Sherry wine

Sherry Wine Ageing

Olga Nikandrova and Denis Shumakov.

Sherry ageing can be biological, oxidative or mixed-type. In biological ageing, the main “working agent” is sherry yeasts, which form a film on the wine’s surface (or flor). In oxidative ageing, the main transformation happens with the wine in its interaction with oxygen and barrel wood. In mixed-type ageing, sherries undergo first biological and then oxidative ageing.

Regardless of the type ageing may be done either statically or dynamically.

Static ageing

When matured statically (this type of ageing is called Añada), the wine of a certain vintage is not blended with wine of other years. This ageing type helps preserve the character of a specific harvest, but since no special accent is made on millésimes in the Jerez region, the static ageing is done rather rarely — for specialty, signature, jubilee and gift wine production. It is worth mentioning though that static ageing is not static in the strict sense of the word and it does provide for the movement of wine. During the ageing the wine evaporates and the quality of the sherry undergoing static ageing diminishes, so it is transferred from barrel to barrel and from time to time either the quantity of barrels of one millésime or their size diminishes.

Dynamic ageing (Criaderas and Solera)

Dynamic ageing is the most known characteristic of sherries and their most glorified special feature. In the first approximation this technology is very sightly, easy to comprehend, convincing, and nicely named: the Criaderas y Solera or Criadera y Solera system. It is difficult to give an accurate and sweet-sounding translation of this term, and if translated not that accurately and beautifully it sounds something like the Nursery and Basis. So, let it simply be Criaderas and Solera. Or Solera and Criaderas. Or Solera and Criadera. Or Solera system.

Criaderas and Solera are the names for the groups of barrels where sherry is aged successively. Solera is the name for the group of barrels from which the wine is bottled. Criaderas are the other groups of barrels, and sherry is transferred through them during the process of ageing. And the process of ageing itself is organized the following way.

Several times a year, a portion of wine is taken from the solera for bottling (no more than one third). After this the solera is replenished with wine from the first criadera. The first criadera is replenished with wine from the second criadera. The second — from the third. And so on to the last criadera, which is replenished with young wine kept in separate containers till then. The quantity of criaderas may be different — from three up to fifteen, for instance. Explanatory diagrams almost always show the Criaderas and Solera system as rows of barrels mounted on each other in a strict order, the first row being solera and the others — criaderas (the first criadera — the second row from the bottom, the second criadera — the third row, and so on). In reality, barrels are stored mounted on each other’s side, but the strict order of “solera at the bottom, then criaderas in series, one on top of the other” is rarely observed, and respectively marked barrels can be installed in different places.

Through constant and gradual transfusion of sherry between criaderas as well as constant addition of young wine dynamic ageing levels the natural difference between vintages thus providing for the consistent quality of the final product. However, uniformity of quality is but one of the outcomes of such ageing and there are more, often worthier, reasons for the use of the Criaderas and Solera system.

At this point we need to get back to the sherry ageing types: biological and oxidative (we’ll ignore the mixed type for a while, as it is a derivative of the first two types).

Biological Ageing (under flor)

For sherries undergoing biological ageing (Fino, Manzanilla, Amontillado, Palo Cortado) the use of the Criaderas and Solera system is a technical necessity. Sherry yeasts that form flor are voracious and omnivorous — they consume residual sugars, ethanol, glycerin, and other components of the wine and require regular refreshment of the nutriculture medium, that is they need the inflow of young wine.

Sherry yeasts which constitute the veil of flor (sp. “flower”) is a variety of wine yeasts capable of active life at a relatively high alcohol content in wine. By this time there are four identified types of sherry yeasts: Sacharomices cheresiensis, Sacharomices rouxii, Sacharomices montuliensis and Sacharomices beticus (these names are applied in the Jerez Region but they may differ from the names used in toxicological directories). Normally Sacharomices beticus yeasts dominate in flor, they may comprise more than 75% — but the exact yeast composition of flor depends on many factors, i.g. on the bodega’s microclimate or the criadera’s serial number (the closer the criadera is to the solera, the more Sacharomices montuliensis there is in flor). The composition of flor significantly affects the taste and aroma of the wine and is unique for every single barrel.

The ageing under the veil of flor results in the appearance of several interesting and enjoyable characteristics of sherries.

First, Fino and Manzanilla do not grow darker, having spent many years in barrels. There simply no spare oxygen for oxidation, which is the main cause of the wine darkening (it seems to be called enzymatic browning).

Second, during the ageing under the veil of flor the content of alcohol in the sherry reduces, as it is also consumed by flor. In a 600-liter barrel filled with 500 liters of sherry flor “drinks up” about 6 liters of alcohol per year. And if new wine is not added, flor may die.

Third, flor actively processes glycerol — during the years of ageing its content in sherry decreases several times and becomes less than two grams per liter (for comparison — glycerol content in dry white wine is usually a bit more than twenty grams per liter). Such a low glycerol content most directly affects the taste of sherry — already dry wine (having hardly any sugar) becomes incredibly dry, and there appear all those notes which largely define Fino’s and Manzanilla’s character — freshness, harmoniousness, minerality. Besides glycerol content flor affects other components of the wine, attaching enjoyable yeasty notes and fabulous lightness to its flavor.

Forth, flor lives for some time, but then dies. Dead yeasts fall to the bottom of the barrel creating a layer of sediment which partially dissolves in the wine, saturating it with vitamins, amino acids, proteins, enzymes, and all sorts of other useful components. Which is good and important.

Flor is formed on the surface of wine during its racking after fermentation. The fortification of sherry for biological ageing up to 15,5° prevents unwanted growth of other yeasts but lets flor fully develop.

For the normal life of flor the wine should be low in sugar, its alcohol content shouldn’t exceed 16%, the barrel itself should not be filled to the top — so that the yeasts had air and space to grow. The temperature in the room where sherry is aged should be about 18°C, humidity — no less than 65% (so that water in wine did not evaporate and alcohol concentration did not rise to a dangerous level for flor). If necessary, the floor of the bodega may sprinkled with water to cool the room and raise humidity. Besides, it is customary to set barrels with sherry aged under the veil of flor in the lowest rows (the first and second from the floor) — as it is cooler there.

When everything goes right, flor forms a layer of 1 to 3 cm width on the surface of sherry.

So, once again, ageing under flor in the Criaderas and Solera system is a technological necessity for Fino and Manzanilla — otherwise ensuring a constant supply of fresh wine for normal functioning of sherry yeast would be very difficult.

Oxidative Ageing

For sherries undergoing oxidative ageing (without flor; it is used for the production of Oloroso, Pedro Ximénez, Moscatel and for final stages of the production of Amontillado and Palo Cortado sherry) the use of the Criaderas and Solera system is not critical. It is just as well possible to receive very good result using static ageing for them — however in most cases dynamic ageing is still used. The matter is that even regardless of flor the ageing in the Criaderas and Solera system has a number of substancial and technological advantages.

First of all, it is simply convenient as it allows (due to the continuous blending of old wine with younger one) to produce even-quality high-grade sherry in controlled volumes almost regardless of the quality and quantity of raw material (which differs from year to year depending on the weather, for example). Second, continuous refreshment of the wine intensifies oxidation process occurring in it and accelerates its maturation. Besides, there’s one more nuance in the use of the dynamic ageing scheme; it is more of a historic than actual nature.

In relatively recent past, one of the key indicators of the product’s quality was its ability to withstand long-term storage and to be safely transported. Mature sherry of long oxidative ageing is more stable and is better suited for storage. Any process that accelerates the maturation of wine without a major increase in its cost is commercially justified. So, in the past, dynamic ageing was a profitable innovative technology.

Nuances of Ageing

A few more important accents associated with ageing. Amusing facts, so to say.

A “wall” of barrels mounted on top of one another so that every barrel oа the next row is placed in in the “recess” between two barrels of the previous row is called Andana. Usually andana consists of 3-4 rows, it may be dangerous to make it higher as the pressure on the lowest barrels becomes too heavy. Since the two lowest rows are often occupied by sherries of biological ageing, there may be barrels with very different types of sherry in one andana. Special marking system is used not to confuse barrels.

Barrels for sherry ageing are made of American oak (it breathes better), and they are previously saturated with wine. It is believed that the older barrel, the better it suits sherry ageing. Twenty-year-old barrels are considered young, and fifty years being the optimal age. The state of barrels is closely monitored, worn out barrels are repaired. The volume of barrels used for ageing sherry — 600 liters. They are normally filled with 500 liters of wine.

Blending sherry during its ageing on the dynamic scheme is not mindless pouring and mixing everything together. Every barrel has its individual character and the aim of a bodega’s specialists is to figure out this character, preserve it and intelligently fit it into the composite character of the bodega. In fact, blending sherry is a complex elaboration of a drink with if not specified then at least with desired characteristics.

Sometimes, when evaluating the contents of barrels, cellar masters rate some of them as outstanding, mark them with the word No and exclude from the process of dynamic ageing. Such barrels are normally left for the owners of the bodega, specialists, and some very lucky persons to enjoy. A special status also may have a barrel closest to the aisle in the lowest row of andana. It is called Bota Punta. It is always the easiest barrel to get to and the most convenient to sample wine from. That’s why it needs more wine to be added which is done not only from the first criadera but often from other barrels of the solera. So, in the end, the wine in it may be on average longer aged, more concentrated and expressive than in other barrels of the solera. It may also happen that the cellar master would taste sherry from Bota Punta and decide to write No on it.

Careful transfusion of wine is very important during biological ageing of sherry on the Criaderas and Solera scheme. It is required not to damage flor or stir up sediments.

When sherry is ageing biologically, the content of alcohol in it is constantly decreasing — through the consumption of ethanol by sherry yeasts. On the contrary, during oxidative ageing, the content of alcohol in sherry is constantly increasing — through the evaporation of water from sherry.

According to the rules of the Regulatory Council sherry is to spend at least two years in barrels. Since it is impossible to say the exact time of ageing and maturation of any specific sherry which was aged dynamically, the time of ageing is determined by dividing the total amount of this specific sherry aged in criaderas and solera into the amount of this sherry to be bottle during one year. This means that a bodega should have in store at least two times the amount of sherry it is planning to bottle in one year.

If sherry is aged biologically, the frequency with which part of it can be taken for bottling depends on the intensity of the work of flor. Which, in its turn, depend on the climate. Thus, for example, in Jerez de la Frontera, where they produce Fino, sherry is taken from the solera 3-4 times a year — flor normally has a “winter break” there, kind of hibernating. In Sanlúcar de Barrameda, where climate is milder, where flor works all year round, and where they produce Manzanilla, sherry may be taken from the solera 8-9 times a year, sometimes even more. The number of criaderas is also associated with the activity of flor — they have 3-7 of them in Jerez, and up to 15 — in Sanlúcar.

And, finally, the last one. The dynamic scheme of ageing (in Criaderas and Solera system) is by right considered traditional for the Jerez Region. Nevertheless it is used not only in the Jerez Region, and not solely for ageing sherry. Besides it is worth mentioning that the static scheme of ageing Añada (when wine of different vintages is not mixed together) was used in the Jerez Region prior to the dynamic one. The system of Criaderas and Solera was introduced most probably at the end of the 18^th century.

Read next — Sherry Filtration

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