Testing the effects of yeast!

The result of bread mixture with yeast.

The result of bread mixture with yeast.

As you can see we have one loaf of risen bread, it actually rose quite high. This is the loaf that contained yeast.  This risen loaf of bred was made with 1kg bread mixture.  The bread making machine used to bake our loaf had a limit of 750g.  Therefore, the top of the loaf did not bake because the mixture rose so high it hit the lid of the machine.  The mixture took up every bit of space in the machine.  A 1kg micture was obviously too much!!!



The result of bread mixture without yeast.

The loaf of bread that did not rise didn’t contain yeast.

This loaf was as hard as a rock, so hard in fact, Mrs Quealy couldn’t even cut it.


The crew responsible!

The crew responsible!

Our Year 6 students ate most of the loaf that had risen. It had a rather salty taste and felt like a sponge.  The uncooked top portion was quite moist and doughy, feeling a bit spongy, so we didn’t eat that bit!

Yes, Success!

In Science, we have been investigating the micro-organism, yeast. Yeast is a micro-organism because it is a single living cell and it is impossible to see with the naked eye.  We know yeast is alive because given the right conditions (temperature and food), yeast will grow and multiply.

Through our first experiment, we discovered that yeast produces a carbon dioxide gas and alcohol when mixed with water and sugar.  We came to this conclusion because we saw bubbles forming at the top of the yeast solution which was the gas.  This gas then inflated the balloon attached to the plastic bottle containing the yeast solution.  We could smell the alcohol when we held the neck of the balloon attached to the bottle to our nose.  When it was time to dismantle our experiment, we smelt the alcohol again when Mrs Quealy removed the balloon from the bottle.  It gave off a disgusting odour, it was YUCK!

Bottle 2 balloon inflated

Can you see why the other balloons did not inflate?  Why don’t you let us know your ideas and post a comment!  Maybe knowing what the ingredients of each bottle would help further understand!

Bottle 1 = yeast and water

Bottle 2 = yeast, sugar and water

Bottle 3 = sugar and water

Bottle 4 = yeast and sugar.

In our second experiment, (finished products pictured below) we wanted to find out what the best temperature was for yeast to be active.  We learnt that the best temperature for yeast to be active was 37 degrees – not too hot and not too cold, just right!

Science Experiment on PhotoPeach 

Here we are feeling very pleased with ourselves having just finished our second Science experiment investigating micro-organisms.


Bread Tasting

Today we investigated bread by comparing the texture, taste, odour and appearance of three different varieties: sourdough, Turkish pide and Mission Wraps.  We discovered that the breads were different in some aspects and fairly alike in others.  In studying the ingredients of all three bread types, we noticed that both the sourdough and the Turkish pide contained yeast, whereas, the Mission Wraps did not.  As it so happens, the breads containing yeast were high rise breads while the bread without yeast was flat bread!  Therefore, we conclude that yeast causes bread to rise.  Have you compared bread types?  If so, what did you discover?

Our investigation was fun and yummy (we got to eat all the bread). Just take a look at our photographs below:

Bread Tasting on PhotoPeach