Kvass made at home requires careful attention to detail, especially to temperatures. To avoid failures and frustration, purchase a thermometer that will measure liquids between 50-175 degrees F. You will also need to find a warm place that stays about 76-78 degrees in your kitchen or in a closet .
Be sure to use bread that is made only with rye flour, and that contains no food additives or preservatives. Kvass made from bread that contains oats or other grains is said to turn the fermenting liquid bitter. (Whole Foods markets imports a 100 percent sourdough rye bread from Switzerland and some Russian bakeries make a genuine rye bread without additives.)
Do not worry about using white sugar as most if it will be turned into beneficial acids.
The kvass should be stored in bottles with screw on tops or tops with wire fasteners. This recipe makes about 5 quarts.
1 pound rye bread, cut into 1/4-inch slices
1 1/2 cups sugar, in all
1 package dry active yeast
1 tablespoon unbleached white flour
About 1 dozen raisins
Spread the bread on cookie sheets and bake for about 30 minutes at 325 degrees. When cool, chop into 1/4-inch pieces in a food processor.
Bring 4 quarts of water to a boil and then cool to 175 degrees. Add the bread, stir well, cover with a lid and leave in a warm place (76-78 degrees) for 1 hour. Strain and reserve both the bread and the liquid.
Bring another 2 1/2 quarts of water to a boil, cool down to 175 degrees and add the reserved bread. Cover with a lid and leave in a warm place for 1 1/2 hours. Strain and discard the bread. Combine both batches of liquid.
Place 1/4 cup sugar and 1 tablespoon water in a small cast-iron skillet. Stir continuously over heat until the mixture turns golden brown. (Be careful not to burn it.) Remove from heat and gradually blend in 1/2 cup of the reserved liquid. Then stir this mixture into the entire batch of liquid.
In a small saucepan place 1 cup water and the remaining 1 1/4 cups sugar. Bring to a boil, lower the heat and simmer for 10 minutes, skimming once or twice. Stir this syrup into the reserved liquid and allow the mixture to come to room temperature (about 75 degrees).
Mix the yeast with the flour and combine with 1 cup of the liquid. Return this yeast mixture to the pot. Make an X of masking tape across the top of the pot. Cover the pot with 2 layers of cheesecloth or a clean kitchen towel and leave in a warm place (73-78 degrees) for 8-12 hours or overnight. Cool the kvass to about 50-54 degrees. Transfer to bottles, seal tightly and refrigerate for 24 hours. The kvass will keep in the refrigerator for 2-3 days.
In addition to its role as a refreshing drink, kvass is added to a number of typical Russian cold soups containing vegetables, sour cream and fish.
Adopted from The Art of Russian Cuisine by Anne Volokh, 1983.