Kitchen Science 3-minute video · ages 4-8 · free coloring page
How does bread dough get bigger?
You make a small ball of bread dough and leave it in a bowl. An hour later, it is twice as big! How does bread dough get bigger?
3 min
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Free coloring page
The scene from the video as a coloring page, plus the three-sentence answer, the experiment, and a QR code back to this page. One sheet, US Letter, black and white.
The answer in three parts
Why?
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Yeast is alive!
It looks like a brown powder. But every little grain is a crowd of tiny living things, fast asleep. When they get some warm water, they wake up, and they are hungry!
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Yeast eat sugar and let out gas.
Flour is full of starch, and some of that starch turns into sugar. The yeast eat it, and let out a gas called carbon dioxide. It is a little bit like burping.
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A stretchy net traps the gas in bubbles.
When you knead the dough, the flour and water turn stretchy, like a net made of rubber bands. This is called gluten. It traps the gas in thousands of tiny bubbles. As the bubbles grow, the whole dough puffs up.
For grown-ups: Yeast are fungi, like mushrooms and molds, and each one is much too small to see. They work fastest when it is warm and slow way down in the cold, which is why bakers leave dough in a warm spot to rise. In the hot oven the bubbles get even bigger for a few minutes, then the heat makes the bread firm so it keeps its shape. It is far too hot for the yeast in there, so their job is done.
What's in bread dough?
- Flourfull of starch
- Waterwarm water wakes the yeast
- Saltjust a little
- Yeasttiny living things
A tiny experiment
Try it!
The balloon bottle
You need: a bottle, a balloon, warm water, a spoon of sugar, a spoon of yeast, and a grown-up to help
- Ask a grown-up to help. Put some warm water, a spoon of sugar and a spoon of yeast in a bottle.
- Stretch a balloon over the top, and wait.
- In about half an hour, does the balloon start to fill up, all by itself?
What happened? The yeast wake up, eat the sugar and let out gas. The gas fills the balloon, just like the bubbles in dough.
Did you know?
Cut a slice of bread and look closely. Do you see all those little holes? Every hole was a gas bubble that the yeast made. That is why bread is so soft and fluffy.
Bread made without yeast stays flat, like a tortilla or a cracker.
Your guide in this video
I'm Yeasty, a tiny bit of yeast. Today we will solve a puffy kitchen mystery!
Yeasty is a tiny cream-colored yeast with a little bud on its head. Yeasty's cousin is Fuzzy the mold!
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