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Soft drinks from Russia, Belarus, Ukraine, Baltic states, Poland
Fermented birch sap (berezovitsa, birch kvass)березовица (berezovitsa)
Birch sap, tapped in spring, holds about 1–2 % sugar and spoils within a day at room temperature. Set with oats, malt, rye bread or raisins, it ferments into a sour drink kept in barrels. In parts of NW Russia most sap is now drunk fresh and only what is left is fermented.
Fully documentedSoft drinks
Recipe
No fixed amounts recordedHousehold tradition with no fixed amounts.
oats laid on the sap (Lithuania); raisins sometimes added to start the fermentation (Pskov Oblast)
Start
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What changes:Sap drips from a tapped birch into a container
Step 1 of 4
Tap the sap in spring
Time
Not documented
Temperature
Not documented
Salt
None given
Acidity
Not documented
Which microbes the steps name, step by step
Lactic acid bacteria
L. reuteri
Output: fresh sap.
Flavour
Not documented
Texture
Not documented
Colour
Not documented
Microbes at work in this step
Not documented for this step.
Method
Measured measured in a studySet fixed by a specification or tested recipeReported one source reports itTypical a general value, not sourced for this fermentUnconfirmed not yet checked against a source
At a glance
Birch sap, tapped in spring, holds about 1–2 % sugar and spoils within a day at room temperature. Set with oats, malt, rye bread or raisins, it ferments into a sour drink kept in barrels. In parts of NW Russia most sap is now drunk fresh and only what is left is fermented. Limosilactobacillus reuteri does most of the fermenting.
Fermented birch sap starts from a thin tree sap with only about 1–2 % sugar instead of grain or fruit juice. Birch kvass replaces the water of bread kvass with sap.
Birch sap kvassSap fermented with barley malt bread or rye bread.
Oat-crust birch sap (Lithuania)Oats laid on the sap sprout into a crust that covers it while it sours.
Safety
Fresh sap spoils fast, in about a day at room temperature, so tap and process it quickly and keep it cold. Bacterial counts in sap rise late in the tapping season.
Birch sap has been drunk fresh and fermented in Lithuania for centuries and was widely tapped in eastern Poland in the 19th century. In the 1970s and 1980s a technology for sterilised birch sap appeared in NW Russia, and some lemon or orange started to be added.
[sancho2022] Sancho A.I., Birk T., Gregersen J.M. et al. 2022, Microbial safety and protein composition of birch sap, Journal of Food Composition and Analysis (abstract)paper