How to Make Fruit Kvass with Summer Berries

Delicately fizzy with a gentle, berry-rich sweetness, this fruit kvass is delicious and refreshing. It's a perfect use for your summer fruit and makes a healthy drink that's low in sugar, brimming with nutrients, and rich in beneficial bacteria.

Fruit kvass in three glasses garnished with ice, strawberry and raspberry

What is it?

Kvass is a fermented drink from Eastern Europe. Kvass is typically made by fermenting rye bread in water; however, several variations exist including beet kvass and this fruit kvass which is made from berries.

Kvass made from berries (or other fruit) in absence of bread, was traditionally referred to as Moscow Kvass in Elena Molokhevets' A Gift to Young Housewives - a 19th-century tome that provides instructions on preparing thousands of traditional Russian dishes the way they would have been made prior to the industrialization of food in the 20th century.

What's in it?

This recipe for fruit kvass contains berries, water, and a touch of salt and honey. While it's a departure from the traditional method of packing fruit on a layer of straw in a barrel that Molokhevets calls for, you'll find that it's easy and works quite well.

Fruit gives the kvass flavor and a gorgeous vivid red color.
Salt provides a touch of electrolytes and supports a healthy environment for fermentation.
Honey feeds the beneficial bacteria that transform fruit and water into kvass.

Is it good for you?

While research on kvass (and fruit kvass, specifically) is scarce, the benefits of fermented foods and drinks are well-documented. Fermented drinks are rich in beneficial bacteria, and, when made from fruit, also rich in various antioxidants (that's what gives the kvass such a vivid color).

Kvass is rich in beneficial bacteria, specifically Lactobacillus casei, Leuconostoc mesenteroides, and Saccharomyces cerevisiae (1).
Fermenting fruit enhances its antioxidant capacity and fermented fruit juices are rich in probiotics (2).
Berries are rich in various beneficial compounds that support cellular health and combat inflammation (3, 4).

Tips

Fruit kvass is deceptively easy to make. If you can toss berries into a jar, and pour in some water, you can make it. It's extremely simple to make; however, there are a few things you'll want to keep in mind.

Use the best quality fruit. Fruit that is mushy, blemished, or at the end of its shelf life may introduce unwanted bacteria into your kvass or damage its flavor.
Burp your jar every day. Carbon dioxide builds up during fermentation, and burping your jar allows you to release the extra gas.
Shake your jar daily. This practice helps prevent mold from forming and potentially making your kvass go bad.

Pro Tip: Invest in flip-top bottles for fermented drinks and natural, probiotic sodas. These bottles capture the carbon dioxide that builds up during fermentation, making your soda naturally bubbly.

Rate this Recipe

5 from 7 votes

1 quart (4 servings)

Fruit Kvass

Vivid in color but delicate in flavor, this fruit kvass makes a delicious summer drink. It has a slightly acidic, effervescent edge that makes it super refreshing. This recipe is adapted from Strawberry Kvass from Elena Molokhovets' A Gift to Young Housewives.

Prep Time5

fermentation3

Total Time3 5

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Ingredients

1 cup strawberries (hulled and quartered)
1 cup raspberries
½ cup blueberries
4 cups water
½ teaspoon fine sea salt
2 tablespoons honey

Instructions

Dump the berries into a quart-sized jar.
Whisk the water, salt, and honey together in a medium-sized pitcher, and then pour over the berries, allowing 1-inch headspace and discarding any remaining brine. Seal the jar tightly, and shake.
Allow the fruit kvass to ferment at room temperature for about 3 days, shaking it daily and burping the jar twice a day. The kvass is ready when it lets out a hiss of air when you burp the jar.
Strain the kvass through a fine-mesh sieve, discarding the fruit. Transfer to a clean bottle and serve right away or store in the fridge up to 1 week.

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Variations

Substitute diced peaches, nectarines, plums or cherries for the berries to make a stone fruit kvass.

Swap red currants for some (or all) of the berries.

Swap diced apples for the berries and add a stick of cinnamon or a few pods of star anise.

Add herbs. Mint, chamomile, and anise hyssop would all be nice added with the fruit during the fermentation process.

Common Questions

Do I need to use a starter culture?

No. Berry and fruit kvass don't typically call for (or need) a starter culture; however, using a starter culture may speed up the fermentation process while also introducing specific strains of beneficial bacteria. Kombucha tea, jun tea, water kefir, or ginger bug all work as starter cultures if you wish to speed up the process.

Can my jar explode?

As fruit ferments, it releases lots of carbon dioxide. In a tightly sealed environment, the carbon dioxide has no place to go and so pressure builds within your jar. If the pressure becomes too high, your jar can explode. If you burp the jar every day, you'll release the excess gas and lower the chance of any mishaps.

Is it alcoholic?

Kvass is a naturally fermented drink, and as such, it typically contains a very small amount of alcohol - about 1.5%. For kvass that ferments an extended period of time, it may contain up to 2.5% alcohol by volume (1).

How do I store it?

Once you strain the kvass, transfer it to a bottle and store it in the fridge for up to 1 week.

How long does it last?

Fruit kvass will last about 1 week stored in a bottle in the fridge.

How do I know it's safe to drink?

If your kvass smells pleasantly sour and fruity, it's safe to drink. If you see visible signs of mold, if it has a viscous or unpleasant texture, or if it smells or tastes putrid, give it a miss. You can also check the acidity with PH strips intended for kombucha. For safety, it should reach a PH of less than 4.5. Mature kvass reaches a PH of about 3.8 (2).

How can I make it fizzy?

If you ferment your fruit kvass in a tightly sealed jar, it will be naturally fizzy when you open it; however, after straining you can pour it into a flip-top bottle and allow it to continue fermenting at room temperature for an additional day without burping. For safety, consider conducting the second fermentation in a closed environment, such as a closed cupboard or a cooler with a lid.

How much should I drink?

If you're not used to drinking or eating fermented foods, you'll need to start slowly to prevent unpleasant side effects that can occur in some people. I recommend starting with 2 tablespoons diluted in water and working up to drinking ¼ cup to 1 cup at a time.

Can I use frozen fruit?

You should be able to use frozen fruit in this recipe in place of fresh fruit.