What is kvass?

Shop-bought kvass varies by producer. Some products are made by diluting concentrate, mixing it with sugars and acidity regulators, and artificially carbonating it. Some products are made without fermentation. Other producers might use baker’s yeast for fermentation, which is then filtered out or killed by pasteurisation. Sugar content varies by recipe, so compare the ingredients and nutrition labels of individual products. Shelf life and storage depend on processing; a long best-before date alone does not show whether a drink has been fermented.

On the other hand, Quas is fermented using a sourdough starter culture where a rich community of over 100 types of live cultures and yeast are present. After the fermentation process, Live Quas is not filtered or pasteurised, meaning that you get over 500 billion live cultures with every can! We do not add preservatives, acidity regulators or artificial sweeteners. For a sugar comparison, use the specific drink’s nutrition label and the same serving size. We make fresh Quas weekly in small batches. Live Quas always needs to be stored in the fridge and has an approximate shelf life of six weeks from dispatch. Follow the best-before date on the can.

Genuine kvass is completely unique! You often see artificially formulated products, such as vitamin-infused water, or natural products like fruit juices. However, the amount of sugar present in natural juices is often quite high for modern diets (orange juice: 8 g; apple juice: 10 g; pineapple juice: 14 g; Coca-Cola: 11 g per 100 mL). Meanwhile, additives in artificially formulated zero-sugar products are well-defined but limited. In contrast, Quas is high in dietary fibre from chicory inulin, while containing only around 2.5 g of sugar per 100 mL. Most importantly, the traditional sourdough fermentation process naturally produces a complex, refreshing flavour profile that is uniquely attributed to authentic fermented products.

Quas is non-alcoholic, but it is still a fermented drink. Similar to fermented drinks such as kombucha and kefir, a small amount of alcohol can naturally be produced during fermentation. At Quas, we monitor and control alcohol content as part of production.

Kvass is made from fermented rye and barley. Ginger Quas also contains ginger, and Mint & Lime Quas contains lime juice and mint. No products of animal origin are used during the production process. Therefore, kvass is both vegetarian and vegan friendly.

No. Quas contains rye and barley, both cereals containing gluten. This applies to every current flavour of Quas. Check the can and the relevant product page for the full ingredients and allergen information.

Traditionally, kvass was made from oven-roasted rye bread. In this case, the dark colour comes from the roasting step. On a larger scale, malted rye grains are roasted instead of bread. This results in a slightly sour flavour of roasted rye breadcrumbs and brown colour that contribute to the unique features of the Original Quas.

Culture diversity matters because fermentation is not just carbonation and sourness. Different cultures help produce different organic acids, aromas and flavour compounds during the ferment. Many cultured drinks are built around one or two selected strains. Quas is fermented with a genuine sourdough starter, so the drink develops from a broader community of cultures working together. That is why the taste is layered, tart and alive rather than simple and sweet. We keep the claim to the product itself: culture diversity shapes the fermentation and the flavour.

The cultures in our sourdough kvass are dominated by lactic acid bacteria (LAB). Acetic acid-producing bacteria (AAB) are prominent in many studied kombucha cultures, contributing to tart or vinegary notes. Flavour varies with the recipe and producer. Kombucha and sourdough fermentation use different substrates and starter cultures. That difference does not establish a universal ranking of the microbial diversity of finished drinks. Studies have found kombucha cultures dominated by the Acetobacteraceae family, while the majority of the cultures in our sourdough starter belong to the Lactobacillaceae family (Gaggia et al., 2019; Frakolaki et al., 2020). In contrast, cereals (e.g. bread, grains, malts) that are used for the fermentation of kvass provide a natural environment for the cultivation of a rich, diverse microbial community!

If you enjoy kombucha, double-check the best-before date next time you pick a bottle. A recent study found that although yeasts in kombucha survived months of storage, the number of live acetic acid bacteria was significantly reduced after just one and a half months (Kallel et al., 2020). Those findings describe the kombucha samples and storage conditions studied, rather than a common shelf life for every brand. Live Quas has its own approximate six-week shelf life from dispatch and must be refrigerated.

Live Quas and unpasteurised kefir are fermented drinks that contain live cultures; processing can change the culture content of other products. Interestingly, they also both originate from the same geographical region: Eastern Europe. There are, however, some important differences. Quas is made from fermented cereal grains (rye and barley) using sourdough. Milk kefir is made from fermented milk using kefir cultures, while water kefir is usually made from sweetened water. Milk kefir can contain lactose, while water kefir has different ingredients. Check the specific product’s label if you need to avoid milk or lactose. Traditionally made kefir can also have a diverse community of live cultures, though its composition varies with the starter and production process.

The key differences stem from the starter culture that is used for fermentation (kefir grains vs sourdough). Research on particular traditionally made milk kefirs reported 22–61 bacterial sequence groups (operational taxonomic units), with Lactococcus spp., from the Streptococcaceae family, among the abundant genera (Bourrie et al., 2016). Only a few species of Lactococcus are commonly used as commercial starter cultures (Kondrotiene et al., 2020). In contrast, we have found at least 132 different types of microorganisms present in our sourdough kvass. This rich diversity is dominated by Lactobacillus spp. which belongs to the Lactobacillaceae family. Interestingly, the majority of widely studied live cultures belong to Lactobacillus spp. (Frakolaki et al., 2020). In kvass, there are at least 20 different types of cultures that belong to this group! These findings describe the products and methods tested, rather than a fixed culture count for every kefir. Different counting methods should not be treated as a direct ranking of all brands.

Kvass and beer are both produced during the fermentation of cereal grains. However, they are completely different products! Many beers are brewed with hops through yeast fermentation, which converts fermentable sugars into alcohol and carbon dioxide. The extent of fermentation and the remaining sugars vary with the style and production method. In some sour beers, lactic acid bacteria (LAB) are added to create sourness. Some beers are filtered or pasteurised after fermentation, while others use different methods. The process affects which microorganisms remain in the finished drink.

Production of low- or non-alcoholic beer, is somewhat similar, with the exception that the alcohol is either removed from the final product or the fermentation step is modified to produce limited alcohol content (Salanta et al., 2020). The presence of live yeast or bacteria in the packaged beer depends on its production and stabilisation method.

Live Quas is produced using mixed cultures of bacteria and yeast, and is not filtered or pasteurised. Other kvass products may be processed differently. In Live Quas, fermentation can continue in the can, meaning there are still fermentable sugars present in each can that microorganisms can feed off. This is also why you can taste a bit of sweetness in kvass compared to beer. Also, the traditional kvass recipe does not include hops, so all the rich fruity flavours are created by the bacteria and yeast during the fermentation!

A can of Quas (330 mL) contains around 59 to 63 calories. Energy content varies between beers, so compare the same serving size and the individual nutrition labels rather than assuming one average for the whole category. An illustrative comparison is available at (free-beer.co.uk). Most importantly, every can of genuine kvass offers a sophisticated, lightly tangy alternative to sugary soft drinks or beer!

Cultured drinks vary in their ingredients, production methods and culture content. Some are milk-based and others are plant-based; lactose, caffeine and sugar content depend on the specific product. Quas is a vegan grain drink, so compare it with another product using that product’s ingredients and stated culture information. In contrast, Quas is made using our natural 180-year-old sourdough starter culture, which contains over 100 types of bacteria and yeast! Each can of Live Quas contains over 500 billion live cultures, verified across batches. These figures describe Live Quas and are not a generic benchmark for every other cultured drink.

Commercial supplements often contain cultures that have been grown in the lab and then either formulated into a liquid product or dried into a powder and packed into pills. Growing the full diversity of microorganisms in a laboratory can be challenging (Lewis et al., 2020)! That observation does not establish the culture content of every supplement. The range of organisms varies with the formulation, and survival through processing and storage also depends on the organisms and the specific product. In contrast, we make Quas weekly in small batches with an approximate shelf life of six weeks from dispatch, when kept in the fridge. Live Quas is unfiltered and unpasteurised, so its cultures remain part of the drink. Keep it refrigerated according to the storage instructions. That is why we call it ‘Live Quas’!

Genuine kvass contains live cultures of bacteria and yeast that are still active. By lowering the temperature, we slow down their activity while still making sure they are alive and happy.

You might wonder how come Quas is not refrigerated during delivery? Fermentation is a complex process and we spent a lot of time optimising every parameter to make sure you get your order in the best condition. Our production process is designed in a way that allows kvass to be not refrigerated during delivery. However, you must keep Quas in the fridge at all times after receiving your order.

The shelf life of Live Quas is six weeks. Follow the best-before date on the can. Always remember that Live Quas can only be stored in the fridge. This is a relatively short shelf-life compared to other soft drinks or non-alcoholic beers. However, it ensures that whenever you decide to have a can of Quas, the live cultures and yeast inside are active and happy! As time goes on past the best-before date, the majority of sugars will be converted into organic acids, which will make Quas appear more sour than you might like it.

Quas is a live product, so you can think of every can as a miniature bioreactor! At low temperatures in the fridge, the live biological processes in Quas are slowed down, but they are still active. This means that even in the fridge, these live cultures and yeast continue slowly eating sugars and making organic acids, vitamins, enzymes, carbon dioxide and alcohol, among other things. As time goes on, Quas gets slightly more sour and less sweet. You should expect Quas to taste like genuine kvass within the best-before date. It may taste a little too sour to our liking after that, as the fermentation naturally continues.

The filtration or pasteurisation step is added to either physically remove live microorganisms from the product or simply kill them with heat. This helps to prevent food spoilage and extend shelf life. Think of a long life or UHT milk. However, the complex character of genuine kvass actually comes from the live cultures present in each can. At Quas, our goal is to make products of the highest quality using traditional fermentation, even if it comes at a cost of a shorter shelf life.

Because we counted them! We regularly take samples of Quas for analysis to make sure our kvass is of the highest quality. Part of the process includes counting the number of live cultures present in 1 mL of Quas. Because there are so many microorganisms in Quas, we first need to dilute it to be able to count them. After diluting Quas 1 million times (!), we transfer tiny droplets of diluted Quas onto a petri dish containing special growth media. A few days later, separate ‘colonies’ appear on the plate, where each ‘colony’ was started from a single microbe. Now you know why these are called ‘colony-forming units’ or CFU, in short. We then count all colonies and do some maths. On average, there are over 1.5 billion live cultures in 1 mL of Quas or over 500 billion CFU per 330 mL of Quas! Check out our Science page to see how it is actually done.

Quas is a sourdough fermented drink with 6.7g fibre per can. If fermented or high-fibre foods are new to you, start slowly: try one can on a day, then leave a few days before the next can, rather than drinking several cans at once. Pay attention to how it suits you, then build from there if you want to. The point is not to force a routine. It is to enjoy a complex, low-sugar fermented drink in a way that works for you.

Quas is made by real sourdough fermentation, so small amounts of alcohol can be present. This is not unusual: trace alcohol can also occur in foods and drinks such as bread, fruit juice, ripe bananas, kefir and kombucha. That context does not override NHS guidance. The NHS recommends not drinking alcohol if you are pregnant or planning to become pregnant, and does not give a recommended amount to drink during pregnancy. Quas is non-alcoholic, but it is still a fermented drink. We cannot make the decision for you. If you are pregnant, trying to conceive or breastfeeding, speak to your midwife, GP or another qualified healthcare professional.