 In Polish cuisine , white borscht ( barszcz biały , also known as żur or żurek , ' sour soup ' ) is made from a fermented mixture of rye flour or oatmeal and water . It is typically flavored with garlic and marjoram , and served over eggs and boiled fresh sausage ; the water in which the sausage was boiled is often used instead of meat stock . In the Carpathian Mountains of southern Poland , variants of borscht are also made in which the tart taste comes from fermented milk products , such as whey or buttermilk . Although the deep red color of beetroot borscht may remind those unfamiliar with Polish cuisine of blood , the kind of borscht that does contain animal ( usually poultry ) blood mixed with vinegar is dark brownish @-@ gray in color and aptly called " gray borscht " ( barszcz szary ) , which is a regional name of the Polish blood soup better known as czernina . 
