Production of wine in Kvevri – History, description, analysis
from: Dr. David Chichua, Lecturer at the Telavi State University, Georgia (www.tesau.edu.ge)
The making of wine in Kvevri is the oldest known method of wine production. Approximately 5000 years ago, this method spread from the region around the Caucasus across the world. The oldest clay jugs, found in Georgia, are more than 7.000 years old and appear similar to the current Kvevri jugs. There are several archaeological finds within the Mediterranean area, which diversity in shape and size equates to their functional diversity in use of these clay jugs.
Clay jugs were almost the only alternative for wine fermentation, storage and transportation until the Roman conquest of Northern and Middle Europe. It was also common to use hoses of hide to transport the wine. Open pans made of trees or stone were used to ferment little amounts of wine. The usage of wooden barrels from Northern Europe gained more importance from the 1st century B.C. onwards and soon replaced the common clay material.
Naturally, this process is logically, but one can’t say for sure, if improving the quality of the wine played a key role in this process. Wooden barrels are easier to produce and to clean. There is also no danger, that they fracture during transportation or get damaged due to an earth quake and therefore the wine gets lost. It is also easier to discover little leaks and pretty straightforward to repair them.
The increasing importance of using wooden barrels in terms of the quality of the wine is not that easy to explain. The opinion, that oxidized wine from immemorial times neither had a smell nor a taste, can’t possibly be true. Only a neutral grape variety would have been selected. But if people already back then chose the grapes according to their fine scent, than it would have been possible for them to maintain this feature.
Chances are that fermentation of grape juice without any preliminary sedimentation in the barrel – how they used to do it around the middle Ages – was a horrible method according to the quality of the aroma of the wine. Fermentation at a constant and cool temperature in a Kvevri, which are carved into the ground, was a better method to maintain the aroma of the grapes than using wooden barrels. Changing viniculture from wooden barrels to Kvevris didn’t sample in parallel world-wide. Countries with warmer climate tend to stick longer to the older methods, as a result of their warmer climate, grapes used to have a higher acid content and therefore, a higher level of sugar and tannin. In Georgia, Kvevri were the only used wine tanks until the beginning of the 20th century.
Kvevri were produced only in a few villages from special clay and after being burned, they were lined in the inside with melted fat or bees wax. The same Kvevris were used for centuries and had an impact of the wine’s quality. Besides the quality of the Kvevri, the place where they are buried into the ground is of a similar importance.
In West Georgia, where grapes are grown on wet loamy soil and were used to being harvested in late autumn, Kvevris were burrowed into dry sand and were protected by a simple roof. However, In East Georgia, Kvevris were burrowed deep into the cellar, because the temperature is much higher there during the harvest.
The process of fermentation in Georgia varies from town to town depending also on the quality of the vintage. In general, it is possible to distinguish three stages:
- The pressing and fermentation followed by the agitation.
- The alcoholic fermentation in the Kvevri.
- The storage of wine on the lees.
Grapes were presses in so called “Sacnakheli”. Sacnakheli is a long tub made from a log (preferably linden) or made from a monolithic stone like clay or lime. There is a hole within the Sacnakheli, to drain off the wine. Before pressing, a “Chelti” was laid into the ground, followed by grass and on top the grapes. The grapes were treaded and the juice could flow through the “Chelti” into the Kvevri.
There a three different fractions of must. The first is mostly cloudy, the second is clearer and full-bodied and the third is rich of tannins and brown in color due to a strong oxidation. The grape juice is led into the Kvevri for fermentation. After pressing, the drained mash rests for a night in the Sacnakheli. Only the next morning, a third, a quarter or half of the mash – depending on the sort of grapes, their acid and sugar content – is added to the must. Quite often it happens that the mash of aromatic grapes is being mixed with that of less aromatic grapes. At a maximum of 5 % peels of the grapes are added to extremely acescent grape juice. Less acescent, early harvested grapes, like the ones in East Georgia, which are harvested in mid-summer, are added with red and white mash as well as the crest.
Kvevris are filled up to ¾ with mash and must. Usually the fermentation starts immediately. The skin is stirred three or four times a day. After the active fermentation, the Kvevris are covered with a piece of wood or shale. Leaves are put between the lid and the edge of the Kvevri and sealed with wet clay and in it is the tube so the CO2 can escape.
Once the alcoholic fermentation and optionally also the biological degradation of acids are completed, the Kvevris are being refilled. New wine from one Kvevri is normally enough to refill two other Kvevris. However, the mash from the red wine is being pressed out immediately after fermentation. Kvevris are being sealed and let alone for purification until the end of February or mid March. The then purified wine is being tapped off and pressed through the mash which settles on the ground of the Kvevri. The yeast wine is blended in at a 50:50 ratio after purification. Then one leaves the wine for a few months for further purification. Before the next grape harvest, the wine is divided up in various little Kvevris and sealed – sometimes for many years. Occasionally a Kvevri is filled at the birth of a son and not opened and drunk before his wedding day.
Empty Kvevris are immediately rinsed and cleaned out with warm water and afterwards rinsed out again with water. Antiseptic herbs are being used as a brush to clean the insides. Kvevris are rinsed out until the water is colorless and odorless. Ashes are being spread over the insides and later Kvevris are being used to burn sulphur. Aging is a quality characteristic for dry wines. Whereas sweet red wine or sparkling wine from West Georgia are not stored for long in Kvevris. Sweet red wines are only produced in certain layers; instead of decomposition raisining defines the aroma of the wine.
From time to time, harvest was in December. After the active fermentation the mash is being pressed and the young wine set aside in the cold. These wines are to be kept cool in summer as well. In some special wine cellars it is possible to produce sparkling wine with residual sugar, due to endothermic reaction between water and certain salts, which composes a natural cooling effect.
It needs getting used to traditional Kvevri wines as well as Sherry or Retsina. Nowadays producing wine in Kvevris is more common in Georgia. However, not all producers stick to the tradition a 100%. There are also linked productions, where Kvevris are used alongside modern devices. Practice shows us, that traditionally pressed and produced wines develop a more harmonic structure and a better aroma then machine-made ones. However, the chances are higher, that a dangerous acescence and fleshly aroma occurs. Stripped Kvevri grapes are lacking a specific nuance which is given to them by the wooden crest of more ripe grapes. However, grapes which are pressed through a roll get an unwelcome vegetable aroma.
In Germany, Charlemagne banned pressing grapes with feet. If, however you can obey that rule depends on the ripeness and the health of the grapes. The period for the mash standing can only be defined in relation to the health of the grapes. If the mash is infected with putrefaction, acetic acid bacteria are being reproduced and act as oxidants for botrytis. In healthy vintage, besides saccharomyces cerevisiae, natural yeast is also being reproduced resulting in interesting aroma shades. Due to the increasing amount of alcohol units during fermentation, the ratio between the different yeast will always be affected in advantage of the saccharomyces cerevisiae. The oxidation before the alcoholic fermentation creates the aroma of dried fruits without any negative traces of acetaldehyde.
The color of red wine fades slightly after fermentation and also the young wine shows a slightly brown shade rather than a purple shade, but this also changes after a while. Employing selected yeast is not sensible with Kvevri wine. Through regulating the time of ripening clear wines can be produced and there are no difficulties in fermentation, even with high quality vintage of 105-110 OE°.
Big Kvevri regulate the temperature for fermentation. For an ideal fermentation at a temperature between 20-28 °C, Kvevris with a holding capacity of 1.000-1.500 liters are best suited. This is also the most common size. Using Kvevri with a holding capacity of 4.000 liters is more the exception. There are even archaeological finds of Kvevris with a double wall, a system to cool the water and a holding capacity with up to 10.000 liters. This however, was probably the leftovers of failed experiments.
The walls of Kvevris are diaphanous for water and air. To close the bigger pores, the insides are palmed off with hydrophobic bees wax. This makes it easier to clean the inside and bacteria are not likely to be able to survive on that surface. Moreover, it is not possible for any liquids to diffuse from the outside. However, the smallest pores are free and therefore enable the wine to breathe. Researching the micro – oxygenation in Kvevris is not very much advanced yet, put plays in theory an important role.
The maceration after the fermentation is important for obtaining harmonic wines. During this time, the wine remains on the lees at a temperature of 12-14 °C. Although the whole wine is in contact with the yeast, they taste better than the once already harvested in December. The yeast cells absorb the bitter tasting phenols of the wine. Autolysis of yeast plays a positive role in this process. Despite of the reductive production of wine, there is no Kvevri wine with sulfated aroma, because the wine is not sulphured and features no deficit in nutrients. The first cutting is done before the first warmth of spring, during summer the wine is being cut again and stored till consumption in smaller Kvevris with a holding capacity of 50-300 liters. Afterwards the wine ages aerobic, this process is similar to the long aging of champagne in a bottle.