Investigate Thursdays – What makes bread rise?

For this week’s ‘Investigate Thursday’, we’re going to look at what makes bread rise!

To set up the experiment, you will need:
– a small bottle which holds about a litre
– 300ml warm water
– a glove or a balloon
– an elastic band
– a packet/3 tablespoons of yeast
– 1 tablespoon of sugar

Once you have gathered everything you need, we can begin:

Step 1: Mix your yeast, sugar and water together making sure that the water is warm but not hot.
Step 2: Pour this yeast mixture into the bottle.
Step 3: Tie your balloon or glove to the neck of the bottle using your elastic band.
Step 4: Leave the mixture for about 20 minutes and you should see the glove/balloon inflate. Do you know why this is happening?

Similar to last week, the answer to this lies in the gas called carbon dioxide. Yeast is a living microorganism and eats the sugar in the water producing carbon dioxide gas. As it eats more sugar, more gas is produced than can be held in just the bottle and so the balloon/glove inflates. This also happens when you add yeast and sugar to bread dough which makes the holes that you see in slices of bread.