Did you know you can make fermented soda out of sweet potatoes? Thereâs a fermented sweet potato drink from Guyana curiously called âSweet Potato Flyâ.
Itâs sweet, slightly sour, and packed with a ton of flavor to delight your taste buds. Add in holiday spices and now you have a fermented soda that you can bring to holiday parties and wow all your friends!
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Sweet Potato Fly (Kvass) Fermented Drink
Originating in South American Guyana, sweet potato fly is a fermented sweet potato drink made by grating sweet potatoes, adding spices, eggshells, and citrus and letting it ferment for a number of days. I originally heard of this recipe in Sandor Katz awesome book The Art of Fermentation.
You can let your sweet potato fly ferment with the bacteria and yeasts that are already present in the sweet potato using wild fermentation or you can kick-start the process using a culture starter. This can include a ginger bug starter, water kefir, whey, and many other starters that are used to make fermented soda.
This sweet potato kvass can be a refreshing drink over ice and at the holidays makes an awesome stand-in for egg nogs and hot toddy cider drinks. Consider it another great seasonal drink that youâll come to love.
Sweet Potato Fly Drink Recipe (Simple & Holiday Version)
Makes 1 quart (or 2 bottles)
This homemade fermented soda is an awesome drink for the holidays. Try it out! If you donât like the holiday spices, just leave them out and serve over ice.
Equipment:
- 1/2 gallon jars or jugs for Primary Fermentation
- Fermentation lid <– These silicone lids work well for us
- (1) 16 oz. glass flip-top beer bottles <– We love these
- (1) 16 oz. heavy duty plastic bottle (such as Perrier or a soda bottle)
Ingredients for Sweet Potato Fly:
- 1/2 sweet potato, coarsely shredded (~10 oz.)
- 1 cup sugar (3/4 cup for simple version)
- 1 quart non-chlorinated water
- (optional) 1/4 cup Ginger Bug starter <– full post & video on how to make one
Holiday Spice Additions:
- 1/2 tsp. ground cinnamon
- 1/4 tsp. ground nutmeg
- 1/8 tsp. ground cloves
Grate fresh sweet potato and put in a large bowl.
Rinse grated sweet potato with non-chlorinated water a couple times or until the liquid becomes a little clearer. This is to remove a lot of the starch from the potato so it will have a cleaner taste.
Strain off liquid and add sweet potato to the 1/2 gallon jar. Add sugar, spices, and non-chlorinated water and stir until sugar is dissolved.
Add a cover or fermentation lid and ferment for 1-2 days. While fermenting, make sure to stir occasionally so mold and kahm yeast doesnât try forming on top. Feel free to taste to see if you like the flavor as itâs fermenting. Note that you can also add a ginger bug starter at this step if youâd like to get it started quicker, but we havenât needed a soda starter for sweet potato fly.
Strain off liquid when done with primary fermentation and pour the sweet potato fly into bottles to carbonate. If you donât like carbonation, simply skip this step. Watch out when carbonating! Sweet potato fly can build up pressure very quickly!
NOTE! – We like one of the bottles to be a plastic #1 soda bottle so we can squeeze the bottle to get an idea of how much pressure is building up. You might have to âburpâ the bottle to release some of the pressure.
Sweet Potato Fly – What to Expect During Fermentation
During primary fermentation youâll notice that after one day your grated sweet potato will look pretty even throughout and not much action should be happening except for small bubbles forming on top. If you added a starter culture like a ginger bug soda starter you might be seeing quite a bit more bubbling action.
After 48 hours of fermentation, our grated sweet potato began separating from the liquid and started floating to the top of the jar. This was due to all of the bubbles that were forming and causing the grated sweet potato to float. After stirring youâll see a lot of bubbles being released.
After 3 days of fermentation the soda is definitely separating more from the sweet potatoes and the liquid has become a slight orange white color. After tasting, we decide that it probably tastes best if you only ferment for one to two days but it still tastes good!
Sweet Potato Fly Alcohol Content
Whatâs the alcohol content of our homemade sweet potato fly? Weâve had this question for a while along with the alcohol content of ginger ale so we picked up a hydrometer to measure the alcohol content.
We measured the gravity of our sweet potato drink before and after the fermentation process and plugged it into the generally accepted formula:
Alcohol By Volume (ABV) Formula
ABV = (og â fg) * 131.25
Original Gravity (og): 1.05
Final Gravity (fg) (after 4 days): 1.044
ABV = (1.05 â 1.044) * 131.25 = 0.79% ABV
After about four total days, we have a fermented sweet potato fly soda estimated at just under 1% alcoholic content. Wow!
Try this Fermented Sweet Potato Drink!
Itâs so much fun to try out all of these homemade fermented drink recipes! From ginger ale, to watermelon soda, to this slightly sour sweet potato fly, every fermented soda has its own unique characteristics.
Since you donât even need to have a ginger bug starter for this recipe, it couldnât be any easier! Pick up a sweet potato from the grocery store, gather some of your holiday spices, and youâll be in for a treat!
Let us know how it goes! Leave us a comment below and donât forget to subscribe to our YouTube channel!
I just watched the youtube video (some of your product links are broken, FYI). As soon as I was done I put together the holiday recipe. I am excited to see how it turns out.
Thank you so much for catching that Jack! It looks like the ones that we bought have been taken down from Amazon. If you still want to check them out, I think this version might be even a little better than the ones we have: https://amzn.to/2E86ryK
We hope that the holiday sweet potato recipe turns out for you! Thanks again!