"Classical" vatting

At the end of the 18th Century, the inhabitants of the Rioja asked themselves what possibilities there were for exporting their wines. They realised that their wines often suffered from a taste given by the stem. To avoid this, they decided to vat the grapes without stems. The person responsible for this was called Quintano. He lived in Labastida, and applied the Bordeaux methods. We call this the "classical" system, imported from Bordeaux and consisting of vatting the grapes without stems. Although this system is not originally from the Rioja it is the system which, for centuries, has given our wines the great prestige which they enjoy today.

When the harvested grapes arrive at the bodega, they are dropped into a de-stemming machine. Depending on the wishes of the enologist, he can separate the stem only, respecting the structure of the grape, although it becomes somewhat injured. Or, he can operate more violently, remove the stem and crush the grape completely.

The grapes, now without stems, are pumped into the fermentation vats. These usually have a capacity of 25,000 litres and are filled with only 20,000 litres.

They are cone-shaped oak vats, or cement or stainless-steel containers. The grapes, when pumped into the vat, are a homogeneous mass of skin and liquid. After 24 hours, the skin concentrates in the upper part of the container and forms the "sombrero" or "hat". The liquid stays at the bottom. There are an estimated 4,000 litres of "sombrero" and 16,000 litres of liquid. When four days have passed, the yeast which at first adheres to the grapes, multiplies and ferments, i.e., converts the sugar into alcohol, raising the temperature by some 15· C. The presence of CO2 pushes the "sombrero" upwards. As of the tenth day, fermentation slows down and the "sombrero" sinks slowly into the liquid.

Destemmer-squeezer. Stem remover. Pump. Fermentation "cone" (external) "Cone" filled with recently harvested grapes. "Cone" six days after vatting. "Cone" with completely fermented grapes after 12 days.

Among the numerous phenomena associated with the fermentation of picked or pressed grapes the following are the most important:

1°. The formation of alcohol by the total transformation of the sugar in the fermentation vat.

2°. The transfer of the colour from the skins to the liquid. At the same time alcohol is produced and the heat from the fermentation is accumulated.

It is very interesting to observe that this would occur with the fermentation of the whole grape but there is a difference. When the pressed grape ferments, the acid pertaining to the greenness is not destroyed. The wines are richer in acidity.

The enologist must know the fermentation process within each vat once this commences. He must know the quality and if the process is normal or unusual. To do this he carries out three actions. The first of these is to apply CO2 moderately as an antiseptic guaranteeing the cleaning action of the yeasts: another two controlling actions by means of the assessment of density and temperature. Due to the sugar the grapes have a high density. When wine is made, as the sugar is transformed, their density decreases.

Water has a density of 1.000. Rioja must usually has 1.1 and Rioja wine 0.99. Density control, therefore, varies every day of fermentation from 1.1 to 0.99 and is carried out by using density gauges. The refractometer, which is very useful for measuring the richness of the musts, cannot be used after fermentation begins. The enologist, by means of a density gauge, also knows when fermentation stops. This could be dangerous if there is still some sugar to be transformed. Likewise, the temperature is controlled by means of simple "maximum" thermometers, tied to the end of a pole in order to insert them into the mass during fermentation. The danger of high temperature is great.

Let us remember that yeast lives at between 20 and 32· C. If fermentation accumulates heat up to 35· C, the yeast gives way to bacteria. The ideal temperature for the bacteria is 38· C. They may spoil the wines, making them taste vinegary. In order to monitor the evolution of the fermentation, the enologist loads data onto fermentation charts. They are prepared with densities and temperatures based on the number of days the grapes have been in the vats. By means of these charts, the enologist knows the specific values at each moment and their tendencies. Wines obtained by fermentation of the de-stemmed red grape are more acid than those attained by vatting whole grapes. In turn, those obtained from pressed grapes are usually still more acid.

In order to follow the evolution of this process, while the grapes are in the vats, the technician plots their density and temperature values on fermentation charts.

These charts not only inform us of the specific values recorded at a given time but also help the oenologist to identify trends.

The wine produced by the fermentation of de-stemmed red grapes is more acid than when whole grapes are used, although pressed grapes tend to have even more acidity.

Some characteristics of wine produced from the same grapes with different fermentation systems
	Wine from the fermentation of whole grapes			Wine from the fermentation of de-stemmed grapes
	"Lágrima"	"Corazón"	"Press"	"De-stemming"	"Crushing"
Alcohol content	11º	12º	12º	12º	12º
Tartaric acidity	4.2	3.8	3.6	4.5	4.7

While Rioja wine is fermenting, each litre of must released 105 grams of CO2 gas, equivalent to 54 litres.