Second year evolution

Throughout its second year Rioja wine is kept in oak casks with a capacity of 225 litres.

The changes undergone by the wine are, to a large extent, dictated by the nature of the oak.

These changes can be expressed as:

Crystalline transformations.

Transformations in colour.

Changes caused by racking.

Chemical changes.

As in the wine's first year of life, during the second the phenomenon of crystal formation continues, as does their precipitation to the bottom of the cask. In the second year the precipitation is fundamentally due to lime tartrate. The intensity of the process mainly coincides with cold periods, occurring therefore during the second winter.

In theory, specialists used to think that two winters would be sufficient for the spontaneous stabilizing of the wine. During the first, the potassium bitartrate precipitates and in the second the calcium tartrate. Thus a wine aged some twenty months would be ready for bottling. But the real situation is different and there are wines which can precipitate some tartrate crystals even in their fourth winter. This risky phenomenon occurs especially when, during the summer, the wine is kept in vessels lined with "alumbres". In this case the wine loses tartrate in winter only to take it back from the walls in the summer heat.

The transformations in the colour of the wine are profound. Wine in casks undergoes extreme changes, especially in the second year.

The colour of red wines is due to two fundamental elements:

• Red-coloured elements or anthocyanins.
• Yellow-coloured elements or tannins.

New wine is very rich in anthocyanins or red colour. After a year up to 50% is lost, and afterwards some is regained.

In cask the red colour fades and the yellow is intensified, mainly because of tannin filtering from the oak.

We can fix at 100, as a relative unit, the intensity of colour in a new wine. At the end of the first year the figure falls to 35%, rising to 45% by the end of the second year. This rise is due to absortion of tannin from the oak.

At the beginning of the second year the red elements can be 0.2 g/l., falling to 0.07 g/l. by the end of that year.

In contrast, the tannins or yellow elements are at 1.5 g/l. at the beginning of the second year, reaching approximately 1.7 g/l. at the end of the year if there is intense use of wood, or 2 g/l. if the wood is new.

So in cask the wine passes from clear red to ruby red as well as assimilating elements from the oak.

During its time in cask the wine clears itself spontaneously and inactive solid matter (plant residue, bacteria and dead yeast) settles at the bottom, leaving the wine clean and occasionally bright. If the wine were not separated from these elements it would eventually become cloudy again. For this reason the wine is racked off every three or four months and poured into clean, dried casks. However, not all the wine is drawn off, a small amount being left at the bottom. This is the sedimentary matter which makes cloudy wine and is logically rejected for use in quality wine. Each time the wine is drawn off several litres of sediment are separated.

n the racking process the wine receives a certain amount of air in its passage from one container to another, sustaining the liveliness of the red colour of the anthocyanins.

There is, however, another reason why wine can only stay in one container for less than six months. Oak is a material with only slight permeability. It eventually becomes soaked in wine, some of which evaporates through the pores, at the same time permitting the entrance of air. In consequence the wine loses volume, even in a closed cask, and a pocket of air is formed which could later oxidise the wine. Periodic drawing off of the wine avoids a dangerous increase in the volume of this air pocket.

There also exists two interesting types of chemical processes:

• Esterifications
• Oxidations

Esterification is the very slow combination of wine acids with alcohol. Basically these are tartaric acid, lactic acid, succinic acid, etc. with alcohol (ethanol). After some time in cask they react in very small proportions and produce compounds like ethyl tartrate, ethyl lactate etc. One can occasionally notice a certain "cheesy" aroma in some old Rioja wine. It is caused by the formation of ethyl lactate. The quantities are very small but the aromas produced are rather distinctive.

Oxidation in the cask is due to the very slow diffusion of air through the oak, producing a limited amount of oxidation, mainly of the alcohol which turns into aldehyde. This has a special aroma (these are the elements which are thought to produce the aroma of Sherry and Montilla wines). This kind of oxidation in Rioja wine is very slow throughout the time spent in casks.