Fermentation - Natural Sodas

Introduction

Making your own sodas at home can be as simple as adding carbonated water to a sweetened flavor base.  Fermenting sodas, while it takes a bit longer, results in more complex flavors accompanied by a soft effervescence and better nutrition.  The fermentation process harnesses the metabolic activity of yeasts to convert sugar into carbon dioxide (bubbles) and alcohol--but don't worry: homemade sodas contain less than 1%!  

The Basics:  To make your own soda, all you have to do is make a flavor base of fruit or herbal ingredients, add sugar, water, and yeast, and bottle it to produce carbonation.

Quick Reference
 Batch Size Fresh or Frozen Fruit Lemon Juice Water  Sugar Yeast
1 L (4 cups) 1 1/2 lbs 2 tbsp 2 cups 1/2 cup pinch
2 L (8 cups) 3 lbs 4 tbsp 4 cups 1 cup 1/8 tsp
4 L (1 gal) 6 lbs 8 tbsp 8 cups 2 cups 1/4 tsp
Materials
  • Large bowl
  • Fresh or frozen fruit
  • Lemon or lime juice
  • Water
  • Sugar
  • Salt
  • Champagne or lager yeast 
  • Fine-mesh strainer
  • Cheesecloth
  • Blender or food processor
  • Measuring cup
  • plastic soda bottle(s) 
  • Funnel
  • Mixing Spoon
Instructions
  1. Remove stems, seeds, and peels from fruit.  Chop into bite-sized pieces (berries can be left whole) and place in bowl along with lemon juice and any other desired flavorings (ginger, vanilla, herbs, etc.).  When using botanicals (as in rootbeer), a cotton steeping bag will save you the trouble of straining out the root and bark pieces later.
  2. Bring water to boil and remove from heat.  Dissolve sugar and a pinch of salt into water and pour over fruit.  Let steep at least 10 minutes.  When using dried ingredients, simmer over low heat for 20 minutes to extract flavors, then stir in sugar to make a flavorful syrup.
  3. While you wait, rehydrate the yeast in 1/2 cup water.  Sprinkle it over the water and set aside until foamy and bubbly.
  4. If making fruit soda, puree fruit with juice in food processor in several small batches.  Pour fruit juice through strainer lined with cheesecloth into another bowl.  For a really clear, pulp-free soda, do not press or squeeze juice out of fruit solids.  If using dried botanicals, remove steeping bag or strain solids out of syrup.  What you have so far is a concentrated, sweetened flavor base.  You can simply store the flavor base and mix a little with carbonated water whenever you wish to serve it.  Or, proceed with the following steps to carbonate the soda naturally with fermentation.
  5. Measure amount of flavor syrup then add enough cold water to bring total amount to desired full batch size less 1/2 cup.
  6. When mixture cools to below 30 deg. C (bath temperature), then stir up the rehydrated yeast and pour it into the flavor mixture.  Stir well to distribute yeasts evenly throughout. 
  7. Funnel soda mixture into plastic soda bottle(s); divide evenly if using more than one bottle.
  8. If necessary, top off bottles with water, leaving at least 1" headspace from top of each bottle.  Surprisingly, the more full the bottles are, the less carbonated they will get.
  9. Place bottle(s) out of direct sunlight and let ferment at room temperature for 2 days, or up to 4 days at cooler temperatures.  Fermentation is greatly affected by temperature, so exact times will vary. 
  10. Check bottle periodically by giving it a squeeze.  When it feels rock hard, refrigerate it and consume within 2 weeks.
Frequently Asked Questions

Can I make root beer using this method?

Absolutely!  The above instructions closely follow those of our Homemade Rootbeer Kit, which you might consider purchasing if you don't already have bottles, a funnel, sugar, yeast, and a reusable cotton steeping bag.  If you have everything you need and are just looking for a recipe, read on.  The amounts of sugar and yeast given in the instructions above will work whether you are making a fruit soda or rootbeer.  When making rootbeer, skip the lemon juice and simmer the following botanicals to make your flavor base: for a 2L batch, use 20g sassafras, 20g sarsaparilla, 1 star anise, 1 tsp wintergreen, 5 juniper berries and 1 cinnamon stick.  If you can't find these ingredients in your area, you can order the botanicals from us without having to purchase the whole kit; they're sold as a refill pack.  We offer the recipe for free to encourage you to experiment and play around with it so you get a beverage that is perfectly to your liking.  If you find our recipe too sweet, you can reduce the amount of sugar by up to 50% without effecting the fermentation process.  Enjoy!

Can I use the same glass swing-top bottles that I use for kombucha and water kefir?

Yes, with caution and experience.  It is recommended that you use plastic, at least the first few times, so you have a good idea of how long it will take to be fully carbonated.  But, remember, fermentation speed is greatly affected by temperature.  So, without being able to perform a "squeeze test," your decision as to when to refrigerate your soda will have to be based on experience and intuition.

Can I use baker's yeast if it's all I have around?

You can, but it's not recemmended.  The process will work with baker's yeast, but the resulting flavor won't be very clean.  Your soda will be noticeably more cloudy with yeast sediment and the flavor will be unpleasantly "yeasty."  It is highly recommended to use lager or champagne yeast because they will not taint the pleasant fruit or herbal flavors of your sodas.  Brewing yeasts can be found at homebrew supply stores and online retailers. 

Additional Resources

Christensen, Emma.  True Brews: How to Craft Fermented Cider, Beer, Wine, Sake, Soda, Mead, Kefir, and Kombucha at Home.  (2013)  An excellent reference that belongs in the kitchen of every foodie-homesteader.  The instructions above were largely adapted from her master recipe (p. 22).

Schloss, Andrew.  Homemade Sodas.  (2011)  Extensive manual of 200 recipes for fruit sodas, colas, root beers and more.


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