Biological Aging Under Flor Yeast (Sherry Fino & Manzanilla)

Flor is a film of indigenous yeasts that forms on the free surface of wine after complete alcoholic fermentation; the OIV Code of Oenological Practices defines flor or film wines as wines biologically aged in contact with air through the development of such a film. In the Jerez region, the Consejo Regulador explains, several indigenous yeast strains have, through natural selection over the centuries, learnt to feed off the alcohol created during fermentation, so they keep working after all the fermentable sugar is gone. After alcoholic fermentation is complete, the yeast forms on the free surface of the wine, where, with the help of oxygen from the air, it survives by metabolising part of the alcohol, and the gradual reproduction of the cells produces a film-like culture that covers the whole surface. This veil prevents direct contact between the wine and the air in the butt, protecting the wine from oxidation.

• Casks are filled only about five-sixths full (JancisRobinson.com, 2026), deliberately leaving headspace so the yeast has access to the oxygen it requires to survive.
• The Consejo Regulador (sherry.wine, 2026) gives the flor-ageing fill as 30 arrobas (500 litres) in the standard 600 litre American oak butt, leaving a space of "two fists" of air on which the flor develops
• The 2026 Jerez pliego credits the historical fortification of wines for long sea voyages with a decisive role in the natural selection of the flor yeasts behind the region's biological ageing
• Beyond Jerez, JancisRobinson.com notes flor-influenced wines in the Jura, as vin jaune, and to a more limited extent in Gaillac.

The flor is not an inert layer but lives in constant interaction with the wine, according to the Consejo Regulador. Flor simultaneously consumes alcohol, any remaining unfermented sugar, glycerine and oxygen dissolved in the wine, according to the Consejo Regulador, and the 2026 Jerez pliego allows fino to be fortified during ageing to raise the alcohol when it falls through the action of the flor yeasts. The Consejo Regulador also lists volatile acidity among the elements biological ageing reduces, and credits a substantial increase in acetaldehydes with the sharp sensation on the nose that these wines gradually acquire. Fine lees, known as cabezuelas, accumulate gradually at the bottom of the butt over the years, and the trasegadores who move the wine must avoid churning them up or disturbing the film of flor.

• Acetaldehydes are the most prominent of the compounds the flor gives rise to, according to the Consejo Regulador's vinification page
• Wines aged exclusively under flor keep their initial pale colour and light, ethereal structure (Consejo Regulador), while oloroso, aged oxidatively, is described as smooth on the palate due to its glycerine content
• The 2026 Jerez pliego lists fortification during fino's ageing as a way to raise the alcohol when it falls through the action of flor yeasts; the 2026 Manzanilla pliego allows the same for manzanilla made as a liqueur wine
• The Consejo Regulador links the name flor (flower) to the way the film appears to flourish, looking most vigorous in spring and autumn, when temperature and humidity are ideal

Flor viability depends on maintaining alcohol within a particular range: the Consejo Regulador (sherry.wine, 2026) states that at 15% by volume the yeast can form the flor while other micro-organisms cannot develop, and that above 17% biological activity becomes impossible to sustain, so wines classified for fino and manzanilla are fortified to 15% by volume. Wines destined for oxidative oloroso aging are fortified to 17% by volume (Consejo Regulador, 2026) precisely to prevent flor formation. The 2026 pliegos set finished fino and manzanilla at 14 to 17% vol, and the Jerez text lists fino both as a 'vino' and as a fortified 'vino de licor', reserving fortification for the liqueur-wine category. Sanlúcar de Barrameda's coastal Atlantic climate provides cooler, more stable temperatures and higher humidity year-round, sustaining a thicker and more continuous flor than is possible in the warmer, drier interior of Jerez de la Frontera. Bodega architecture also plays a role: the Consejo Regulador (sherry.wine, 2026) describes Jerez bodegas as sometimes 15 metres tall at the central arch, their large volume of air supplying the flor with oxygen and acting as an insulating chamber that regulates temperature and humidity.

• Fino and manzanilla wines are fortified to 15% by volume, and oloroso to 17% by volume, which prevents flor and allows oxidative ageing (Consejo Regulador, sherry.wine, 2026)
• Wines first classified for flor ageing are re-assessed after six months to a year in butt, the sobretablas stage; where the flor has weakened or disappeared, they are fortified to 17% by volume for oxidative ageing as oloroso (Consejo Regulador, 2026)
• Manzanilla's biological ageing must be carried out entirely in bodegas in Sanlúcar de Barrameda, and the 2026 Jerez pliego excludes Sanlúcar as an ageing location for fino
• Decanter's Natasha Hughes MW writes that the drier, hotter conditions elsewhere in the Jerez region make the flor wax and wane, exposing the wines to a touch more oxygen than in Sanlúcar

Flor-aged wines are matured in the criaderas y solera system, a dynamic system of butts arranged in scales of different ages, which the Consejo Regulador calls the only viable method for successful biological ageing. Wine is periodically drawn from the oldest tier (the solera) for bottling, and each tier is replenished with younger wine from the tier above it, down to the youngest criadera, which receives fresh fortified wine. The Consejo Regulador names the extraction the saca and the topping up the rocío, and explains that the small quantities of young wine carry micro-nutrients the flor needs, supporting a vigorous film that might otherwise decline. When the flor begins to disappear, the wine moves into a second stage of oxidative ageing, and this two-stage process produces amontillado. The Consejo Regulador says each solera is made up of various scales, each composed of a particular number of butts, and in Sanlúcar the criaderas are known in the local vernacular as 'classes'. How often transfers take place and what proportion of wine is extracted are dictated by the wine's characteristics, and the Consejo Regulador (2026) requires the ratio of total stock to annual extraction to be greater than two.

• The tier at floor level holds the oldest wine, hence the name solera from suelo (floor); the tiers above are criaderas, numbered by closeness in age to the solera (Consejo Regulador)
• The 2026 Jerez pliego calculates a solera wine's average age as the total volume of stock in the system divided by the volume extracted for sale in a year
• Transfers dissolve a little oxygen into the wine, stimulating the flor to regenerate, and the yeasts' respiration then consumes it quickly (Consejo Regulador)
• The Consejo Regulador advises that sherry does not improve in bottle, reaching its best when withdrawn from the butt

Wines aged exclusively under flor keep their initial pale colour and light structure while acquiring aromatic notes that come from the yeast of the film (Consejo Regulador). The Consejo Regulador describes fino as bright straw yellow to pale gold, with a sharp, delicate nose hinting at almonds, fresh dough and wild herbs, and a light, dry palate. It describes manzanilla as pale straw with floral aromas recalling chamomile, almonds and dough, dry, fresh and delicate, with a lingering, slightly bitter aftertaste. The 2026 Manzanilla pliego requires at least two of white flowers, nuts or yeast (fresh bread dough) on the nose, and a dry, saline sensation on the palate. Both fino and manzanilla are the most delicate sherries once bottled, because leaving the cask removes the film of yeast that had prevented oxidation (Consejo Regulador, 2026).

• Fino: straw yellow to pale gold; almond, fresh dough and wild herb aromas; light, dry and delicate with an almond aftertaste (Consejo Regulador)
• Manzanilla: pale straw; chamomile, almond and dough aromas; dry, fresh and light with a slightly bitter finish (Consejo Regulador)
• Decanter's Natasha Hughes MW finds manzanilla usually a little brighter and fresher than fino, often with a salty note and a hint of green apple, and fino richer and broader on the palate
• Once opened, the Consejo Regulador advises keeping fino and manzanilla tightly corked in the fridge, and serving them chilled

Under the 2026 pliegos, fino is a wine of exclusively biological ageing within the DO Jerez-Xérès-Sherry, and manzanilla a generoso wine shaped by at least two years of biological ageing in bodegas in Sanlúcar de Barrameda. The base wine for fino and manzanilla is made from Palomino, fermented to dryness at roughly 11 to 12% ABV before fortification (Consejo Regulador, 2026). According to Tío Pepe's own site, Manuel María González Ángel entered the wine business in 1835, and a letter of 1844 requesting butts of the "exceptionally pale wine that you recommend so highly" is the brand's starting point for the first butts of Tío Pepe, which were well received in the United Kingdom; the brand says it now exports to 115 countries (tiopepe.com, 2026). In Sanlúcar, Bodegas Hidalgo La Gitana says it was founded by Pantaleón José Hidalgo in 1792, is run by the eighth generation of the family, and ages La Gitana manzanilla for 5 to 6 years under flor in soleras dating from 1792 (bodegashidalgolagitana.com, 2026). Bodegas Barbadillo dates its story to the purchase of its first winery, El Toro, in Sanlúcar in 1821, and its Solear technical sheet (2020) gives the manzanilla an ageing period of 6 years.

• González Byass 'Tío Pepe' (fino, Jerez): first butts dated by the brand to 1844; exported to 115 countries per tiopepe.com (2026)
• Bodegas Hidalgo La Gitana 'La Gitana' (manzanilla): Palomino Fino from Finca El Cuadrado in the Balbaína Alta pago; three years in the Bodega de San Fermín in Sanlúcar's barrio bajo, then two to three more in the San Luís bodega (bodegashidalgolagitana.com, 2026)
• Bodegas Barbadillo 'Solear' (manzanilla): 15.0% vol and a 6-year ageing period per Barbadillo's 2020 technical sheet, which describes the veil as formed by yeasts of the Saccharomyces cerevisiae genus
• Manzanilla Pasada is a manzanilla with a minimum average ageing of seven years that shows slight signs of oxidation from its prolonged ageing (Manzanilla pliego, 2026).

Primary sources (Consejo Regulador de las Denominaciones de Origen Jerez-Xérès-Sherry and Manzanilla-Sanlúcar de Barrameda, OIV, and producers' own sites): https://www.sherry.wine/sherry-wine/production/ageing, https://www.sherry.wine/sherry-wine/production/fortification, https://www.sherry.wine/sherry-wine/production/vinification, https://www.sherry.wine/sherry-wine/dry-sherry-wines/fino, https://www.sherry.wine/sherry-wine/dry-sherry-wines/manzanilla, https://www.sherry.wine/sherry-wine/dry-sherry-wines/amontillado, https://www.sherry.wine/sherry-wine/dry-sherry-wines/oloroso, https://www.sherry.wine/sherry-wine/production/diversity, https://www.sherry.wine/enjoying-sherry/conservation-serving, https://www.sherry.wine/documents/597/21052026_Pliego_Jerez_1wBQg8y.pdf, https://www.sherry.wine/documents/598/21052026_Pliego_Manzanilla_WA1VuvD.pdf, https://www.oiv.int/standards/international-code-of-oenological-practices/part-i-definitions/special-wines/flor-or-film-wines, https://www.tiopepe.com/int-en/our-story, https://bodegashidalgolagitana.com/tienda/manzanilla-la-gitana/, https://bodegashidalgolagitana.com/historia/, https://www.barbadillo.com/wp-content/uploads/2020/06/ficha-manzanilla-solear-baradillo-ingles.pdf, https://www.barbadillo.com/en/our-history/. Secondary sources: https://www.decanter.com/learn/advice/what-s-the-difference-between-a-fino-and-manzanilla-sherry-51784/, https://www.jancisrobinson.com/learn/wine-regions/spain/andalucia/jerez-xeres-sherry. Last verified 2026-09-28