Żurek, also called Żur, is a traditional Slavic soup made of fermented rye flour. There is a similar one called Barszcz Biały and it has never been fully clarified what makes it different from Żurek. Every single time someone posts a Żurek or Barszcz recipe on a Polish website it sparks hot discussion in the comments section. People are really emotional about it and it’s really entertaining to read.
Anyway, Żurek is one of the reasons why you should visit an Eastern European shop. If you go there you will see bottles with a very strange looking mixture with no description, serving directions nor a recipe on it. A label just says: “Żurek” or “Żur”.
The said mixture, in fact, is not Żurek but fermented rye flour, an ingredient you need to make Żurek. One bottle makes one big pot of soup; let’s say 2-3 liters
To make the ferment at home you have to pour around a pint of warm, boiled water over 5 tablespoons of wholemeal rye flour, stir well, cover with a piece of linen cloth or paper towel and leave in a warm place for 5-6 days.
Sounds easy, but, in fact, it is a bit tricky. There is no salt added, so you must be very careful not to contaminate a jar with “bad bacteria”. I just pour boiling water into a jar and over a spoon that I am going to use. I empty a jar and wait for it to dry.
You can add pimiento and bay leaves to the mixture, but I don’t think it’s necessary as it’s added anyway when cooking the soup later. Also, I never put garlic to the ferment as recommended by some experienced Żurek makers, because I wouldn’t be able to recognize the progress of the fermentation by smell.
It is very useful though to add a piece of rye sourdough bread, or a tiny bit of sourdough matter or even a tablespoon of any kind of fermented brine from one of your jars with vegetables.
After 3 days, you should stir and smell the mixture. If it smells a bit sour, you are on the right track. But don’t despair if it doesn’t. Just repeat the stirring and inspect every day. If you keep the jar in a really warm place the ferment should be ready to cook after 5-6 days.
However, if you have never tasted Żurek nor smelled a proper Żurek ferment, I would suggest you buy it in an Eastern European shop to give you an idea of what to expect. It is quite easy to spoil the ferment and you don’t want to poison yourself, do you?!
On the other hand, anyone who has ever made sourdough bread successfully will easily recognize the smell of properly fermented flour.