film-forming yeasts, sometimes called film yeasts, flowers of yeast, or mycoderma, comprise a group of grape- and wine-associated species of wild yeasts, all of which require oxygen for their characteristic growth and metabolism. For this reason they appear on the surface of wine in barrels or vats that are not kept completely filled. Some, such as flor, being strains of Saccharomyces cerevisiae and genetically closely related to wine fermentation strains, can add desirable aromas and flavours, whereas other species, often referred to as ‘non-Saccharomyces yeasts’, produce off-flavours, while others have a relatively neutral sensory impact.
