Żurek is Poland’s sour rye soup. Its sourness comes from żur (also called zakwas na żurek, rye leaven): rye flour and water fermented for a few days until it’s tangy, then strained and simmered with stock, sausage, potato and marjoram, and served with a halved hard-boiled egg. It’s eaten year-round and is a fixture of the Polish Easter table, often with white sausage (biała kiełbasa). Bottled żur is sold in Polish shops, but it’s easy to make.
Żur: What Happens in the Jar
Rye flour mixed with water carries its own lactic acid bacteria and yeasts; within a few days at room temperature they sour the batter, as in a sourdough starter. A Kraków study that developed rye leaven for żurek found the best results with 1.5% salt and 0.5% garlic, and followed it through production and storage at 10 and 20°C (Surówka & Rzepka, 2024):
- The rye protein (secalin) broke down during fermentation and storage, freeing amino acids – part of żur’s savory depth.
- Those amino acids can become biogenic amines. The highest levels were putrescine (up to 117 mg/kg) and tyramine (up to 63 mg/kg); histamine stayed at or below 22 mg/kg even after 150 days.
- Leavens with more lactic acid bacteria had fewer amines and kept their flavor better.
In practice: a clean, quickly souring żur is the goal. Use fresh wholegrain rye flour, keep the jar at moderate room temperature, and refrigerate the żur once it’s sour.
Żurek vs Barszcz Biały
The names overlap. In many regions barszcz biały (“white borscht”) is made the same way as żurek, sometimes with a wheat- or oat-flour leaven instead of rye; red barszcz is a different soup, soured with fermented beets – see beet kvass. Rye is also behind Russian bread kvass. Romania’s sour ciorbă soups are soured with borș, a fermented wheat-bran liquid.
Is Żurek Gluten-Free?
No. Rye contains gluten, so żurek – homemade or bottled – isn’t suitable for celiac disease (NIDDK). Fermentation doesn’t remove enough gluten to change that.
Is Żurek Good for You?
It’s a hearty soup: the rye, potato and egg are filling, and the sausage brings most of the fat and salt. The soup is simmered, so the bacteria from the żur don’t survive in any meaningful number – don’t count it as a probiotic food. Because fermented rye leaven contains tyramine, people taking MAOI antidepressants, who are advised to limit tyramine-rich foods, should check with their doctor (Gardner et al., 1996). For a fermented vegetable that keeps its live cultures, Poles turn to raw sauerkraut and fermented dill pickles.