Farm Ferments: Sweet Potato Fly


One of my favorite lacto-fermented beverages is the delightful Sweet Potato Fly. It’s simple to make, delicious, and full of probiotic goodness. I’ve made it several times now, and it’s become a staple in our household. Interested in trying it? Read on!

Basically, the recipe consists of grated raw sweet potato, dechlorinated water, starter, lemon zest and juices, sugar, spices, and a clean crushed eggshell. I used whey from raw milk kefir as my starter, but it may be omitted and should still successfully culture (though it may take longer to finish). I also used a standard flat grater but in retrospect, think that a box grater would work more effectively. The raw sweet potato could also be grated in a food processor, but why deny yourself a nice little arm workout? Once the potato is grated and the starch rinsed off, it’s combined with the rest of the ingredients in a non-reactive fermentation container, like a lead-free glass jar. Stir it daily for a few days and watch it bubble. Once fermented to taste, it’s ready to be bottled, chilled, and enjoyed.


When the sweet potato fly is initially mixed, it smells just like a sweet potato pie: spicy, rich, and so evocative of autumn’s coziness. After a day or so, the mixture becomes cloudy and small bubbles are present at the top of the container…it’s alive! It’s always so exciting to see the tell-tale bubbles because they indicate activity: fermentation! I think it’s akin to seeing a seedling sprout from a seed; I’m farming microbes, too!


Wondering what it looks and tastes like when finished? When strained (I used a fine plastic sieve and pushed some of the grated potato down with my fingers to get as much of the liquid out as possible), the product was a nice peach-colored, slightly viscous liquid that retained the lovely fragrance of the spices. I think more thorough rinsing of the starch would reduce the viscosity, but I like it as it is. And the taste? As much as it smelled like sweet potato pie, it tasted even more like it! Probiotic (crustless) sweet potato pie in a glass. Heavenly.

Would you like to try making sweet potato fly? I used this recipe from Cultures for Health. I halved it to make 2 quarts (one half gallon). One modification that I make to the recipe is to cut the sugar back (I used about 75% of what the recipe calls for) – with the kefir whey, it still ferments actively and doesn’t end up being too sweet for my taste. The sugar feeds the microbes, though, so it’s important to leave enough fuel for them (and don’t substitute a non-fermentable sugar). If you have it on hand, adding a cinnamon stick instead of ground cinnamon would help prevent the spices from floating to the top, too.

Sweet potato fly would be a fun beverage for a holiday celebration, and could easily be made into a unique adult beverage. I can see it complementing the rich flavors of Thanksgiving and Christmas foods very well…but, really, a holiday’s not needed to enjoy some!

Did you make Sweet Potato Fly? Let us know how you liked it in the comments!

One thought on “Farm Ferments: Sweet Potato Fly

  1. I have seen a lot of recipes for sweet potato fly and really want to try it but can’t have dairy. Is there any reason I can’t substitute the whey for water kefir in the original recipe? Thanks!

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