Sweet Potato Fly (Kvass) Fermented Soda Recipe

Did you know you can make fermented soda out of sweet potatoes? There’s a fermented sweet potato drink from Guyana curiously called “Sweet Potato Fly”.

It’s 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!

Check out the full video and subscribe to our YouTube channel. We appreciate your support!

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 you’ll 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 don’t 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 doesn’t try forming on top. Feel free to taste to see if you like the flavor as it’s fermenting. Note that you can also add a ginger bug starter at this step if you’d like to get it started quicker, but we haven’t 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 don’t 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 “burp” the bottle to release some of the pressure.

Sweet Potato Fly – What to Expect During Fermentation

During primary fermentation you’ll 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 you’ll 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

What’s the alcohol content of our homemade sweet potato fly? We’ve 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 – fg) * 131.25

Original Gravity (og): 1.05

Final Gravity (fg) (after 4 days): 1.044

ABV = (1.05 – 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!

It’s 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 don’t even need to have a ginger bug starter for this recipe, it couldn’t be any easier! Pick up a sweet potato from the grocery store, gather some of your holiday spices, and you’ll be in for a treat!

Let us know how it goes! Leave us a comment below and don’t forget to subscribe to our YouTube channel!

Have you tried Sweet Potato Fly?