Coffee & Rye Sourdough Kvass

Naturally fermented sourdough Kvass is a traditional Baltic and Slavonic drink, made from the black and rye breads traditional to the region, and is full of lots of good bacteria.  It is especially popular in Russia, the Ukraine, Georgia, Latvia and Lithuania, where it is often sold in the streets.  Naturally fermented sourdough Kvass is also found in some areas of China where there is a Russian influence.  In Poland, recipes would be passed down through families, and kvass is believed to have been made there since as early as the 10th century.

The drink has been common in eastern Europe since the middle ages and, in Peter the Great’s Russia in the late-seventeenth and early-eighteenth centuries, it was the most common non-alcoholic drink in every class of Russian society, which can’t be said for many other things.  I should note here that some alcohol is produced as the inevitable by-product of the fermentation.  The longer it is left to ferment, the more alcohol it will contain, but officially naturally fermented Kvass is classed as a non-alcoholic drink because the resultant alcohol levels are generally very low.

The kvass industry in Russia used to be huge, though it has inevitably struggled in modern society against the popular western soft drinks like Coca-Cola. Naturally fermented Kvass is such a staple part of Russian society that it features in lots of the most famous literature, including that by Chekhov, Dostoyevsky and Tosltoy.  There is also an expression in Russian – “to clamber from bread to kvass – which means to make ends meet or to be living on the breadline.  Even the very poorest families could make this drink, from the stale leftovers of their breads. It used to be predominantly a summer thing, but it is now more of an all-year-round one. With a wonderfully rich, dark colour – which depends itself on the colour of the bread used – it is deliciously earthy and  deep.  It can be layered with other flavours on top of the base ones, with herbs like mint or fruits such as berries and raisins.  As well as drinking it, kvass can be used in cooking, to add a deep tanginess to soups, for instance. Most modern kvass recipes use black or rye breads which are dried, baked or fried.  Sugar, fruit and ‘zakvaska’ – the kvass fermentation starter – are then added.  Like kombucha, it is lacto-fermented.  Often it will be served with the yeast still in it, which deepens its flavour.  It has a tangy, earthy, malted taste, quite similar to a deep, dark beer.  It is wonderfully refreshing and thirst-quenching, almost with a slight saltiness to it.  Running through it is a naturally sweet backbone, from the rye or black breads used to make it, with added sharp notes from the acids produced by the fermentation.  Though many naturally fermented drinks can be an acquired taste, they have layer upon layer of complex flavour which makes them endlessly fascinating.

As with other naturally fermented products, kvass is densely populated with beneficial bacteria from the starter.  There are many reported health claims stretching back through its history, however, the best explanation I can give about this is that the live microbes in the starter act as a probiotic.

My recipe of course uses sourdough bread. I usually use leftover rye bread such as from my Dark Rye & Treacle Sourdough or Chocolate Rye Bread but any sourdough works well.

Makes about 3 x 700ml bottles.

Ingredients

• About 350g of sourdough crusts
• 200g sugar, or 170g sugar and 30g black treacle for a deeper, richer flavour
• 1.5 litres black coffee at about 28-30^oC
• Ndali vanilla pod, optional
• 1 tablespoon sourdough starter

Equipment

• Large glass jar
• Muslin cloth
• 3 x 700ml glass or plastic bottles

Put the crusts into the large glass jar (the jar needs to be large enough to hold all the ingredients with space left to spare, because as the mixture ferments it will increase in volume). I sometimes toast the crusts first, to accentuate the Maillard reaction and get richer, toffee flavour notes. Add the sugar and stir to combine. Again, if you are looking for a deeper flavour, use a mixture of sugar and black treacle – it’s very good and gives an almost beer-like taste to the kvass.

Pour the black coffee into the jar, warming it first if necessary to help kick start the fermentation process. At this point, I sometimes add an old vanilla pod, if I have one leftover from making vanilla sugar. It adds some really beautiful top notes to the flavour and helps to balance out any beery notes. Then add a tablespoon of sourdough starter, I like to use my chocolate starter. It only needs this small amount to inoculate the mixture with wild yeasts and lactic acid bacteria.

Cover the jar with a loose-fitting lid and leave it to sit on the kitchen counter for about two days. It’s a good idea to put a tray underneath the jar because it can overflow if the fermentation really gets going. You also have to watch out for fruit flies. They are immediately attracted to the fermentation smell, so keep the lid loose, but covering the jar to prevent the fruit flies getting in.

Once the kvass has really started to fizz and you can see the bubbles in there, it is ready to drink as it is. And it’s very good at this stage, but I prefer to give it a secondary fermentation. Drain the bread off through a muslin cloth, straining out all the bits – this is a personal preference, some people like to see the bits at the bottom. I keep the drained bread to one side and use it in making my muesli rye recipe.

The strained liquid should be enough to half fill 3 bottles. It’s difficult to say exactly how much it makes because it’s subject to how much liquid the bread absorbs. The kvass should still be quite sweet but if, when you taste it, you feel that the sugar has all been used up, add another teaspoon.

To make ist stronger, and if there is enough room in your bottle you can further top each of the bottles up with cold, filtered coffee, put on a lid and leave them in a relatively warm environment for about 24-36 hours.

Now here’s the thing, you absolutely must ‘burp’ the bottles, because if you don’t the gas will build up during this secondary fermentation, and you could end up with an explosion. So set an alarm – it’s my key piece of advice for this secondary fermentation, to remind you to burp. Hold the bottle over the kitchen sink as you release the gas and, if you’re using glass bottles, have a clean tea towel wrapped around your hand as you do it, just in case the bottle shatters. My advice if it’s your first time making this kvass, is to use a plastic bottle, just to be on the safe side.

After 24 hours the kvass should be really fizzing away. If the room temperature is colder, it may take up to 36 hours. At this stage the coffee kvass is ready. Store it in the fridge, but remember to continue burping it at least once a day – I do it every morning as the kettle boils for my first cup of coffee.

Note: you don’t have to use coffee in this recipe. You could equally use tea or fruit juices. We often make kvass with our elderflower and rose, or strawberry and mint juices.