Maderisation is a process that involves the heating and oxidization of a wine, resulting in a darker colour and an altered taste. The term is named after the process used in the production of Madeira wine; where it occurs while the wine is in the barrel. The resulting wine darkens in colour and acquires a unique character.
Outside Madeira wine, it is generally seen as a fault, but in controlled measures is desirable in certain dessert wines where it occurs over the course of lengthy bottle aging.
Maderised or oxidised wine - is derived from the French word Madère, meaning Madeira and thus madérisé, meaning oxidised, the process by which Madeira wine is deliberately made. The colour of a white wine will have a yellow to pinkish hue, whilst a red will turn tawny.

 

Oxidation is caused by the reaction of oxygen with various wine components. When oxidation occurs during the winemaking process, the winemaker is able to treat the condition by using sulphur dioxide or ascorbic acid. However, there are many styles of wine which are deliberately oxidised, such as Madeira, Sherry, Vin Santo, Rancio, Vin Jaune and other styles vinified ‘sous voile’ - literally under a veil, for example the thin film of yeast referred to as flor which forms on the surface of Fino Sherry.
The style of Madeira wine was previously achieved by long ship journeys to tropical countries. The wine endured a hot climate that changed its character, the so-called maderisation. In the 18th century ‘estufajes’ were built. These are vessels in which the wine is heated for 3 months to a minimum of 40ºC up to a maximum of 50ºC. The wine is slowly brought to temperature, with a maximum of 5°C per day.
The creator of this system was Pantalão Fernades, was inspired by the ancient Roman baths. After this warming up follows the ‘estagio’ a resting period from at least one year. The wine will stay here for 1 year up to 10 years. There are two types estufa: the ‘Armazen the colour’, warming in wooden barrels, and the ‘cubas the colour’ warming in plastic of ceramic vessels of 20,000 to 40,000 litres.
Bual or Boal in Portuguese is a name given to a number of different varietals grown on the island of Madeira and also refers to the style of wine produced. The grape has a high acidity which works extremely well when put through the 'maderisation' process where the wine is fortified and then slowly cooked in the barrel over a number of years (traditionally the barrels are placed in the attic where they get nice and hot during the summer days and cool off during the night). The slower the maturation proceeds, the better the wine gets.
When the winemaker feels that the character of the wine is sufficiently formed, step by step the barrels will be moved to lower places until it is on the cool floor of the winery. Keeping the barrel constantly at high temperatures would be too costly, because of the evaporation of the wine - every year the winery loses about 1.5 - 4% of wine by evaporation, the so-called angels share. This slow aging system called ‘Canteira’ is the basis of all quality wines. Canteira is the name of the wooden beams on which the casks rests.
They also use a unique solera process, which resembles the sherry system, but not the same. In the Madeira solera system the wine stays for decades in wooden casks. Occasionally some wine is taken off and sold, up to 10%. The vessel is then refilled with new wine. This gives a wonderful blend of flavours: the old wines provide intensity and complexity; the young wines give vibrant freshness. After 10 times draining and refilling the entire cask must be bottled at once.
These wines attain amazing longevity and it is rare but not that unusual to find centenarian bottles or even older. These older wines have a wonderful combo of sweetness, acidity and texture with a delicious caramel, molasses and green apple flavours that seem to last forever on the palate. All 3 year old Madeira wine is produced in estufajes. The caramel-like character from this young Madeira makes it very suitable as an aperitif, also used in the kitchen for soup, sauces and stews, being today’s most exported style of Madeira wine.