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, natural selection over the centuries has produced several indigenous yeast strains that have 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, deliberately leaving headspace that gives the flor a surface on which to develop.
• For flor ageing, the preferred 600 litre American oak butt is filled to 30 arrobas (500 litres), leaving a space of "two fists" of air on which the flor develops
• The historical fortification of wines for long sea voyages played a decisive role in the natural selection of the flor yeasts behind the region's biological ageing
• Beyond Jerez, flor-influenced wines are made 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. It simultaneously consumes alcohol, any remaining unfermented sugar, glycerine and oxygen dissolved in the wine, and under the 2026 Jerez pliego fino may be fortified during ageing to raise the alcohol when it falls through the action of the flor yeasts. Biological ageing also reduces volatile acidity and brings a substantial increase in acetaldehydes, responsible for 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
• Wines aged exclusively under flor keep their initial pale colour and light, ethereal structure, while oloroso, aged oxidatively, is smooth on the palate due to its glycerine content
• Fortification during ageing, to raise the alcohol when it falls through the action of flor yeasts, is permitted for fino under the 2026 Jerez pliego and for manzanilla made as a liqueur wine under the 2026 Manzanilla pliego
• The name flor (flower) refers to the way the film appears to flourish, looking particularly vigorous in spring and autumn, when temperature and humidity are ideal

Flor viability depends on maintaining alcohol within a particular range: at 15% by volume the yeast can form the flor while other micro-organisms cannot develop, and 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, which prevents flor. 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 bodegas have higher humidity all year and milder temperatures than the warmer, drier climate of inland Jerez, which helps maintain a deep layer of flor year-round. Bodega architecture also plays a role: Jerez bodegas are 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
• Wines first classified for flor ageing are re-assessed after six months to a year in butt, the sobretablas stage; where large gaps appear in the flor or it has disappeared, they are fortified to 17% by volume for oxidative ageing as oloroso
• 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, although stocks in biological ageing in Sanlúcar bodegas may still be used to make fino until 31 December 2030
• Elsewhere in the Jerez region, drier, hotter conditions 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, up to the youngest criadera, which is topped up with wine from the añada system. The extraction is called the saca and the topping up the rocío, and 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. 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 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
• Under the 2026 Jerez pliego, a solera wine's average age is 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
• Sherry generally 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 the yeast of the film gives them aromatic notes. Fino ranges from bright straw yellow to pale gold, with a sharp, delicate nose hinting at almonds, fresh dough and wild herbs, and a light, dry palate. Manzanilla tends to be 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. Fino and manzanilla are the most delicate sherries once bottled, because leaving the cask removes the film of yeast that had prevented oxidation.

• Fino: straw yellow to pale gold; almond, fresh dough and wild herb aromas; light, dry and delicate with an almond aftertaste
• Manzanilla: pale straw; chamomile, almond and dough aromas; dry, fresh and light with a slightly bitter finish
• 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, fino and manzanilla are kept tightly corked in the fridge, and served 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. Manzanilla is protected by its own Denominación de Origen Protegida, Manzanilla-Sanlúcar de Barrameda. The base wine for fino and manzanilla is made from Palomino, fermented to dryness at roughly 11 to 12% ABV. Tío Pepe traces its story to Manuel María González Ángel, who entered the wine business in 1835, and to a letter of 1844 requesting butts of the "exceptionally pale wine that you recommend so highly", and those first butts of Tío Pepe were very well received in the United Kingdom; the company exports to 115 countries. In Sanlúcar, Bodegas Hidalgo La Gitana 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. Bodegas Barbadillo bought its first winery, El Toro, in Sanlúcar in 1821, and its Solear manzanilla has an ageing period of 6 years.

• González Byass 'Tío Pepe' (Jerez): a letter of 1844 requested butts of the pale wine, and those first butts were very well received in the United Kingdom; exported to 115 countries
• 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
• Bodegas Barbadillo 'Solear' (manzanilla): 15.0% vol, a 6-year ageing period, and a veil formed by Saccharomyces cerevisiae yeasts
• Under the 2026 Manzanilla pliego, Manzanilla Pasada is a manzanilla with a minimum average ageing of seven years that shows slight signs of oxidation from its prolonged ageing.

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 2026-11-09