Flor

Flor (Spanish and Portuguese for flower) in winemaking, is a film of yeast on the surface of wine, important in the manufacture of some styles of sherry.

Normally in winemaking, it is essential to keep young wines away from exposure to air by sealing them in airtight barrels, to avoid contamination by bacteria and yeasts that tend to spoil it.

However, in the manufacture of sherries, the slightly porous oak barrels are deliberately filled only about five-sixths full with the young wine, leaving "the space of two fists" empty to allow the flor yeast to take form and the bung is not completely sealed.

A waxy coating appears on the cells' exterior, causing the yeast to float to the surface and form a protective "blanket" thick enough to shield the wine from oxygen.

A similar yeast to flor is used in the production of Szamorodni szaraz in the Tokaj wine region in northeastern Hungary and southeastern Slovakia.