Culture yeasts have also been successfully employed in the manufacture of wine and cider.
The group has attained an importance of late even beyond that to which it was brought by Pasteur's researches on alcoholic fermentation, chiefly owing to the exact results of the investigations of Hansen, who first applied the methods of pure cultures to the study of these organisms, and showed that many of the inconsistencies hitherto existing in the literature were due to the coexistence in the cultures of several species or races of yeasts morphologically almost indistinguishable, but physiologically very different.
In the United Kingdom the employment of brewery yeasts selected from a single cell has not come into general use; it may probably be accounted for in a great measure by conservatism and the wrong application of Hansen's theories.
By this method several races of Saccharomycetes and brewery yeasts were isolated and described.
Certain yeasts exercise a reducing action, forming sulphuretted hydrogen, when sulphur is present.