Kvass is an awesome drink that is widely consumed in Russia and a lot of people there make it at home. While there are many recipes and HOWTOs available on the subject in Russian there is not so much information available for English speakers. Here follows my attempt to improve the situation.
There are probably hundreds of different kvass recipes and many methods of preparation. This one is the one that works for me. Ferment and enjoy at your own risk. Small quantities of alcohol may be present in the final product, but if it's more than 1-2 percent then you are doing it wrong.
Making kvass involves several stages:
- Preparation of source material
- Steeping this material
- Fermenting the resulting mixture
- Ageing the final product in the fridge
It also requires some patience as there is a fair amount of waiting involved. That said, with a bit of care you can time things around your working and sleeping hours. ;)
Stage 1: Making the "dough"
While kvass can be made from many things, this type is made from flour and malt. The types of flour and malt can vary (indeed this is the main difference between kvass recipes) and may include rye, wheat and barley flour and malt, or a combination these.
It is worth noting that most home-made kvass in Russia is actually made from dried rye bread. However, good bread here in London is quite expensive and also has very little malt in it, so I have opted to make my own instead.
This is the most time-consuming part of the whole process. Fortunately you only have to do it once to make many batches of kvass.
My recipe is very simple: 500g of rye flour and 50g or rye malt. Slowly mix the flour with boiling water (adding a little water at a time) and mix into a dough. Try to use as little water as possible. The dough must be hot – apparently it needs to be at least 60°C for the rye flour to undergo starch gelatinisation. I have no idea how to make dough so I just mix the stuff in a bowl with a spoon until there are no lumps before adding more flour. The end result should look like dough – if you don't know what that looks like ask someone who does, or buy some and look at it. ;)
Once the dough is done, mix in the malt and then let the dough stand for a few hours (or overnight) in a warm place. On a shelf in your boiler cupboard is a good place. Alternatively just wrap the container in some towels and leave it like that.
Transfer the dough to a baking tray. I recommend that the layer of dough is kept no thicker than 2-3cm, or the centre will not bake through. Bake the dough until it is dark brown but try not to burn it, since charred bread will not break down properly during fermentation. Once done, cut into 10cm x 3cm strips (since the inside will likely be quite moist) either roast further, or dry it somehow.
The more roasted the dough is, the darker and clearer your kvass will be. Lighter coloured dough will result in a paler, cloudier kvass (such as that used to make okroshka). Both are tasty. :)
The end product here is strips of dried dough, similar to cut up dried bread.
Stage 2: Steeping
To make 1.5 litres of kvass place 80g of dried bread in a pan and cover it with 800ml of boiling water, cover and allow to cool to room temperature. This will take several hours, so you can do it overnight. Strain (and keep) the resulting liquid, which should be a nice brown colour. Use the remaining solids to repeat the process one more time. Once the second batch is cooled combine with the first (keeping the solids in the mixture).
The product is a dark brown liquid with a layer of solids at the bottom. This is what we will be fermenting.
Stage 3: Fermentation (1)
Traditionally kvass was fermented in wooden barrels. Most Russians will use the ubiquitous 3 litre jar covered with a few layers of cheese-cloth. I use a plastic pitcher with a lid which works very well (the gap used for pouring allows oxygen to enter the vessel, which is important).
Unless you have access to a kvass starter (i.e. the solids left over from making the previous batch of kvass) you will need to use some form of yeast for your first batch. According to my research, the best culture is Saccharomyces exiguus (also known as S. minor) and it is found naturally in sourdough starter. I am fortunate to share my office space with a sourdough expert who kindly donated some lovely rye starter which I smeared on a piece of dried dough and added to the rest of the stuff. You can also use baker's yeast, providing it has no added nasty chemicals.
Add a table-spoon of sugar to the mix, stir well, cover and wait for the little guys to do their thing. Depending on various factors, this can take between 8 and 36 hours. Eventually, you will see that bubbles are regularly coming up to the surface, the liquid will start to smell and taste a bit sour and if you put your ear close to the jar you will hear fizzing noises. This is the sign that you can move to the next stage. Don't wait until your mix becomes very sour – or you will end up with vinegar. Also, the longer you ferment at room temperature the more likely you are to start making alcohol, which is not what we want.
Be aware that your very first batch of kvass (unless you used a starter) will taste different to the ones that follow: you will definitely be able to taste the yeast. Some people go as far as throwing the first batch away, but I drank mine anyway. ;)
Stage 4: Fermentation (2)
Strain the liquid into a 1.5l plastic bottle. Separately, dissolve 40g of sugar in some hot water and add this to your bottle. Add 4 washed raisins – these will help with making the kvass more fizzy. Seal the bottle and give it a light shake.
If you can, keep this bottle at room temperature for a few hours (but not too long). You will notice that the bottle starts becoming more firm.
Place the bottle in the fridge and wait for about 3 days. Dropping the temperature to below 10C changes the nature of the fermentation so that alcohol is no longer produced.
The remaining solids are your starter for the next batch. Transfer about 400g to a clean jar and put it in the fridge. It will keep for at least a week with no problems. Just add it all to your next batch of liquid instead of the yeast. Discard the rest, or give it to your friends.
Enjoy your kvass responsibly
At long last, remove the bottle from the fridge. By now the bottle should be rock hard. Open it very carefully, just a little to start letting the gas out. If you are not careful you will have a foam fountain that champagne bottles can only dream of!
Because your kvass has no nasty chemicals it will only taste good for a few days, so don't make too much of it at once.