Make Your Own Soda Pop
If you’ve worked concessions at a movie theater, you know how to make soda fizzy: Run a tube from a CO2 canister to your container of cola syrup and turn it on, and the gas creates bubbles in the cola. Most commercial soda companies use this “forced carbonation,” as do bars and fast-food restaurants.
The other two ways of carbonating, both forms of natural fermentation, use yeasts. In the first method, packaged yeast is added to your other soda ingredients. Then you bottle the soda and allow the yeast to consume the sugar. The yeast releases gasses in the form of bubbles. There is a risk of your bottles exploding if you add too much yeast. We have measured out exactly how much you need for our root beer recipe.
You can also ferment using only naturally occurring yeasts found in the air, as we did in our ginger beer recipe. As strange as it may sound, you simply expose your base sugar water to the air, and allow yeasts to battle for dominance. Eventually one strain wins, and that’s your yeast. You add the resulting bug, a frothy liquid that’s sort of like a sourdough starter, to the rest of your ingredients and bottle the mixture. Of the three methods, this produces the lightest carbonation, so there’s little risk of your bottles exploding.
“There’s no natural yeast that will hurt you, as far as I know,” says Madey. “I’ve never heard of anything.” Bacterial contamination is a possibility, but not any more so than when you’re making any kind of food.
To stop fermentation, all you need to do is refrigerate your bottles. Yeast goes dormant in cold temperatures.