True Spanish Sherry is the product of one particular variety of grape grown on a very special kind of soil in an intensely hot climate, fermented by an indigenous group of yeast species, and oxidized, blended, aged and fortified in an involved technique. All these factors, together, shape the nature of a true Sherry. No one outside the recognized Sherry region close to Jerez in southwestern Spain has been able to produce an identical product. Even the wines of Montilla, which is only about forty miles to the north-east are recognizably different, and may not be sold as Sherry.
Winemakers of many lands have long sought to imitate Sherry. They have produced some wines which come close enough to be attractive to a large market. This is about what the average home winemakers can do.
If you wish to make your own "sherry" it helps to start with some knowledge of how the original product is made. All true Sherry is made from the Palomino grape, a very neutral white variety. The hillsides around Jerez look like the sides of a Pinto pony, with big rounded patches of white soil standing out sharply in an otherwise red-brown landscape. The white soil is called "albariza", and the brown soil is called "barro". All of the Palomino grapes for Sherry are required to be grown on the white soil, which is chalky. Other grapes, one of which we are familiar with Pedro Ximenez, are grown on the brown "barro".
At harvest, in late September, the grapes are relatively high in sugar and low in acid, having been subjected to an intensely hot summer. Tartaric acid (or formerly "yeso", a crude calcium sulphate), must often be added to adjust the acidity, and SO2 may be added.
Fermentation is allowed to proceed without temperature control. Given the warm climate the fermenting juice must approach 25°C to 27°C, or about a maximum for survival of the yeast. Pure yeast cultures are not added. Fermentation is carried out by a mix of several yeast species carried naturally on the grapes. It is considered that these yeasts probably act sequentially, and each contributes to the ultimate character of the wine. Fermentation is carried out in Sherry butts of about 500 liters capacity or in moderate-sized tanks. Butts are filled only about 3/4 full.
On completion of fermentation the wine, if in butts, is left on its lees in its original butt. Within a week or so some of these begin to develop a surface skin of flor yeast. The flor yeast is not an organism which happens to find its way into the young wine, or was placed there by the winery, it is one of the yeasts carried in on the grapes. Unlike most other yeasts it grows as a surface "skin" on developing wines that are exposed to air, and which have reached an alcohol content of 14.5% to 15.5%.
At about this time each butt of new wine is examined in order to ascertain in what style it is developing. Those showing strong growth of flor are marked as destined to be fino sherries, and perhaps eventually amontillados.
Those without flor are marked as destined to become something in the "oloroso" family of sherries. The style into which each butt chose to develop was formerly quite unpredictable. Today the sherry makers are beginning to learn how to guide each butt towards a chosen style.
Wines that have developed a flor, and are destined to become finos, are left without fortification at this stage. Wines without flor, and destined to be olorosos, are fortified now to about 20% alcohol, this ensuring that they will not subsequently develop a flor.
From this point each butt moves into the first stage of the "solera" system, the "criadera" or nursery, in which it will stay until it has proven its direction of development. Each winery, or "bodega" has quite a number of soleras, each aiming to turn out a particular style of sherry that will remain very constant from year to year.
A solera is a large group of butts of sherry of eight or ten or more vintages. It is organized and managed so that the oldest, and last, butts produce a complex blend that derives from every younger butt. In each year from 5% to 30% of the wine from the oldest butts is removed to be prepared for sale. Each of those oldest butts is then refreshed with wine from all of the next oldest butts. This process of refreshment is continued back to the youngest wine in the solera.
Sherry from a solera is virtually never sold as it is, but is made up into blends with sherry from other soleras. The aim is that a blend which has proven to be popular in the market place may be reproduced very accurately in each year, regardless of the year-to-year differences along the way.
All sherry is made fully dry, but some of it is sweetened for export to the "sweet-tooth" countries. Most sweetening is done with boiled-down juice of the Pedro Ximenez grape. The caramelization of the sugar as the juice is boiled provides the nutty brown colours we associate with the sweet olorosos .
This very brief account of the production of Sherries should serve to illustrate how difficult it is for a home winemaker to truly imitate this style of wine.
It is probably true to say that the quality of a home-made product will depend upon how far you are able or willing to go to duplicate the making of the real thing.
The great majority of home-made "sherries" are accidentally oxidized white wines that have been sweetened and fortified. Some have been baked a few months in "estufas", heated chambers that duplicate the process used to make Madeira. This heating also duplicates the natural high temperatures to which the wine is subjected in Spain. Wines made by such processes are seldom really attractive, and they certainly don't taste like Sherry.
At the other extreme, we have a few winemakers in the Pacific Northwest who have gone to a great deal of trouble to produce "sherries" in a manner that duplicates the Spanish techniques quite closely. Some of these winemakers even have their own "mini-soleras" in small oak cooperage.
The wines we have tasted from these facilities are excellent. It would take someone knowledgeable to tell them from true Sherry.
Following are a few suggestions:
Choice of grape: Use a neutral grape, such as Palomino, Thompson Seedless, or French Colombard. A grape with a pronounced fruity flavour will not make the true Sherry style. You can observe this in some of the Australian and New Zealand "sherries" where fruity varieties such as Madeline Angevine have been used. The grapes should be fully ripe, with a juice s.g. around 1.100, and not too high in acid. 0.7% or 0.8% is ok.
Fermentation: Use a sherry yeast. Ferment the juice normally, but at a warm temperature of 20°C or a little above. Place the carboy where it will not be disturbed at all. If you are to make an oloroso style, then fortify to 20%.
Fortification: Calculate alcohol additions by using the "Pearson Square", also termed the "St Andrew's Cross".
Normally, sherries, ports, madeiras and similar wines are fortified with brandy to an alcohol value between 18% and 22% vol/vol.
In this example the spirit being used is brandy at its usual strength of 40%.
To use this diagram, the % alcohol in the wine is deducted from the % alcohol desired, and the difference written in the lower right corner. Similarly the difference between the % alcohol in the spirit and the % alcohol desired is written in the lower left corner. From this we find that we must add 20 volumes of the wine to 8 volumes of the spirit to correctly make our fortification.
Oak: Oak furnishes another important component of the sherry flavour. If you have suitable small oak casks then the wine can be moved to them after six months to a year in the carboy. Again, do not seal the bung, but simply cover the hole with a wisp of cotton wool to admit air but exclude fruit flies. Check the wine frequently, because it will pick up oakiness rapidly in small cooperage.
Oak chips are not as satisfactory, but still may be considered. The oak surface presented to the wine when using chips is vastly greater than the interior surface of a small cask, even if only a few ounces of chips are used. Monitor the taste of the wine daily until the desired oakiness is attained.
Aging: Any true Sherry we purchase has been aged at least about 8 years by the time it makes its way through the solera system. Our imitations must also be aged if they are to have anything like the smoothness and maturity of a true Sherry.
Sulphite: Don't use sulphite in wines destined to be sherries . Sulphite will very likely prevent the oxidation and formation of aldehydes that is essential to creating the sherry flavour and aroma.
Manzanilla: Similar to fino, but lighter. Made at Sanlucar de Barrameda near Jerez. Very dry.
Fino: Pale and dry. Much used as an aperitif, or with "tapas" (snacks) in late afternoon.
Amontillado: An aged fino, softer, darker, and sometimes off dry. A favourite with soups.
Palo Cortado: Intermediate between a fino and an oloroso. "Dry Sack" is an example. Dry to medium.
Oloroso: Available dry, but usually sweet. "Nutty Solera" is an example. Very sweet olorosos are sometimes termed "Amorosos".