Zakwas na Żurek (Polish Sour Rye Flour Starter)

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Used as a thickening and potent flavor base for traditional Polish soups, Zakwas Żytni is a centuries old household tradition and as with prized sourdough starters, is something that was often passed on and handed down, taking some from a previous batch to start a new one. This traditional Zakwas na Żurek recipe is extremely easy to make, requires only flour, water and a few seasonings. Before long you will have that secret ingredient to achieving that authentic Polish flavor in your soups and sauces!

What is Zakwas na Żurek?

Also referred to by some as Zakwas Żytni, which is the more general term referring to “rye sourdough”, Zakwas na Żurek is specifically “sourdough for zurek” because it is most famously used to make the popular soup Żurek. Zakwas na Żurek is a lacto-fermented mixture made of water, rye flour, and usually some seasonings. It is left to sit at room temperature for about a week to allow the wild yeast and bacteria to develop. It’s made with a high ratio of water to flour so unlike regular sourdough starter which is thick and used to make bread, Zakwas na Żurek is a pasty liquid consistency that you pour into soups or sauces to add flavor while also serving as a thickening agent.

Zakwas na Żurek is readily available in Polish supermarkets and comes in jars. As easy as it is to make, even many Polish home cooks choose to buy ready-made Zakwas. I have heard, though I have not confirmed, that some well-stocked Polish deli’s in the U.S. sell it. However, even if you have access to ready-made, I strongly encourage you to make your own homemade Zakwas na Żurek because not only it is extremely easy, it’s cheaper and, as with things homemade, it also tastes better. Just be sure to plan at least 5 days in advance of wanting to use it.

Zakwas Żytni Ingredients

Traditionally the ingredients are kept few and simple. The standard flavor profile includes first and foremost garlic. Bay leaves and allspice form the other traditional flavors. You can increase or decrease the amount you use according to your preference but I find this is the perfect amount for a Zakwas to make Żurek soup. Here is what you’ll need to make your Zakwas:

• Water: As with all fermenting, in order for the wild yeasts and bacteria to form it is imperative that the water doesn’t contain chlorine, fluoride or other additives that will restrict their growth. If you’re on city water you will need to first boil the water and then let it cool. If you’re on well water you do not need to boil it first.
• Garlic: This is the most prominent flavor component and through the fermentation process the garlic mellows out and imparts a very savory, umami-rich smell.
• Bay Leaves: These contribute a balancing woodsy, earthy flavor.
• Allspice Berries: This imparts a flavor that is reminiscent of a combination of cinnamon, nutmeg and cloves with a pleasantly bitter, earthy and fruity flavor adding a wonderful complexity to the Zakwas. Be sure to use whole allspice, not ground.

How to Make Zakwas na Żurek

Let’s get started!

To make homemade Zakwas Żytni you will need a sterilized glass jar in addition to the ingredients. To sterilize the jar, place it in a pot covered in water by at least a couple of inches, and boil for 5 minutes.

I always like to grind my own flour from whole berries. If that’s something you’re likewise interested in I can wholeheartedly recommend the KoMo Classic Grain Mill. It’s German-made with a 12-year warranty, the quality and construction is amazing, and it’s a beautiful piece you can proudly display on the counter. I’ve had mine for years and it’s my kitchen workhorse. Alternatively (and much simpler and cheaper!) you can buy whole grain rye flour. It’s available in some grocery stores with well-stocked health food sections, in health food stores, speciality stores, and you can buy it online.

Place the flour in a sterilized glass jar. Add the water and give it a stir. Note: unless you’re on well water you will need to first boil and fully cool the water.

Add the garlic, bay leaves and allspice berries and give the mixture a stir.

Place a clean cloth or paper towel over the top of the jar and secure it with a rubber band or string. This way the zakwas can “breathe” without any critters getting in and you don’t have to worry about too much gas building up and cracking your jar.

Let the jar sit out of direct sunlight at room temperature. If it’s too cold the wild yeasts/bacteria will not grow. Once a day for 5-7 days, use a clean spoon to stir the contents of the jar.

After 5 days smell and taste the zakwas for the desire level of sourness and let it go another day or two if needed. (Unless it’s summer and really warm in my house, I let it go for 7 days.) If it’s properly fermented, when you jiggle the jar bubbles will fizz and trail up from the bottom of the jar to the top (see bottom right picture).

Remove and discard the garlic, bay leaves and allspice, screw a lid on the jar, and store it in the refrigerator to prevent it from fermenting further.

What Should Zakwas Taste and Smell Like?

Your fermented zakwas na zurek should have a bold and tangy, but pleasant smell. The smell should be rich and savory with umami undertones. The smell almost reminds me of walking into traditional butcher shops in Europe where they have the smell or smoked meats permeating the shop. It’s a very nostalgic smell to me. The zakwas should not smell or taste bitter or vinegary. Note that it will become more sour the longer it sits and sour doesn’t equate to “bad”, it just means over-fermented and will not taste pleasant. Once it has reached the desired level of fermentation, remove the garlic and seasonings, screw on a lid, and store it in the refrigerator to prevent it from continuing to ferment. If at any point smells “bad” or has any signs of mold, discard the batch and start again.

What About the Sediment at the Bottom of the Jar?

That’s part of your Zakwas Żytni. The clear liquid adds the flavor while the flour at the bottom of the jar is for thickening the soups or sauces. When I make Żurek soup I stir the whole jar before measuring it out to make sure I get the flour in there with it. If my soup needs to be a little thicker, I’ll scoop out some of the settled flour to add further thickening.

Storage and Freezing

Once your Zakwas na Żurek is ready, remove the garlic, bay leaves and allspice berries, screw a lid on the jar, and store it in the refrigerator to prevent it from continuing to ferment. It will keep for 2 weeks. As with sourdough starter, Zakwas can also be frozen for up a year. Let it thaw slowly, in the refrigerator or at room temperature.

How to Use Zakwas na Żurek

Zakwas na Żurekis the key ingredient in traditional Polish Żurek soup. This zakwas recipe makes 2 cups which is enough for 1-2 batches of Żurek soup, depending on whether you prefer your soup mild or boldly sour. In my Żurek recipe I recommend starting with a cup, tasting the soup, and then adding more as desired.

This sour rye starter can be used in other soups as well to add flavor and a touch of sourness and can likewise be added to sauces. Experiment with it.