Potatoes replaced turnips in borscht recipes, and tomatoes – fresh, canned or paste – took over from beet sour as the source of tartness. Eventually, both became staples of the peasant diet and essential ingredients of Ukrainian and Russian borscht.
Spanish conquistadors brought potatoes and tomatoes from the Americas to Europe in the 16th century, but these vegetables only became commonly grown and consumed in Eastern Europe in the 19th century. Ukrainian legends, probably of 19th-century origin, attribute the invention of beetroot borscht either to Zaporozhian Cossacks, serving in the Polish army, on their way to break the siege of Vienna in 1683, or to Don Cossacks, serving in the Russian army, while laying siege to Azov in 1695. The fact that certain 19th-century Russian and Polish cookbooks, such as Handbook of the Experienced Russian Housewife (1842) by Yekaterina Avdeyeva and The Lithuanian Cook (1854) by Wincenta Zawadzka, refer to beetroot-based borscht as “Little Russian borscht (where “ Little Russian” is a term used at the time for ethnic Ukrainians under imperial Russian rule) suggests that this innovation took place in what is now Ukraine, whose soils and climate are particularly well suited to beet cultivation. Jerzy Samuel Bandtkie‘s Polish-German dictionary published in 1806 was the first to define barszcz as a tart soup made from pickled beetroots. It may never be known who first thought of using beet sour to flavour borscht, which also gave the soup its now-familiar red colour.