The drying process consists of specific technologies which involve a partial removal of the grape water, which leads to a variable drop in the product weight by up to 35-40%.
The length of the process ranges from three weeks to four months and involves a series of compositional modifications in the grapes:
- increase in acidity due to the concentration of tartaric acid and simultaneous modification of acidity as the malic acid present is partly degraded during the process;
- increased sugar content;
- increased content of polyphenols;
- changes in the aromas of the grapes.
It can be made in different ways depending on the oenological results to be achieved. In Valpolicella, the grapes are harvested and left to rest in closed rooms. Currently, the drying process sees different execution methods. The " peagnà" is a very ingenious system still used, and that is a complex structure for the framing of bamboo canes rack, locally called "aréle" or "tavoloni".
The grapes selected and collected in baskets or boxes are carefully placed on the racks after further selection: their integrity must be maximum, thus ensuring their health during conservation; the large tables are then fixed on the structure of the “peagnà” with wooden pegs (“caùci”) to form a series of overlapping ranks.
In the 1950s, wooden crates were introduced (a solution still available today but often replaced with plastic material). In this case, the grapes are selected in the field and placed directly in a single layer in the crates, which are then stored in specific rooms intended for drying: the fruit cellars. The drying period for the grapes destined for the production of Amarone and Recioto ranges from 90 to 120 days.
Climatic conditions not favourable might affect the health of the grapes. In this case, further manual sorting of the bunches and deteriorated berries is carried out. The drying process has progressed in the last 25-30 years. The first technological developments kept the grapes healthy when resting. Too rainy and humid autumns and winters could cause the grapes to lose their qualitative potential due to attacks by Botrytis Cinerea.
Even climate change, with increased temperatures and consequent earlier harvests and all related problems, can potentially compromise the qualitative result.
This led to an initial development of technology and the creation of integrated drying systems that see ventilation and air conditioning keep the grapes in good condition even when the weather is not in favour (i.e. high humidity and temperatures). This technological development has allowed Amarone to reach its current notoriety.
The drying process in history
In ancient times, sweet wines, obtained by drying the grapes, met needs of a practical nature, aimed at longer-lasting conservation of the wine and, at the same time, at its strong "resistance" during transport. The drying process, aimed at concentrating the sugar within the berry, was carried out directly on the plant or in the sun. Only later, it was carried out in the fruit cellar.
The Greeks, masters of drying, obtained the classic straw wines by twisting the peduncle of the bunches of the Psithia variety left on the plant.
In the Middle Ages, all Greek straw wines came from Moscato and Malvasia grapes, which were very widespread in Italy; in the same period, Spain produced the wine of Malaga and Alicante and France the sweet wine obtained from Grenache, while Sardinian sweet wine came from Cannonau grapes and Veneto got the wine from the red Tokay variety. The hot-arid Mediterranean weather unites these wines and is necessary to obtain the withering on the plant or in the sun (on mats spread on the ground or on the roofs).
In the northern areas, the straw wines became common much later and were, instead, obtained by drying them in specially ventilated rooms (fruit cellars), to prevent the grapes from getting wet with the rains or with the night dews, optimal substrates for the attack of moulds, in particular of Botrytis cinerea. Noble rot, always caused by this fungus, represented the means through which it was possible to obtain sweet wines in humid climates, but at the same time windy and cold, of northern European countries, in which, the late harvest is still associated with a short drying period in the loft.
The drying process in the world
Botrytis cinerea in noble form is the main dehydrating force of Hungarian Tokay, produced with the Furmint, Harslevelu and Muscat vines; similarly, the Sauternes Bordeaux, deriving from late harvests of botrytized grapes (noble rot) of the Semillon, Sauvignon blanc and Muscadelle vines.
Many historical, traditional, climatic, pedological and genetic factors come into play in the production of straw wines, together with human ones, since it requires specific high-profile knowledge.
Straw wines represent a range of products of notable quality value in the Italian and world enological scene.
The range of Italian straw wines is wide and generally includes white wines, such as Recioto di Soave, Passito di Chambave. Passitos from the Islands (Passito di Pantelleria. Malvasia delle Lipari, etc.), Sciacchetrà from the Cinque Terre, Vin Santi Toscani; while among the red wines, the most significant ones are Amarone and Recioto from Valpolicella and Sforzato from Valtellina.
Drying process and over-ripening process
Unlike other fruits that can ripen even after harvesting (such as apples, peaches, tomatoes, kiwis, etc.), grapes can only complete the ripening process on the plant.
Drying in the fruit cellar is an oenological technique mainly adopted for the aspects related to the concentration of sugars and other solutes occurring following the partial dehydration of the grapes put to rest after harvesting.
The increase in the sugar level, which recalls the accumulation of sugars that the mother plant conveys to the berries during ripening, has sometimes led to call the drying process with the term over-riping. However, this term is not quite adequate, since the processes occurring in the grapes during post-harvest drying are different and peculiar to over-ripening. This can only occur in bunches left on the plant after reaching commercial maturity and gives the grapes and the resulting wines the organoleptic characteristics of overripe fruit.
The grapes left to rest in the fruttaio see the activation of different metabolisms, which significantly modify the phenolic and aromatic framework and which, in traditionally slow processes, give the wines the peculiar notes of drying.
