Polyphenols

Polyphenols are the substances responsible for the colour of the grapes and therefore for the wines.

Green grapes only produce yellow polyphenols called tannins, but purple grapes also produce red polyphenols, called anthocyanins.

In time the yellow polyphenols intensify in colour and the red ones begin to disappear. A very old Rioja red owes its reddish colour to the yellow elements because of an interesting effect. This can be demonstrated with yellow cellophane paper. Looking through only one paper things are seen as yellow, but if one looks through five sheets the tone becomes reddish and with ten everything is seen as red.

Polyphenols do not only affect colour but also taste. Tannins are normally astringent. However, tannins have been noted to inter-react, joining together and losing their astringency. This happens with ageing and we have studied the oak'influence depending on whether it is American, French, old or new. The very interesting results obtained are expressed technically as polymerisation or in common language, like a smooth taste.

Here we show the results obtained from one wine in different casks during the same period of time:

Oak	Alcohol	Taste
New American	12,3	Very smooth
Old American	12,35	Slightly harsh
New French	12,4	Smooth
Old French	12,4	Slightly harsh

These results are very interesting in that they demonstrate that new oak makes the wine smoother than old. It is true that new oak can transfer harsh elements to the wine but this is compensated by its facilitating polymerisation (smoothing) of the tannins in the wine. This happens in casks which are less than five years old.

The reaction between wine and cask is complex in its effect on the maturing of the wine, not because matter is transferred from the oak but because this activates processes in the elements in the grape which tend towards a smooth and stable wine. This is very evident in the Rioja and in Tempranillo wines.

The fining of Rioja wines

Since ancient times, men have felt the need to give lustre to wines, not only because this makes them more pleasing to look at but because a wine with lustre offers more subtle aromas and a finer taste.

To do this, man has resorted since antiquity to products which have the characteristics of albumen - namely, that flocculate with the alcohol, acidity and tannins in wines.

Man discovered the clarifying or fining properties of animal blood, egg white and milk. At present these means of clarification are still used, as well as others which have come to light.

The use of fresh calf'or lamb'blood is no longer authorised. But dried blood albumen is marketed and, when dissolved in water, can be used to clarify wines..

Egg albumen is still used as it has been for centuries. For every hundred litres of wine the whites of two eggs are used, whisked with a soup-spoon of common salt and added to the wine.

Milk is no longer used as such but its albumen (casein) is marketed in powder form for the fining of wines.

Each one of these clarificants performs in a specific medium:

For white wines....................................	casein
For red wines.......................................	egg white
For rosé wines......................................	blood albumen

After these, other clarificants appeared, such as marrowbone jelly which is marketed in powder form and applied in the proportion of eight grammes per hundred litres of red wines.

In recent years very efficient mineral clarificants have begun to be used. One of these is a clay discovered in Fort Benton, U.S.A., appropriately named bentonite. In water, this clay forms a pasty mass similar to flour paste which flocculates with the wine and clarifies it.

More recently excellent results have been achieved in white wines by a combination of jelly and silicon dioxide.

Mineral clarificants are not new in the fining of wines. For centuries, products from deposits have been used, as is the case of the earth of Lebrija and Pozaldez.

Fining wine is carried out by adding the clarificant and stirring the wine to achieve a good mix. Two hours later, the clarificant will have flocculated, trapping the particles in suspension. For the next two days the floccules "get fat" before they finally precipitate. After ten days the clarificant with the trapped particles lies at the bottom of the vat/cask. However, it is necessary to wait a further four or five days for the sediment to settle completely so that the least amount wine is lost when this sediment is separated and removed. To do this, the clean wine is racked carefully.

In the Rioja, young red wines have traditionally been fined with jelly. Years later, in the same cask, two egg whites are used for each hectolitre and the clean wine is bottled by separating it in the same cask through the use of a stopper (a "falsete") situated above the bottom of the cask.

Glossary

Polyphenols. Elements found in the grape responsible for the red and yellow colours in the wine.

AnthocyaninsRed polyphenols. Only in red and rosé wines.

Tannins.Yellow polyphenols. They exist in white, red and rosé wines. They make the wine astringent.

C.I.Colour index. Relative value of the colour of a wine.

Potassium.Main natural metal component in wine, originating in the soil.

Tartaric.Main acid found in the grape which transfers to the wine.

Malic. Green grape acid which transfers to the wine. It is destroyed by the second fermentation, the wines becoming smoother.

pH. Measure of acidity in wines related to acid taste. It is an inverse measure. The greater the number the less acid the wine. For example, 3.0 pH is a very acid wine, 3.5 pH is a normal wine and 4.0 pH is a very dull wine.