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Bread kvass
Level 2 · some practice
Rye bread soaked in hot water, strained and fermented for a day with sugar and yeast. It comes out sweet and sour, fizzy, with a little alcohol.
- Sugar
- 22g per liter of water
- Time
- 24h
- Temperature
- 77–86°F
- Jar
- 6L
The golden rule: one day of fermenting, then into the fridge: the longer it goes, the more alcohol it makes.
No sign-up. We guide you step by step, from the scale to the fridge.
Reviewed October 26, 2026 · 30 facts, each with its source
You'll need
- Large pot that holds 4.5 liters
- Food thermometer
- Long spoon
- Large strainer and clean cheesecloth
- 6-liter glass jar (about 1.5 gallons), or two 3-liter jars
- Clean cloth and a rubber band
- Calibrated pH meter
- Kitchen scale
- Funnel
- Bottles made for carbonated drinks: soda PET, or glass made for fizz, with caps
Step by step
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Cut the bread into cubes and dry it
Wash the pot, the jar and the utensils in hot soapy water and rinse them well. Cut 500 g of rye bread into small cubes and let them air-dry until hard. Look them over carefully: if any of the bread is moldy, don't use it.
Tip: Throwing out moldy bread is a house rule, the same one the guidance gives for vegetables: anything damaged or moldy goes.
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Soak the bread in hot water, in two rounds
Heat 1.5 liters of water to 176 °F and pour it over the bread in the pot. Stir and let it stand for 30 minutes, stirring every 5. Add another 1.5 liters of water at 158 °F, stir and leave it 90 more minutes, stirring every 10.
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Strain it, add the rest of the water and cool it
Strain the liquid through the cheesecloth in the strainer. Add the last 1.5 liters of water at 158 °F. Let it cool to 77–86 °F in under 2 hours; if you need to, set the pot in cold water.
Tip: Don't add the yeast until it's down to 77–86 °F.
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Add the sugar and yeast, and leave it 24 hours
Dissolve 100 g of sugar in the liquid, about 22 g per liter of water, and crumble 20 g of fresh yeast over it. Stir, pour it into the glass jar and cover it with the cloth and a rubber band. Leave it for 24 hours at 77–86 °F; the study fermented it at 82 °F.
Tip: Just one day: left longer it makes more alcohol, and can reach 2.5% or more.
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Check the pH, strain it and bottle it
At 24 hours, check the pH with the meter: it must be 4.6 or below, and ideally 4.2 or below. If it's above 4.6, don't drink it: throw it out. Strain it again through clean cheesecloth, measure how many liters you have, and add 10 g of sugar per liter. Stir and fill the bottles with the funnel, leaving 3–5 cm (about 1¼–2 inches) of air at the top. Close them. Use soda PET bottles or glass made for fizz: the sugar in the bottles is what makes it fizzy.
Tip: The 4.6 and the 4.2 are house rules. Bread kvass sits close to that line: in the study, 4.15 on average, and 4.2 to 4.6 with additions.
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Straight into the fridge, and drink it within 7 days
Put the bottles in the fridge right away, at 39 °F or below: that slows the fermentation. Don't leave them out, or they can explode. Drink it within 7 days. Don't shake the bottles, and open them cold, slowly and away from your face.
Tip: The 7 days are a house rule. The study kept it 14 days at 50 °F, but as a trial, not as advice.
No sign-up. We guide you step by step, from the scale to the fridge.
Variations
The same method, a different flavor. Once you have this one down, try one of these.
What you'll see
Bread kvass is a drink with a rye bread aroma and a sweet-and-sour taste. It goes through two fermentations at once, one lactic and one alcoholic, of rye bread, sugar and yeast, and BCCDC classes it as a yeast ferment. There's no official guidance: this recipe follows a study published in 2024 step by step. The pH and the days in the fridge are house rules. It contains some alcohol.
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How to tell it's going well
- It contains alcohol. Up to 0.5% in the study; left longer, it can reach 2.5% or more. It's not for young children or during pregnancy.
- Just one day of fermentation. The alcohol depends mostly on the sugar and the microbes: don't add more sugar or more days.
- pH 4.6 or below before bottling, and ideally 4.2 (house rules). Above 4.6, throw it out.
- Moldy bread goes. And if mold appears in the jar, throw out the whole batch. Mold is usually green, blue, brown or black.
- A putrid smell: throw it out. The ferment has failed.
- Bottles made for fizz, straight into the fridge, at 39 °F or below. Without the fridge, they can explode.
- Drink it within 7 days (house rule). Open it cold and slowly, without shaking it: the cap can pop off and hurt someone.
Where every number comes from
Every number in this recipe comes from a food safety guide. We keep a copy of each source and quote its exact words.
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1
Lactic and alcoholic fermentation of rye, sugar and yeast
“Kvass is made through the following two processes: lactic acid fermentation and the alcoholic fermentation of rye raw materials (rye flour, dry rye bread, rye malt), sugar, and yeast.”
Foods (MDPI; Kaszuba et al.), via PubMed Central · Comparison of the Antioxidant and Sensorial Properties of Kvass Produced from Mountain Rye Bread with the Addition of Selected Plant Raw Materials (2024) · read on October 25, 2026
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2
A rye bread aroma and a sweet-and-sour taste
“Kvass is a refreshing beverage with a pleasant aroma of rye bread and a moderately sweet and sour taste”
Foods (MDPI; Kaszuba et al.), via PubMed Central · Comparison of the Antioxidant and Sensorial Properties of Kvass Produced from Mountain Rye Bread with the Addition of Selected Plant Raw Materials (2024) · read on October 25, 2026
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3
500 g of air-dried rye bread cubes, 30 minutes in 1.5 liters of water at 176 °F
“A portion of 500 g of mountain rye bread, previously chopped into small cubes and air-dried, was added to 1500 mL of water at a temperature of 80 °C, mixed, and left to stand for 30 min, stirring every 5 min.”
Foods (MDPI; Kaszuba et al.), via PubMed Central · Comparison of the Antioxidant and Sensorial Properties of Kvass Produced from Mountain Rye Bread with the Addition of Selected Plant Raw Materials (2024) · read on October 25, 2026
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4
Another 1.5 liters at 158 °F, 90 minutes
“Then, another portion of water (1500 mL) at a temperature of 70 °C was added, stirred, and allowed to extract for 90 min, stirring every 10 min.”
Foods (MDPI; Kaszuba et al.), via PubMed Central · Comparison of the Antioxidant and Sensorial Properties of Kvass Produced from Mountain Rye Bread with the Addition of Selected Plant Raw Materials (2024) · read on October 25, 2026
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5
Strained through cheesecloth, plus another 1.5 liters at 158 °F
“The mash was then filtered through a sterile gauze, and another portion of water (1500 mL) at a temperature of 70 °C was added to the filtrate.”
Foods (MDPI; Kaszuba et al.), via PubMed Central · Comparison of the Antioxidant and Sensorial Properties of Kvass Produced from Mountain Rye Bread with the Addition of Selected Plant Raw Materials (2024) · read on October 25, 2026
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6
100 g of sugar and 20 g of fresh baker's yeast
“To the filtrate, 100 g of sugar and 20 g of compressed baker’s yeast”
Foods (MDPI; Kaszuba et al.), via PubMed Central · Comparison of the Antioxidant and Sensorial Properties of Kvass Produced from Mountain Rye Bread with the Addition of Selected Plant Raw Materials (2024) · read on October 25, 2026
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7
Fermented at 82 °F
“left to ferment at a temperature of 28 °C (laboratory incubator)”
Foods (MDPI; Kaszuba et al.), via PubMed Central · Comparison of the Antioxidant and Sensorial Properties of Kvass Produced from Mountain Rye Bread with the Addition of Selected Plant Raw Materials (2024) · read on October 25, 2026
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8
24 hours of fermentation
“The fermentation time for both variants was 24 h.”
Foods (MDPI; Kaszuba et al.), via PubMed Central · Comparison of the Antioxidant and Sensorial Properties of Kvass Produced from Mountain Rye Bread with the Addition of Selected Plant Raw Materials (2024) · read on October 25, 2026
Show the remaining 22 claims
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9
Strained again through cheesecloth
“The next step was to separate the resulting kvass from the precipitate via filtration through a sterile gauze.”
Foods (MDPI; Kaszuba et al.), via PubMed Central · Comparison of the Antioxidant and Sensorial Properties of Kvass Produced from Mountain Rye Bread with the Addition of Selected Plant Raw Materials (2024) · read on October 25, 2026
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10
10 g of sugar per liter, bottled and kept 14 days in the fridge at 50 °F
“Sugar was added to the collected filtrate at a rate of 10 g/L of liquid, mixed and transferred into glass bottles (1000 mL), closed with twist-off caps, and left in a refrigerator at 10 °C for 14 days.”
Foods (MDPI; Kaszuba et al.), via PubMed Central · Comparison of the Antioxidant and Sensorial Properties of Kvass Produced from Mountain Rye Bread with the Addition of Selected Plant Raw Materials (2024) · read on October 25, 2026
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11
An average pH of 4.15
“The pH value of the tested control kvasses did not vary and averaged 4.15”
Foods (MDPI; Kaszuba et al.), via PubMed Central · Comparison of the Antioxidant and Sensorial Properties of Kvass Produced from Mountain Rye Bread with the Addition of Selected Plant Raw Materials (2024) · read on October 25, 2026
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12
With additions, 4.2 to 4.6
“higher values of the particular parameter were recorded in the range of pH = 4.2–4.6”
Foods (MDPI; Kaszuba et al.), via PubMed Central · Comparison of the Antioxidant and Sensorial Properties of Kvass Produced from Mountain Rye Bread with the Addition of Selected Plant Raw Materials (2024) · read on October 25, 2026
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13
Up to 0.5% alcohol in the study
“The presence of alcohol (Table 4) was found in the tested kvasses in concentrations not exceeding 0.5%”
Foods (MDPI; Kaszuba et al.), via PubMed Central · Comparison of the Antioxidant and Sensorial Properties of Kvass Produced from Mountain Rye Bread with the Addition of Selected Plant Raw Materials (2024) · read on October 25, 2026
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14
Left longer, it can reach 2.5% or more
“with longer stands, the alcohol concentration can reach 2.5% or more”
Foods (MDPI; Kaszuba et al.), via PubMed Central · Comparison of the Antioxidant and Sensorial Properties of Kvass Produced from Mountain Rye Bread with the Addition of Selected Plant Raw Materials (2024) · read on October 25, 2026
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15
The alcohol depends mostly on the sugar and the microbes
“Of particular importance is the proportion of sugar and the composition of the microflora”
Foods (MDPI; Kaszuba et al.), via PubMed Central · Comparison of the Antioxidant and Sensorial Properties of Kvass Produced from Mountain Rye Bread with the Addition of Selected Plant Raw Materials (2024) · read on October 25, 2026
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16
Bread kvass is a yeast ferment
“Kvass (rye bread), kenkey (cornmeal) and dosa (lentils) are ethnic yeast fermented foods.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 1: Introduction to fermented food safety (2024) · read on October 25, 2026
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17
Everything washed in hot soapy water and rinsed well
“Wash all surfaces and containers that will be used with hot sudsy water and rinse well before use.”
K-State Research and Extension (Kansas State University) · Taking a New Look at Fermented Foods (MF3491, June 2020) · read on October 20, 2026
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18
Anything damaged or moldy is thrown out
“Damaged, visibly mouldy vegetables should be discarded.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.1: Fermented Vegetables (August 2024, updated December 2024) · read on October 25, 2026
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19
Fermented vegetables must reach pH 4.6 or below
“Ensure effective fermentation and end pH of ≤4.6 is achieved.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.1: Fermented Vegetables (August 2024, updated December 2024) · read on October 25, 2026
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20
From 140 °F to culture temperature in under 2 hours
“from 60oC to 21-24°C within 2 hours”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.12: Kefir, milk and water (December 2024) · read on October 25, 2026
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21
3–5 cm of air in each bottle
“leaving a 3–5 cm air gap at the top”
Science in School (EIROforum), Dean Madden, National Centre for Biotechnology Education, University of Reading · Ginger beer: a traditional fermented low-alcohol drink (Issue 8, Spring 2008) · read on October 25, 2026
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22
Bottles that can take the pressure
“Glass bottles, cans or kegs should be resistant to acid leaching and pressure build-up.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.11: Kombucha and Jun (September 2023, updated December 2024) · read on October 25, 2026
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23
At 39 °F or below to stop fermentation
“Once fermentation is completed, kombucha and jun should be bottled and refrigerated to 4°C or lower to stop further fermentation”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.11: Kombucha and Jun (September 2023, updated December 2024) · read on October 25, 2026
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24
Without the fridge, bottles can explode
“Some jun and kombucha products can explode if not refrigerated.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.11: Kombucha and Jun (September 2023, updated December 2024) · read on October 25, 2026
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25
Caps can pop off and hurt someone
“If fermentation is not properly controlled, the container lids may come off under extreme pressure or containers may break. This poses a potential risk of injury.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.11: Kombucha and Jun (September 2023, updated December 2024) · read on October 25, 2026
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26
Do not shake, contents under pressure
“Precautionary statement labels on bottles are recommended to advise consumers “Do not shake. Contents under pressure.””
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.11: Kombucha and Jun (September 2023, updated December 2024) · read on October 25, 2026
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27
Not for young children or during pregnancy
“not a suitable beverage for young children or during pregnancy”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 2: Starter cultures and fermented food standards (August 2024, updated December 2024) · read on October 25, 2026
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28
If there's mold, throw out the whole batch
“If you confirm mold growth on any part of a ferment, it should be immediately discarded.”
UC Davis, Department of Food Science and Technology · Common issues with fermented fruits and vegetables (v1.0, 15-mar-2022) · read on October 20, 2026
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29
Mold is usually green, blue, brown or black
“Mold is typically green, blue, brown, or black in color.”
UC Davis, Department of Food Science and Technology · Common issues with fermented fruits and vegetables (v1.0, 15-mar-2022) · read on October 20, 2026
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30
A putrid smell means the ferment failed
“A putrid smell indicates a failed fermentation.”
UC Davis, Department of Food Science and Technology · Common issues with fermented fruits and vegetables (v1.0, 15-mar-2022) · read on October 20, 2026
