」今天，我就一步一步地講講其中的科學原理。

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.

   最基本的麵包只需要四種原料：麵粉、水、鹽和酵母。這個故事的主角是酵母，它是一種微小的生物。其實它是一種真菌，只由一個細胞組成。

   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.

   在第一個階段，酵母以麵糰裡的糖為食。它在進食的同時，會產生二氧化碳氣體和少量酒精。這個過程叫作發酵。

   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.

   但光有氣體還不夠，還得把它留住。麵粉和水混合後，小麥裡的兩種蛋白質會形成麵筋。揉麵會讓麵筋變得有彈性，就像一張由無數小氣球組成的網，把氣體留住。

   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.

   在烤箱裡，熱量會讓氣體膨脹，所以麵包會長得更大。酒精會蒸發，酵母也會被高溫殺死。所以烤好的麵包不會繼續變大。

   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.

   這也解釋了為什麼我最早烤的麵包都是扁的。如果水太燙，酵母還沒開始工作就可能被燙死。如果揉得不夠，氣體就會跑掉。如果你沒耐心，酵母就根本沒有時間發揮作用。

   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.

   這裡有一個簡單的記法：酵母產生氣體，麵筋留住氣體，熱量讓氣體變大。三個階段，一個鬆軟的麵包。

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.

   總之，每一個麵包都是一場用生物做的小小科學實驗。下次你吃麵包的時候，想一想那些讓它膨脹起來的小小「工人」吧。謝謝大家。