The veil of flor – El velo de flor

By 5 mayo, 2016Enodidáctica

Of all the miracles with which the world of wine can surprise its enthusiasts, the veil of flor is among those that draw the most admiration. What is it really and how does it transform wine?

One of the most commonplace microbiological accidents in the ageing of wines is the appearance of the so called flor, a kind of whitish film with a powdery appearance that covers the surface of the wine in the barrels. Its appearance is owed to the growth of undesirable yeasts, generally of the Candida, Pichia and Hansenula strains. It develops in wines that are low in strength, that are in contact with air – in barrels that are not completely full– and badly treated with sulfites. If not corrected in time, they lead to serious effects; the wine becomes insipid and develops a disagreeable smell of rotten apple.

The miracle of biologically aged wines means that the flor, instead of being an accident to be avoided, is something that is sought, cultivated, and protected. In the wineries that practice this kind of ageing, we find a flor that is very different, that fundamentally transforms and enriches the wine. The barrels that hold the wine destined to “suffer” the growth of the veil of flor are not filled to the top, since a chamber of air is necessary to allow the veil to develop correctly and breathe. We must not forget that the genesis of the entire miracle: the magnificent white albariza soils of the Marco de Jerez and the extraordinary suitability of the palomino fino grape. They determine the type of flor that will develop and survive on the different wines.

Albariza soil. The first driver of biological ageing. Photograph by Ramiro Ibáñez Espinar.

The flor is made up of yeast cells, which are unicellular fungi. To be clear, they are living creatures that are very small. At the end of the fermentation phase, they stay submerged and flee from the atmospheric stress of an environment with a certain volume of alcohol. They synthesize a compound, a lipid (fatty chemical) that forms a “biofilm” around the cell, making it lose density. As a consequence of that loss of density, the yeast begin to float, reach the surface, and initiate the breathing phase of the veil. Once on the surface, they start forming small colonies that, due to their shape, are reminiscent of flowers, from whence the name (flor being the Spanish for flower), and then join up so as to form the famous veil, which will expand and grow thicker and cover the whole surface of the wine contained in the barrels.


Left: Early stages of the yeast colonization. Formation of the first blooms. 1-2 days. Right: Early stages of the yeast colonization. The blooms join together. 2 weeks. Photographs by Ramiro Ibáñez Espinar.

Don’t get bored just yet. Stay with us. The best is yet to come. We have spent the last part of this article on the neophytes interested in putting into practice the theoretical part of this article by means of a journey of initiation. For now, we continue.

The major film yeasts that give form this layer in the biologically aged wines in the Marco de Jerez include the following, focusing on the most common so as to avoid a taxonomical labyrinth:

  • Saccharomyces beticus.
  • Saccharomyces cheresiensis.
  • Saccharomyces rouxii.
  • Saccharomyces montuliensis.

Left: Saccharomyces Montuliensis (Fino of 3 years). Right: Saccharomyces Beticus (Manzanilla of 3 years). Photographs by Ramiro Ibáñez Espinar.

The ability of these yeasts to float is owed to an extraordinary genetic adaptation that was developed through natural selection by lengthening the links of a gene known as FLO11. The increase of replications of said gene gave rise to the flotation ability and the adaptation and improvement in the ability to survive of the species.

These living beings, once they have guaranteed their respiration by rising to the surface of the liquid, need to feed themselves and, to do so, they take advantage of the nutrients that the wine provides, bringing about a series of important changes that we summarize in the following paragraphs:

  • The yeast consume, in a very notable way, glycerin, the dense, colorless, sweet substance that is responsible for the smoothness, unctuousness, and sensation of sweetness of many wines. As a result, biologically aged wines become extremely dry, the smoothness disappears in the mouth and there is an unmistakeable bitter emphasis.
  • They also consume alcohol as a source of carbon in order to grow, as a result of which the alcoholic strength diminishes and will have to be watched by the winery to avoid the so-called “desmayo” (fainting) of the wine in the barrel.
  • There is a significant reduction in volatile acid, which is formed by acetic acids responsible for vinegary aromas.
  • There is an increase in acetaldehyde (AcH), the most characteristic component produced by the yeasts in the wines, and which is found in a significant percentage in wines aged under flor. It leaves a characteristic aroma, generally described as stinging, reminiscent of nuts. It is the most volatile aromatic component. The boiling point of the AcH is only 21º-, and as such it is very noticeable. In some cases its aroma can take over the room with a glass of biologically aged wine in it.
  • The colour becomes clear, reaching pale or very pale straw yellow tones, as a result of the protection from oxygen offered by the veil of flor and the resulting reduction, which also consumes the limited oxygen contained in the empty space of the barrel.
  • Finally, cellular autolysis takes place. The enzymes of the yeast cells destroy the cells themselves, degrading the membrane and liberating the internal constituents into the wine. In this self-destruction, the yeasts “commit suicide” so that the wine “feeds from its mother”. The remains of the yeast accumulate in the bottle of the barrels and are known as “cabezuelas”. Contact with it enriches the wine to a greater level of aromatic and sapid complexity, leaving characteristic aromas of bakery, bread and sourdough, in addition to improving the tactile sensation by increasing its density and, in prolonged ageing, lend the wine a buttery character. The remains of the yeast are also reductive and protect the wine from oxidation.

Saccharomyces Beticus (12 years of biological ageing). Photograph by Ramiro Ibáñez Espinar

The end result of this miraculous process is a wine that is unmistakeable to the nose and on the palate. After this series of intense changes, one of the key words to describe the aromatic spectrum of a wine aged under flor is pungency. The principal component that determines the intensity of the pungent aroma is the aforementioned acetaldehyde. Biologically aged wines are described as pungent because they create a light, pleasing, and unique sensation of itching, burning or irritation – light and pleasing, remember – that make the aroma incisive, reminiscent of nuts and with salty airs.

A voyage of initiation

Those that try a biologically aged wine for the first time, a fino or a manzanilla for example, can be put off by the peculiar aroma –different to other wines that are, shall we say, “conventional”- and their special, flavour characteristics such as the dryness, the bitterness and the salinity. The majority of neophytes would describe the wines as “strong” or “very strong”. We know that it is a first impression that not everybody enjoys. For that reason, many people prove reluctant to try these wines again. Do you remember your impression the first time you tried beer? Do you drink beer now? Since the answer is probably yes, and moreover it is possible that you drink large quantities of beer, we will propose a healthy “exercise” for those wary of the great biologically aged wines. We are going to make it easy with a series of wines from the Marco de Jerez region that are affordable and easy to find almost anywhere in Spain and, we hope, abroad.

CastillodeSanDiegoCastillo de San Diego. Barbadillo. 3-4 euros: You might think I have gone mad recommending this wine in an article about the veil of flor because this has not been aged under flor. Why, then? It is a very solid example of a young white palomino fino wine without biological ageing. This way, you can get an idea of what a white wine from Marco de Jerez is before it goes through the changes brought about by the flor yeast. It is very direct, simple, clean, and very long. Large quantities are easily consumed.


muy-finaManzanilla Muy Fina. Barbadillo. 3-4 euros: Without leaving the same winery and as the next step in our particular stairway to knowledge of the veil of flor, we suggest this young and cheerful manzanilla. It is very interesting to compare it with the previous wine. By doing so, one understands how the flor transforms a wine in the early stages of evolution. You will see how the aroma becomes piercing and those saline and nutty notes we have spoken so much about start to appear.


tiopepeFino Tío Pepe. González Byass. 5-6 euros. An absolute classic. A wine of worldwide repute and class that has been on the market for 170 years. With this fino, we go from Sanlúcar to Jerez, from manzanilla to fino. With an average age of around 5 years, you will note the aldehydes we have spoken about before and you will notice primary aromas that give way as a result of the flor. There is more salinity, more nuttiness, and a more piercing character.


abAmontillado Viña AB. González Byass. 9-10 euros. We enter the world of the amontillados in what could be defined as a version of Tío Pepe with around 10 years of average age, of which approximately half have been spent under flor. If you don’t know what an amontillado is, we recommend a walk through our quick guide for beginners. In this wine, we observe the agony of the flor. AB is a smooth and elegant amontillado, that will allow us to experience the life of the biologically aged wines beyond the veil, when the latter cannot find the nutrients it needs to survive and disappears, giving way to a second oxidative type of ageing. You will find that the piercing quality starts to become smoother. You will still recognize the characteristics typical of the veil of flor, starting to overlap with touches of oxidative ageing like caramel. A fascinating and affordable wine.


After this little journey of initiation into the biologically aged wines, we hope that you will follow the path yourselves. It is a fascinating trip with different types and nuances all along the way. I started that way and I was hooked. You can follow our humble offering to the recovery of the prestige of these great wines in our dedicated section (in spanish). Remember that if the wines of the Marco de Jerez entrap you, they do it for good.

We would like to publicly express our gratitude for the collaboration of the Sanlúcar agrarian engineer and enology graduate Ramiro Ibáñez Espinar, one of the innovators and promoters of the silent revolution in the Marco de Jerez. Without his photographs, the article would not be the same.

We would also like to express our gratitude to for translating this article.

Lea este artículo en español.

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