They are wine strains of Saccharomyces cerevisiae family used in wine production and are the indigenous biological capital of each winery thus acting as terroir appendix.
Thanks to a specific gene, active only in the flor, they assume the unique ability to live two lives.
The first lies in the usual anaerobic-fermentative activity during which transform sugars into alcohol and carbon dioxide.
At the end of the process – in which oxygen is not used – all yeasts normally die because of alcohol that they themselves have produced, plummeting to the bottom of the container.
The “miracle” of flor is in a change of metabolism which reverses the action type aerobic-oxidative, thus resulting in a sort of resurrection, with the unexpected ability to use oxygen and feed on quell’alcol that was supposed to kill them.
The cell membrane is enriched with fatty acids which lightens the structure, making it hydrophobic, the flor can then aggregate into chains and rise to the surface to form the veil, an elastic biofilm often half a centimeter, whitish, wrinkled texture and crust fragrance bread.
In order for this to happen, it is necessary to leave the barrels partially filled 1/6 of their volume.
The florizzazione, characterized by a cell multiplication by budding, is unpredictable timing and outcomes: it can be activated by Christmas or by the warmth of spring or never, manifesting sometimes significant variations from barrel to barrel.
Consuming alcohol the flor oxidize ethanol and produce acetaldehyde, an aromatic precursor that binding to other molecules leads to the classic walnut hints, saffron, gentian, baked apple and smoked cheese.
They act even from biological deacidificatori, so much so that at some point begin to also feed dell ‘acetic acid that may be formed in scolma barrel.
The initial alcohol decrease (due to its consumption as a food) is more than offset by the simultaneous evaporation of water through the barrels, such as to determine an increase of the degree of alcohol also 1% per year.
The crucial point is that in the presence of powdered oxygen is a barrier that prevents him from being directed oxidation factor, relegating him quite a precondition for the nutrient-respiratory activity that characterizes the “second life” of flor.
Joint From the action of time and flor yeasts produce the reserve Bosa Malvasia (coppery brown bottle and gold cap).