What is Kvass? The Russian “Water”

Like beer is to the Germans, Kvass is the national drink and a daily staple of East Slavic peoples, its importance dramatised in the words of poet Alexander Pushkin, “their kvass they needed like fresh air.” The linguistic root -kvas means “ferment” or “sour.” The original kvass is a ferment of stale black (rye) bread, water, honey, and sometimes yeast. The mildly fermented liquid is then filtered and consumed on its own or added to soups such as Borscht. It has a low alcohol percentage, between 0.7-2.2%. Variations of kvass number as many as the babushkas of Russia, and also depend on the region and season. For example, Ukraine has kvass made from fermented beets, while monasteries are famous for their yeast-free fruit and berry kvass. In tandem with the resurgence of interest in fermented foods, kvass is currently seeing a comeback in international realms.

Advantages of Kvass

Digestive benefits. Like all fermented beverages, kvass contains living probiotics, aids digestion, and is great to support gut health. Bacteria help to digest the problematic sugars and compounds that we often cannot digest, such as raffinose in broccoli, and sorbitol in apples, pears, and stone fruit, and oxalate in beetroot. Partly digested, the nutrients they contain are now readily accessible and absorbed. Simultaneously, the lactic acid bacteria also colonise the gut and keep it thriving.

Lower glycemic index (GI) compared to fresh form. Lacto-fermentation reduces the sugar content and GI of a vegetable/fruit. This is helpful for diabetics or those seeking to control the insulin levels, allowing them to enjoy the benefits naturally high sugar fruits such as beetroot and carrot.

Minimal fuss preparation. Kvass is the least fussy to prepare than other probiotic drinks, as it does not require the maintenance of a SCOBY as in kombucha, or kefir grains for kefir. While traditionally yeast is added, it can be easily wild-fermented without addition of yeast.

Two Ways to Ferment Kvass

Low salt brine. As kvass is mostly meant to be drank directly as a tonic beverage, using a light brine makes it more palatable and healthy. I found that 0.3-0.5% brine is sufficient. The addition of a starter culture such as sauerkraut juice helps kick off fermentation quickly and prevent off flavours.

Raw unpasteurised honey. Honey is usually added to fruit kvass, about 1 tablespoon to 4 cups filtered water, or 2% honey solution. The amount of honey can be adjusted depending on the sweetness of the fruit. For example, tropical fruit such as mangoes are typically higher in sugar and less honey is needed. Fruit kvass may also be prepared with brine.

In both methods, add the diced vegetable or fruit and desired herbs or spices to fill approximately one-third of your jar. Then fill the jar with the fermenting liquid (0.3% brine + starter culture or 2% honey solution), leaving 5 cm (2 inch) headspace to prevent pressure build-up from carbonation. The time required for fermentation depends on the item you are fermenting and ambient temperature. High sugar ferments like fruit kvass and root vegetables will be faster, as with a tropical climate. Check and taste vegetable kvass after 4-5 days, and fruit kvass after 2-3 days. Once it is sour to your liking, strain and proceed with a second ferment for carbonation (see below), or chill immediately.

How to use Kvass

Kvass offers a great canvas for experimentation, since you can use different types of bread, fruits, vegetables, honey, and spices in different combinations to create interesting flavours. The liquid of savoury kvass makes an excellent addition to soups and dressings, while the solids can be blended down into a dip or added to salads. Fruit kvass is a low sugar replacement for soda with added probiotic benefit.

Kahm Yeast in Kvass

Kvass, especially fruit kvass, is prone to Kahm yeast that appears as white specks on the surface of the produce. While Kahm yeast is harmless, and you can simply skim it off from the surface, below are some tips to avoid their unsightly growth in the first place:

Give your fermenting jar a gentle swirl daily to disrupt the surface and reduce the likelihood of Kahm yeast growth.
Place a cabbage leaf into the opening of the jar, which acts as a surface barrier and push any items that rise to the surface back underneath the liquid.
Fill your fermenting jar until almost full.

Secondary Ferment for Kvass

If you are the bubble-loving type, I highly encourage to continue with a second ferment by bottling the kvass with dried fruit or sweet juice and fermenting at room temperature for another day or two. The probiotics will continue to ferment on the sugars and produce more carbonation. It also makes it more palatable to kvass beginners. Pop, fizz and enjoy your glass of probiotic pizazz!