In our previous two posts on teaching kids about yeast and fermentation, we covered food projects like bread, kimchi, sauerkraut. We also delved into dairy fermentation with kefir, yogurt and cheese. In this post, we’ll learn how natural sodas are made by fermenting yeast, which is actually the same way that alcohols are made.
WARNING: parents and teachers please be aware that kombucha and ginger ale recipes can create alcohol content as part of their natural fermentation process. Please take caution when serving these products to kids! Also: the bottles used to create the soda products below could explode, especially if they’re not made for this type of carbonation process. If that happens, take safety precautions, and watch out for shards of glass near kids!
Note that you can buy beer grade bottles and capping equipment from brewing shops for this science project, which may be safer than flip-top bottles or jars. Always keep the bottles or jars you use for natural carbonation in a covered box to contain any possible explosions.
With that said, let’s start learning about yeasts, fermentation and soda-making!
Teach kids about microbial symbiosis with kombucha
The kombucha ‘train’ is taking off among health nuts looking for a new way to get probiotics into their system. You can buy it in the stores, or you can make it at home with scoby, caffeinated tea and sugar.
The science lesson here teaches symbiosis, since kombucha likes multiple types of bacteria. In fact, “scoby” is actually an acronym for “symbiotic community of bacteria and yeast.” Plus, once that ‘healthy’ bacteria gets into your gut, more ‘good’ symbiosis takes place! You can also show kids how temperature affects the growth rate of these microbes, by leaving some in the fridge, and others at room temperature.
Since scoby is so old, dating back to ancient times, and because of the new bacteria it can introduce on each duplication, this lesson also brings about the concept of DNA changes over time.
The scoby fungi duplicates itself on every fermentation you put it through, which can take a few days (though this depends on the temperature in the environment). You can start a scoby from scratch, or you can find one from a regular home kombucha brewer.
For kids, the interesting part of kombucha is when you put it through a ‘second fermentation’ process. This is when the drink gets fuzzy, producing a natural (optionally flavoured) soda. But it kind of tastes like vinegar, so it’s not like the kids will have their expectations met when you use the word ‘soda’ here.
There has been some controversy around kombucha due to its ability to create alcohol when it sits too long on store shelves. Be aware that this product is living – especially if you make it at home. There aren’t really stabilizers preventing the further growth and fermentation of the soda, so it will keep ‘going’ until it becomes alcohol.
Teach kids about yeast fermentation with homemade ginger ale
This is a surprisingly easy and inexpensive project. Homemade ginger ale can also be turned into ginger beer, depending on the balance of sugars and days of fermentation you give it. But whatever you turn it into, it can teach kids a little history on how old-fashioned sodas were made using yeast found on the skins of ginger. The starter for this type of yeast food product is called ‘ginger bug.’ The term “ginger beer” in this sense isn’t necessarily actual, ‘get drunk’ beer. However, we should note that the live ginger bug can eventually bring this liquid to beer-level alcohol content.
Here is a lesson for kids on making ginger beer:
This lesson teaches a bit of history on ginger beer, as well as giving a recipe:
Here’s a fun ‘gross science’ lesson: in this process, you can also try ‘starving’ or ‘stressing’ the ginger bug by not giving it enough sugar in one of your control experiments. It will produce an awful rotten egg smell. Where is that smell coming from? Likely a sulphur-type gas. What is sulphur? How do you prevent it with ‘stabilization’? Bring on another science lesson!
Making ginger ale with yeast is quite similar to the concept of making kombucha. Here are simple recipes we found online to try:
Please remember, this fermented food product can also produce alcohol, like kombucha. We just want to be extra sure we’re making that disclaimer very clear!
To conclude: teaching kids yeast and fermentation science could go on and on…
As you’ve seen by the many resources we’ve provided in this three-part series, yeast and fermentation can teach kids a lot about biology, chemistry and microbial science. And, you don’t even need expensive materials, or a microscope to see it happening! Not only that, the extent to which fermentation happens can go further than the projects we’ve pointed out.
For example, while alcohol is not necessarily a kid-friendly experiment, it can be brought up as a procedural lesson on fermentation. Pickling other foods is another route to go with your science class. And, understanding the microbes in our body, along with the yeast that lives in and on our bodies, can be another biology or health science lesson (such as the explanation of yeast infections, or dandruff).
Whatever route you take, we hope you enjoy making and tasting these historic fermented foods as a result!