Oxidative Aging Without Flor (Oloroso, Madeira Canteiro Method)

Oxidative ageing is one of the two types of crianza carried out in the Jerez region, according to the Consejo Regulador: the wine is stored and developed in wooden butts, where it undergoes slow, physico-chemical development influenced by surrounding conditions. The 2026 Pliego de Condiciones defines it as the type of crianza in which wines age without velo de flor and exposed to the direct action of the oxygen in the air. It contrasts with biological ageing, in which a film of flor yeast protects the wine from oxidation by preventing direct contact between the liquid and the air in the butt (Consejo Regulador). Beyond Jerez, IVBAM describes Madeira's canteiro as oxidative ageing in cask, and IVDP describes the gradual exposure to air that shapes older Tawny Port.

• Fortification to 17% ABV or more kills any flor yeast, committing the wine to purely oxidative development
• Butts are not usually filled to the top, and because the wood is permeable to oxygen, the Consejo Regulador explains, it admits a gradual but continuous dose of oxygen into the wine.
• Oloroso ranges from rich amber to deep mahogany in colour, and the Consejo Regulador notes that the darker the wine, the longer it has been aged
• Oxidative ageing can be done statically, without blending wines of differing ages, but the traditional system in Jerez is the dynamic criaderas y soleras system (Consejo Regulador)

Several changes run in parallel while the wine sits in cask. According to the AWRI, acetaldehyde levels increase as wines age due to chemical oxidation of ethanol, and above 125 mg/L acetaldehyde can impart 'sherry' and 'nut-like' characters. Over years in cask the wine is also enriched, the Consejo Regulador notes, by subtle, specific contributions from the wood of the butt, which is thoroughly wine-seasoned before being put into service. In Madeira, heat plays a further role: Decanter describes estufagem, used for inexpensive wines mostly made from Tinta Negra, as artificial heating that caramelises the sugars and lends something of a 'maderised' taste. In Jerez, evaporation through the butt, known as merma, accounts for losses of 3 to 5 percent per year of the total wine stored, according to the Consejo Regulador, and because the loss is essentially water, the wine's other components are continually concentrated.

• The AWRI lists 'sherry-like' and 'madeirised' among the sensory characteristics of oxidation, and notes that for some wine styles, such as sherry, oxidation is deliberately encouraged
• Oloroso can reach alcohol levels even above 20% simply as a result of long ageing, because the cask lets a good amount of water evaporate, concentrating the alcohol and the other components (Consejo Regulador)
• In Oloroso the content of both alcohol and glycerine increases over time, giving smoothness and a certain unctuousness on the palate (Consejo Regulador)
• Biological ageing works the other way: the flor consumes glycerine and volatile acidity and brings a substantial increase in acetaldehydes (Consejo Regulador)

The Consejo Regulador describes Oloroso as ranging from rich amber to deep mahogany, with a predominantly nutty bouquet of walnuts, toasted, vegetable and balsamic notes reminiscent of noble wood, golden tobacco and autumn leaves, and spicy, animal tones suggestive of truffles and leather. On the palate it is full flavoured, powerful and full bodied, smooth from its glycerine content, with an elegant dry finish. For older Tawny Port, IVDP describes the gradual exposure to air as concentrating and intensifying the original fruit, with honey and spices touched with aromas of dry peaches, hazelnuts and vanilla.

• Oloroso profile published by the Consejo Regulador (2026): 17 to 22% alcohol by volume, under 4 g/L sugar, 4 to 6 g/L total acidity and 8 to 10 g/L glycerine
• The 2026 Pliego describes Oloroso as old gold to dark mahogany, with aromas of nuts and wine-seasoned noble woods, possibly with caramelised or varnish notes, and a dry, balanced taste
• Amontillado ranges from pale topaz to amber with hazelnut and plant aromas; those aged longer under flor are paler, while in others the spice and wood of oxidative ageing predominate (Consejo Regulador)
• IVDP describes 20 Years Old Tawny as more developed and concentrated because the wine was aged in small oak casks, with aromas reminiscent of toasted vanilla and dried fruits

The solera and criaderas system in Jerez involves tiered scales of barrels: young wine enters the top tier and is progressively blended downward, with the floor-level solera being drawn for bottling and replenished from the criadera above. The Consejo Regulador calls the withdrawal of wine the saca and the topping up the rocío, with the youngest scale refreshed from the añada system. Under Consejo Regulador norms, the total volume of a solera system divided by the volume withdrawn from it each year must be greater than two, which keeps annual withdrawals below half of the system's volume, with the aim that no sherry reaches the market with less than two years of ageing. In Madeira, IVBAM sets out two ageing processes, estufagem and canteiro. Canteiro wines, named after the wooden beam supports (canteiros) on which the casks rest, age in cask, normally on the upper floors of the lodges where temperatures are higher, for a minimum of two years, and may be sold only after at least three years counted from 1 January of the year after the harvest. In estufagem, the wine is placed in stainless steel tanks heated by hot-water coils to 45 to 50 degrees Celsius for no less than three months, followed by a rest of at least 90 days at ambient temperature; IVBAM notes these are mostly blended wines.

• The preferred and most widely used Jerez cask is the 600 litre American oak butt, also called a bodega butt (Consejo Regulador); the 2026 Pliego limits ageing casks to 1,000 litres
• In solera wines aged non-biologically, the oxygen introduced during decanting operations accelerates the oxidative processes of maturation (Consejo Regulador)
• Blandy's ages canteiro wines in American oak casks in the warm attics of its lodge and uses the method for wines of a superior quality
• Madeira is fortified by stopping fermentation with wine alcohol at 96% vol, timed to the sweetness sought, giving dry, medium dry, medium sweet and sweet wines (IVBAM)

Oloroso is the Jerez wine of fully oxidative ageing: the 2026 Pliego classes it as a wine of exclusively oxidative ageing after the initial velo de flor disappears. Palo Cortado is also aged oxidatively; its young wines were first fortified to 15% for biological ageing and later refortified to 17% (Consejo Regulador). The Pliego recognises aged categories of over 12 and over 15 years, plus VOS (over 20 years) and VORS (over 30 years), and the Consejo Regulador requires a bodega to keep at least 20 litres in the ageing system for every litre of VOS it sells, and at least 30 litres for every litre of VORS. In Madeira, Blandy's, founded in 1811 by John Blandy with his brothers Thomas and George, ages its wines in lodges whose layout, shape and structure create a combination of temperature and humidity conditions stretching from the cellar up to the highest attics. For Port, IVDP groups Tawny Reserve, 10, 20, 30 and 40 Years Old Tawny and Colheita under the wood-matured Tawny style.

• Oloroso: fortified to 17% by volume, it ages in constant contact with oxygen as it descends through the criaderas and solera system (Consejo Regulador)
• Palo Cortado: similar to Oloroso but with a lighter structure, its alcoholic strength usually between 18% and 20% (Consejo Regulador)
• Madeira canteiro: IVBAM describes oxidative ageing in cask that develops intense and complex aromas; Decanter notes canteiro wines are aged in cask for anything from five to 50 years at ambient temperatures in warm lofts
• Colheita Port: single-vintage Tawnies aged in cask for a minimum of seven years (IVDP)

The Consejo Regulador notes that Jerez producers use one grape variety, Palomino, to make five different types of wine, and that the amount of fortification alcohol determines whether ageing will be biological or oxidative. Wines classified for Fino and Manzanilla are fortified to 15% by volume, enough for flor yeast to form but intolerable for other micro-organisms; the flor then covers the wine and prevents its oxidation. Wines for Oloroso are fortified to at least 17%; above 17% not even flor yeast can survive, so the wine loses the film and begins a slow but inexorable process of oxidation, seen in its gradually darkening colour. Amontillado bridges the two: it ages first under flor, then the flor begins to disappear and a second, oxidative stage gradually darkens the wine and enhances its concentration and complexity.

• Fino and Manzanilla: fortified to 15% by volume and protected from oxidation by the flor (Consejo Regulador); the 2026 Pliego sets Fino at 14 to 17% alcohol
• Oloroso: fortified to at least 17%, exclusively oxidative ageing, old gold to dark mahogany (2026 Pliego)
• Amontillado: biological then oxidative ageing, pale topaz to amber (Consejo Regulador); the 2026 Pliego sets it at 16 to 22% alcohol
• Glycerine: the flor feeds on alcohol, any unfermented sugar, glycerine and oxygen, while in Oloroso the glycerine content increases over time (Consejo Regulador)

Primary sources (Consejo Regulador Jerez-Xérès-Sherry, IVBAM, IVDP, AWRI, Blandy's): https://www.sherry.wine/documents/597/21052026_Pliego_Jerez_1wBQg8y.pdf, https://www.sherry.wine/sherry-wine/production/ageing, https://www.sherry.wine/sherry-wine/production/fortification, https://www.sherry.wine/sherry-wine/dry-sherry-wines/oloroso, https://www.sherry.wine/sherry-wine/dry-sherry-wines/amontillado, https://www.sherry.wine/sherry-wine/special-categories, https://www.sherry.wine/sherry-cask/types-of-sherry-wine, https://www.sherry.wine/news/abc-fortified-wines-jerez, https://vinhomadeira.com/o-vinho-madeira/vinificacao-e-envelhecimento, https://www.ivdp.pt/en/wines/port-wines/special-categories/, https://www.ivdp.pt/en/wines/port-wines/the-winemaking/, https://www.awri.com.au/industry_support/winemaking_resources/sensory_assessment/recognition-of-wine-faults-and-taints/wine_faults/, https://blandys.com/en/about-madeira-wine/, https://blandys.com/en/about-us/. Secondary source: https://www.decanter.com/premium/understanding-the-different-madeira-styles-413857-413857/. Last verified 2026-09-28