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 daysdays5 minutesminutes
Serves 8
Ingredients
125g1 cup oat groats (whole, unrolled oats)
100g½ cup brown or white sugar, coconut sugar, or maple syrup
1litres4 1/4 cups filtered water
1lemon
Optional flavourings: small knob of gingerlemon 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.
Stronger tang: Ferment the first stage for up to 4 days before bottling.
Join our Recipe Club with over 1000 delicious recipes today
Never Run Out Of Ideas Or Inspiration!
New Recipes Added Every Week
Easy To Follow Meal Plans
Available On Any Device
Only €3.99 Per Month
Recipe Club
Unlock the Ultimate Plant-Based Culinary Experience with The Happy Pear Recipe Club!
Dive into 1000+ mouthwatering recipes designed to nourish your body and tantalise your taste buds. Join our ever-growing, supportive community of food enthusiasts and take the first step on your journey to a healthier, happier you.
Get This Recipe & Over 1000+ Delicious Plant-Based Recipes
Never Run Out Of Ideas Or Inspiration!
New Recipes Added Every Week
Easy To Follow Meal Plans
Available On Any Device
Only €3.99 Per Month
Recipe Club Pricing
Whether it's monthly or annual, our Recipe Club membership gives you access to all our recipes in one place
Annual
€35.99
Monthly
€3.99
Happy Heart Challenge
Starting Monday 9th Feb!
Our Happy Heart Challenge is starting on
Monday February 9th – Feel more confident about your heart health,
energy and everyday choices in just four weeks.
