Fortification of Sherry

What is fortification? In the case of Sherry, it is simply the addition of small amounts of alcohol to a fermented wine in the case of the dry wines and to partially fermented wine in the case of PX and Moscatel. The Spanish word for fortification is "encabezado".

Why is Sherry fortified? Sherry has been a fortified wine, at least for export purposes, since the Middle Ages. The Moors introduced the art of distillation sometime before 900 AD and it was found that adding a little alcohol to the wine gave it better stability. There are two reasons for fortification: firstly it was an effective technique employed to ensure the arrival in sound condition of wine subjected to long sea journeys to the export markets. In the days when Sherry was shipped in butt on sailing ships, bacterial spoilage, acetification and oxidation were serious risks. Wines were sometimes dispatched while still fermenting in an attempt to prevent this. The second reason, and why it is done today, is that by varying the amount, and the timing, of added alcohol, different styles of wine can be produced efficiently and predictably.

Does it need to be fortified? While it is possible to produce unfortified Sherry – and there are now one or two with the DO - it is more difficult and hit-and-miss. Flor is happy at lower strengths but requires great care to manage its stability. In the old days the grapes were often harvested later and/or sunned for a few days to raise their sugar – and therefore alcohol – content, but that can give the wine a slightly richer more glyceric character than may be desired. It is generally agreed that a strength of about 15ᴼ is required to combat undesired microflora while still allowing the desired microflora to do their work.  EU rules covering "Vinos Generosos" require a minimum of 15ᴼ and that the wine is fortified, but on 1 February 2017 the Consejo Regulador asked Europe for a relaxation of the need to fortify in the case of Finos and Manzanillas which reach 15% naturally. Many modern oenologists prefer the flexibility and precision offered by careful use of fortification. In this commercial world there is unfortunately little room for the often sporadic nature of Sherry’s development. There is no longer time to wait until a Fino decides to become an Amontillado by itself; it is simply re-fortified to over 17ᴼ to kill off the flor and start the oxidation process. The same happens with Palo Cortado but earlier.

When is it fortified? Vino Generoso, or dry Sherry, is fortified after the wine has been classified as to whether it will age biologically or oxidatively. The former will be fortified till its total alcohol content reaches 15-15.5ᴼ (Fino and Manzanilla) and the latter, Oloroso, to 17ᴼ. With its higher strength the Oloroso will not change and is ready to go to the criaderas when required. At a lower strength, the Fino and Manzanilla might well change, and they are kept back for 6-12 months in sobretablas. When they are re-classified, any wines which have developed fuller characteristics yet retain some elegance and perhaps even a little flor will be re-fortified to 17ᴼ and marked as Palo Cortado and will continue ageing oxidatively. Any which are less elegant and lack a viable amount of flor will also be fortified to 17-18ᴼ and become Oloroso. In the case of PX and Moscatel, they are usually allowed to ferment a little before fortification, so less spirit will be needed.

What kind of alcohol is used? In the past most bodegas distilled some brandy, generally for personal use, but when Jerez Brandy took off in the late XIX century it soon became apparent that the vineyards of the Marco de Jerez could not supply nearly enough grapes to produce the volumes required, so distilleries were built in Tomelloso, La Mancha, where there was a plentiful supply of suitable grapes.  Wines for the best brandy were distilled in pot stills producing "holandas", but using column stills, the wine could be distilled to 95ᴼ stripping any flavour and producing what was effectively neutral spirit or "aguardiente" which would not change the Sherry’s flavour profile. All spirit must originate from grapes, but those grapes are normally the Airen of La Mancha. This tiny addition of spirit which is not from Jerez is allowed by the Consejo, but there are moves to produce that spirit locally so that Sherry is 100% Jerez. Grupo Estévez send Palomino from Jerez to La Mancha for distillation.

How is the alcohol added? The method employed is known as “miteado” or “mitad y mitad” (half and half). Adding such strong spirit to young wine upsets its constitution and would surely damage any flor, so some similar but as yet unfortified mosto is mixed with a measured quantity of spirit and then added to the young wine. Even using this method the wine is out of sorts for a few months, tasting rather dumb, but it does recover. This is one reason that the wine must have a minimum average age of two years before sale.

How much alcohol is added? Not a great deal. The rule of thumb is 5-6 litres per degree. After normal alcoholic fermentation Sherry wine will, depending on vintage, harvest dates and vineyard location, contain between 11.0ᴼ and 12.5ᴼ. So as an example a butt containing 500 litres of wine at 12ᴼ will require about 18 litres of spirit to be added to bring it up to 15ᴼ, while a butt with 500 litres of Oloroso at 12ᴼ will need around 38 litres of spirit to raise it to 18ᴼ. There are other factors to take into account, however. For example, flor yeast consumes alcohol, so it is possible that a Manzanilla, say, could lose up to 1½ᴼ, leaving the solera wine as low as 14ᴼ and may need further fortification before bottling simply to comply with the regulations. In the past Finos and Manzanillas for export tended to be fortified to about 17 or 18%, but with better stabilisation and faster transport facilities that is no longer necessary and the wines are correspondingly more elegant. Oxidatively aged wines, on the other hand, can gain up to 5ᴼ alcohol as water content is lost through transpiration and there is no flor involved. Actual quantities lost or gained naturally depend on the ageing period and the microclimate of the individual bodega. It should be remembered that under EU law alcohol statements on labels are allowed a tolerance of  +/- 0.5% by volume, however Finos and Manzanillas must have at least 15% at bottling.