At 1918, Sergei Alexandrovich Korolev worked at the Department of Microbiology and Zoology at the
Vologda Milk Institute. In 1920, he was elected professor of microbiology. He was engaged in improving the quality of dairy products and increasing shelf life (v1922, 1926). In particular, he proved that the yeast were not the agents of rancidity of butter (as some researchers thought), but on the contrary, they are antagonists of the problem and that most species of yeast occurring in oil retains in its mold. Methods of application of special yeast culture to combat mold oil, widely spread in practice to improve the safety of all types of oil. In 1923–24, S. Korolev, together with the professor G.S. Inihovym and students studied the microbiological and biochemical processes of maturation of a number of hard and soft cheese, produced in the
USSR. The work enabled the first time to make a harmonious synthesis of a unified theory of ripening cheeses. Prior to that, this theory put forward a Swiss scientist Freydenreyh, based on studies of only
Swiss cheese. Sergei Korolev is the author of
Technical Microbiology of Milk and Milk Products (1940), recognized as one of the best books in this branch of science. Also, he co-authored with G. Inihovym the textbook
Chemistry and bacteriology of milk and dairy products (1923). ==See also==