How to Make Zakwas for Żurek (Polish Sour Rye Starter)

If you want to make authentic Polish żurek, you cannot skip this step.

You need zakwas ( the sour rye starter).

Zakwas is the fermented rye starter that gives żurek its signature tangy depth. Without it, you don’t have żurek. You just have broth with sausage. And that’s not the same thing. The good news? It’s incredibly simple to make. It just takes a little patience. And honestly, there’s something beautiful about letting flour, water, garlic, and spices slowly transform into something alive and deeply flavorful.

Let’s make it.

What Is Zakwas?

Zakwas is a traditional Polish fermented rye starter used to make żurek, the famous sour rye soup.

It’s made from rye flour and water, with garlic and spices added for depth. Over about 5 days, natural fermentation happens. Good bacteria develop. The mixture becomes pleasantly sour. Tiny bubbles form. The aroma deepens. That sour flavor is what defines the soup.

Zakwas is to żurek what sourdough starter is to sourdough bread. It’s the foundation. And once you make it once, you’ll wonder why you haven’t tried it before.

Ingredients

You only need a handful of simple ingredients:

• 1 cup medium or dark rye flour
• 3 cups boiled and cooled water
• 3-4 garlic cloves, lightly crushed
• 3 bay leaves
• 3 allspice berries
• 10 black peppercorns
• Optional: a few dried mushrooms for extra depth

How to Make Zakwas (Step-by-Step)

Step 1 – Prepare Your Jar

Use a large glass jar. Wash it well with hot water and soap. If you want to be extra careful, rinse it with boiling water to sterilize.

Clean jar = good fermentation.

Step 2 – Mix the Flour and Water

Make sure your water has been boiled and completely cooled to room temperature. If it’s too hot, it will kill the natural bacteria that make fermentation happen.

In the jar, whisk together the rye flour and water until smooth. Try to break up any lumps.

Step 3 – Add the Garlic and Spice

Add crushed garlic cloves, bay leaves, allspice berries, peppercorns, and optional dried mushrooms.

Step 4 – Let It Ferment

Cover the jar loosely. Do not seal it tightly. Fermentation produces gas, and it needs room to breathe.

Place the jar at room temperature in a dry spot away from direct sunlight.

Let it sit for about 5 days.

Stir it once a day and check on it. You should start seeing tiny bubbles after a couple of days. The smell will slowly change from raw flour to pleasantly sour and slightly garlicky. That’s exactly what you want.

How Do You Know It’s Ready?

After about 5 days, your zakwas should:

• Smell pleasantly sour (not rotten)
• Have visible small bubbles
• Taste tangy but not overpowering

Strain out the garlic and spices, then store the liquid starter in the refrigerator until ready to use.

During fermentation, the rye flour will settle at the bottom and a layer of liquid will form on top. You may also notice foam or bubbles along the surface. That’s exactly what you want to see.

Zakwas naturally separates as it ferments. Just give it a gentle stir once a day to keep everything active. Separation does not mean it failed.

What you don’t want is mold. If you see fuzzy green, black, or pink spots, discard it. But a clear liquid layer and sediment at the bottom? That’s healthy fermentation doing its thing.

Common Mistakes to Avoid

• Using hot water
• Sealing the jar tightly
• Not stirring daily
• Using white flour instead of rye
• Letting it ferment too long

This is simple fermentation. Respect the process and it works beautifully.

Common Questions:

How Sour Should Zakwas Be?

This depends on your preference. At 4–5 days, it’s balanced and mildly tangy. At 6–7 days, it becomes stronger and sharper.

I usually aim for around 5 days. That gives depth without overwhelming the soup.

How Long Does Zakwas Last?

Stored in the refrigerator, zakwas will keep for about 1–2 weeks. If it smells overly sharp or develops mold, discard it.

What Else Do You Use Zakwas For?

Most commonly, zakwas is used to make:

• Żurek (Polish sour rye soup)
• Barszcz biały (white borscht variation)

But żurek is where it truly shines.

If you’re ready to use your starter, head over to my full traditional Polish żurek recipe where I show you exactly how to turn this fermented rye into a bowl of comfort.

Can You Use Sourdough Starter to Speed Up Zakwas?

Yes. If you already have an active sourdough starter, you can use a small amount to kickstart fermentation and reduce the waiting time.

Traditional zakwas relies on natural fermentation from rye flour and the environment, which usually takes about 5 days.

Adding sourdough starter introduces active wild yeast and beneficial bacteria immediately, which speeds things up.

Option 1 – Add a Small Amount of Active Rye Sourdough Starter (Best method if you already bake sourdough).

• 1–2 tablespoons active, bubbly sourdough starter
  to your flour and water mixture on Day 1.

Keep everything else the same. This can reduce fermentation time to about 2–3 days instead of 5.

Important:
Use a rye-based starter if possible. A wheat starter will work, but rye keeps the flavor more authentic.

Option 2 – Add a Spoon of Mature Zakwas (If You’ve Made It Before)

If you have leftover zakwas from a previous batch, add 2–3 tablespoons to your new jar. This works like a “backslopping” method used in traditional fermentation and will dramatically speed things up. Fermentation may be ready in 2–3 days.

If you’re short on time but still want depth and authenticity, adding a tablespoon of active sourdough starter is completely acceptable and still very traditional in spirit. Polish kitchens have always adapted based on what was available. Fermentation isn’t about perfection. It’s about living culture.

Can You Buy Zakwas?

Yes, you can find bottled zakwas in Polish or European stores. But here’s the truth…Homemade tastes cleaner, fresher, and more balanced. Store-bought versions are often very sharp and sometimes acidic in a one-dimensional way. If you have 5 days, make it yourself.

Final Thoughts

There’s something deeply satisfying about making zakwas from scratch.

It’s simple. It’s old-fashioned. It requires no fancy equipment. Just flour, water, garlic, and patience.

This is how Polish kitchens have built flavor for generations.

And once you taste that first spoonful of real żurek made with your own starter, you’ll understand why this step matters.