Name (also flor yeast) for special yeasts of the species Saccharomyces bayanus, capensis, cheriensis, fermentati, montuliensis and rouxii. These are able to convert sugar into alcohol in the first anaerobic phase (without oxygen) of fermentation. Afterwards, the flor yeasts can switch the metabolism to aerobic (with oxygen), so that a waxy, initially white coating is formed from alcohol and oxygen, which coats the individual yeast cells. This causes the yeast cells to rise to the surface of the wine and form a centimetre-thick layer (film) that increasingly turns brown. This protects the wine from air access and prevents further oxidation. To do this, it needs nutrients, which is achieved by adding small amounts of wine from young vintages. In this way, the yeast culture can be kept alive for years. The phenomenon is used in Spain in the solera system in the production of the sherry varieties Fino and Manzanilla. The resulting flavours impart the very typical nutty aroma.