What Increases Yeast Growth; Simple Science Experiment

Were your kids shocked when they learned yeast was alive? Maybe they don't even know yeast is alive yet, or maybe they don't believe you. I know my kids were initially surprised, but now they says "Hello little yeast," whenever they see me using them. 

Well, it just so happens that there is a new Zoey and Sassafras book out where Zoey needs to grow some small organisms called bips quickly. In a similar way, we decided to see if we could grow more yeast. Of course, our microscopic organisms don't help baby hippogriffs fly, but they make tasty bread!

This experiment can also be a fun one to show kids that yeast are living too! 

Supplies for Growing Yeast:

• 2 beakers or clear glasses
• Warm water (about 110° F)
• Dry Active Yeast
• Sugar
• Copy of Zoey and Sassafras Bips and Roses (optional but fun)

What Causes Yeast to Grow Rapidly?

To decide what causes an increase in yeast growth you first have to know what conditions cause yeast to grow at all. Like many other microorganisms a warm (but not too warm), wet environment is great for yeast growth.

So you will start by heating your water to between 110-115° F and pouring an equal amount into each glass. 

Next add the same amount of yeast to each glass. I think we used half a Tablespoon. 

Now, to one of the glasses, add some sugar; we used a teaspoon. 

So now you should have 2 containers with the same amount of warm water and the same amount of yeast, but one will also have sugar. Which do you think will grow more yeast?

The answer was obvious after 30 minutes, the sugar glass definitely had more growth. Maybe the water would catch up?

Nope, after an hour, the sugar glass was nearly full! Sugar definitely helped grow more yeast than warm water alone. Now you can see how yeast makes bread dough rise too!

At this point my daughter also put a drop of the mixture on a slide to look at under the microscope where she could see the yeast! 

Expand the Yeast Growing Experiment

Of course, my daughter wouldn't be herself if she didn't have another experiment she wanted to try. Typically it is adding water, but there is already water, so she wanted to try adding milk to a glass. She reasoned that milk has sugar in it even though it is a different type then table sugar, so maybe it would also feed the yeast. 

She started a new experiment set up the same way except this time, one glass had water and yeast, one had water, yeast, and sugar, and one had water, yeast, and milk (pictured in the center). 

You can see after about 30 minutes, there was no significant growth in the milk container compared to the water container.

I'm sure there are any number of things you could test to expand on this experiment too! You could try different temperatures or even smell like Zoey did (although I don't think yeast care). Find more simple science experiments HERE and more book activities HERE!