Diseases in Rioja wines

When considering alterations or diseases in wine from the Rioja, one has to bear in mind that by nature it is a product which is hostile to air, capable of taking this hostility to harmful extremes. Technically speaking it can become so reductive that it can spoil for this same reason.

There are certain broad chemical alterations and others which are microbiological. However, the typical deterioration in all wines by iron scarcely occurs in the Rioja. Nor does the classical microbial deterioration which causes souring. The deterioration of Rioja wine is more subtle and occasionally undefinable, but never coarse, which is necessarily the case bearing in mind that it is classified as a fine wine. This is due to the use of Tempranillo grapes, giving the wine very stable colour and lustre.

With healthy grapes there may appear, in some traditional processes, a taste of "sulphide". It is an unpleasant smell, but a consequent of a scientifically perfect fermentation. It is easily corrected by means of racking, and thus airing. It only occurs in young wines.

If the grapes deteriorate because of rain at the time of harvesting, certain moulds will develop which after fermentation could make the colour of the wine unstable, tending towards a brown colour. It is called "oxidasic failure". It is corrected quite simply by means of fining. However, these wines will not go on to being Reservas.

When young wines of an age of less than two winters are bottled, there may occur in the bottle a slight precipitation of granules similar to sugar, sometimes fused. These are bitartrates. They have no negative effect at all on the quality of the wine except for their appearance in bottle and merely denote the youth of the wine.

Once the wine is bottled it must be corked. This brief contact with the air temporarily changes the quality of its taste and aroma, the wine becoming insipid. After three months, the wine assimilates this brief contact with the air and offers all its splendour to the winetaster.

After years in bottle, because of slight oxidation through the cork, wine may offer a diminished resistance to air and lose its qualities of aroma and taste. It is said to have arrived at its "optimum" and to be "past its best".

These alterations are not caused by microbes.

The micro-organisms which live in the winemaking environment are moulds, bacteria and yeasts. In over five degrees of alcohol the moulds die. They do not survive in Rioja wines. What can happen is that through improper cleaning, wine residue can be found in a pipe or vat. This may lose its alcohol and grow moulds. If new wine is then poured into this container it will "kill" the mould but acquire its bad taste, something the people from the Rioja call "cano" ("white-hair") because of the original white colouring.

Yeasts carry out fermentation and then disappear from the wine after the sugar has been transformed to alcohol. In white and rosé wines, yeasts may remain for some time. If the wine is not well clarified before bottling, they could cause sediment in the bottle after a certain period of time. This yeast does not alter the wine itself but affects the lustre. If the effect on the lustre is strong the aroma and taste are spoilt.

Bacteria are the most frequent alterations of microbial origin.

In fermentation above 35· C the yeasts die and bacteria grows forming bittersweet or bitter tastes from the grape sugar. It is called the "manita" or mannitol disease.

In young rosé and white wines made from coarse-grained grapes such as the prohibited variety, Calagraño, due to a lack of substances in the skin, certain bacteria from "fibrous growth" appear making the wine sticky and syrupy. This alteration has an alarming appearance but is very easy to correct.

Red wines, after a long time in bottle, may suffer from a bacterial disease called "vuelta" ("tourne"), frequent in many wines. It is known by the French as "tourne" and by the Italians as "girato". It is a slight alteration which leaves a light sediment in the bottle and generally, though this may seem paradoxical, improves the wine, increasing its bouquet.

In the wine cellar one sometimes sees at the top of the vats/casks a white layer which the winemaker call "natas" ("skin") or "velos" ("veil"). These are yeasts that live in young wines which are not hermetically sealed. They are not of pleasant appearance but their effect on the quality of the wine, if they are not allowed to live, is very small.

All the microbes that cause alterations in wines are innocuous to man. Enologists occasionally, by way of experiment and for a better diagnostic, taste diseased wines without fear; they know that the microbes one might consume in a diseased wine will cause no harm.