Oat Kvass
A lightly tangy, refreshing probiotic drink made from oat groats and natural fermentation. In the first fermentation, the oats and sugar feed wild yeasts and lactic acid bacteria to create a mildly sour, digestive tonic. The strained liquid is then bottled for a short second fermentation to develop natural carbonation.
Takes 4 days 5 minutes
Serves 8
Ingredients
- 125 g 1 cup oat groats (whole, unrolled oats)
- 100 g ½ cup brown or white sugar, coconut sugar, or maple syrup
- 1 litres 4 1/4 cups filtered water
- 1 lemon
- Optional flavourings: small knob of ginger lemon peel, cinnamon stick, or vanilla pod
Instructions
Prepare the base:
- Rinse 125 g oat groats under cold water. Add them to a clean 2-litre glass jar or crock.
Add water and sugar:
- Dissolve 100 g sugar in 1 litre water. Pour over the oats, leaving a little headspace at the top.
Add flavourings (optional):
- Add a small knob of ginger, lemon peel, or a cinnamon stick if desired.
Ferment:
- Close the lid and leave at room temperature (20–25 °C / 68–77 °F) for 2–3 days. Stir once a day. You’ll start to see bubbles and a slight sour aroma — this means it’s fermenting. Taste after 48 hours: it should be gently tangy, mildly sweet, and slightly effervescent.
Strain:
- When the flavour is balanced (mildly tart with a hint of sweetness), strain out the liquid through a fine sieve or cheesecloth into a clean jug. Discard or compost the oats (or use them to start another batch once).
Bottle for carbonation:
- Pour the strained kvass into swing-top bottles, leaving about 3 cm (1 in) headspace.
- If desired, add 1 tsp sugar or a few raisins per 500 ml bottle to encourage fizz.
Ferment again:
- Leave the sealed bottles at room temperature for 12–24 hours, depending on ambient warmth. Check after 12 hours — when you see fine bubbles or hear a soft hiss when opening, it’s ready.
Refrigerate:
- Transfer to the fridge to halt fermentation. Chill before serving. The kvass will continue to develop flavour over several days.
Notes
Serving & Storage
- Serve cold as a light, refreshing probiotic drink — earthy, slightly sweet, and gently sparkling.
- Keeps in the fridge for 1–2 weeks.
- Open bottles carefully — natural carbonation can build pressure.
Notes & Tips
- Re-culturing: You can use 2 tbsp of the previous kvass (or a few tbsp of the oat mixture) to inoculate the next batch.
- Sweeter version: Add fruit (apple slices, dates, or berries) in the first ferment for a fruity note.