Viticulture should not be confused with viniculture. Viniculture deals with the use of grapes in winemaking while viticulture can include grape harvesting, commercial sales of grapes, making of raisins or other aspects of grape production.Viticulture has a long and rich history, and it is believed that winemaking closely followed the cultivation of grapevines. A winery, believed to be from the 4100 B.C was discovered in Vayots Dzor, Armenia. Similarly, there are evidences of grape harvesting that dates back to 3200 B.C in the Near East. Domestication of grapes and winemaking is believed to have begun in eastern regions between 3000 B.C to 2000 B.C. Viticulture continued to flourish into the middle ages by catholic monks and it is still thriving.
With a production approaching 50 million hectolitres a year, France and Italy are the main wine producers in the world, with a market share fluctuating between 16% and 18%. Spain, USA and Argentina follow. A positive trend of the so-called “New World” is also recorded: Australia, New Zealand, Chile and South Africa are growing their own “international vine varieties”, that is those that reproduce wine productions of “known” tastes, appreciated all over the world. Currently, demand is moving towards medium-high quality products in all countries, quality intended as technology applied to wine production, which is more and more often a priority for both producer and consumer. This evolution “from quantity to quality” is at the basis of the success of the “New World” wines and is starting to be adopted in Europe too. Italy is particularly interested in the evolution of wine markets and occupies a position on the world stage that commands respect: largest producer, largest exporter as to quantity and second exporter as to value. In recent years, the sector is abandoning its mainly agricultural connotation and presents itself increasingly more often as an important industry, characterized by high levels of competitiveness and technology. On a global level, the wine sector is looking for constant improvement, which is pushing producers to optimize the production process, adopting cutting-edge technical and management solutions
The wine chain and wine-making cycle:
The temperature variable and its control play a vital part in the wine-making technological process and in the transformation of must into wine. The optimal temperature value to aim for and maintain varies according to the wine-
making process, its various phases and the oenologist’s choices. In general, it is possible to identify two operating cycles: vinification of red grapes (red wines) and vinification of white grapes (white and rosé wines). The main difference between the two cycles is, in the vinification of red grapes, maintaining the skins in contact with the must to give the product aroma and colour through maceration. On the other hand, in the vinification of white grapes, a soft pressing is carried out immediately to prevent the must from being contaminated by other elements. This second type of vinification applies to sparkling wines too, characterized by the production of froth due to the presence in the bottle of carbon dioxide produced by fermentation.
To obtain a sparkling wine, you can follow two methods: the Classical Method (or Champenois), characterized by slow re-fermentation in the bottle or the Martinotti-Charmat Method where, on the other hand, the sparkling process takes place in the autoclave.
The most important phase of each wine-making cycle is surely fermentation. Fermentation is an exothermic reaction that transforms 90% of sugar into alcohol, that is the must into wine. The oenologist establishes exactly the length and intensity of the transformation, parameters that contribute in a decisive way to the quality of the final product and its organoleptic properties. Fermentation increases the temperature of the mass up to values incompatible with the life of the yeasts responsible for the reaction (35 ÷ 40°C). For this reason, this must take place at monitored and controlled temperature, with modern and flexible systems capable of offering both cold and warmth (i.e. heat pump systems).
The importance of the wine-making technological system in the wine industry
The evolution from quantity to quality in wine- making has required increasingly greater control of all the production process phases, where the cooling system becomes far more important.The use of the cold/heat in the cellar is necessary to guarantee the various temperatures during the different phases of the wine-making process:
● Lowering the white grape must temperature to about 12°C for static decanting treatments;
● Maintenance of the fermentation temperature (17 ÷ 20°C for white wines; 25 ÷ 28°C for red wines);
● Quick cooling to block fermentation;
● Product clarification and conservation operations;
● Wine cold tartaric stabilisation.
Moreover, anticipating the grape harvest from the end of September to the end of August has made the use of a suitably sized cooling system that can meet all the requirements of the winery, even more necessary.In the oenological sector too, the first classification of the cooling systems is as follows:
● Direct cooling;
● Indirect cooling.
In the first case, the heat exchange between coolant and must takes places directly inside the evaporator. In the second case, on the other hand, a solution with a low freezing point (glycol-water) is used.With both the direct and indirect system, reaching the product temperature set point and maintaining it is obtained in two ways:
Adjusting the flow of the working fluid can take place by adjusting the opening/closing ofvalves located near the vinificator, or acting directly on the pump ON/OFF on the secondary branch.
Internal mode cooling
Reaching the preset temperature
During the static decanting, stabilization and clarifying phases, the priority is reaching the set temperature of the must/wine as quickly as possible.This can be done in internal mode using immersed coil exchanges, refrigerated plates,
jacket or mantle heat ex-changers. This mode has the disadvantage of having an uneven temperature distribution inside the product.In fact, very near the component, cooling is quick while, near the wall, the product cools down more slowly.This phenomenon of thermal layering is much more accentuated vertically and for large volumes. It is therefore necessary to activate convective motions using rotating parts or pumps, checking that this does not affect the processin progress. The oenologist or cellarman must therefore be able to control the stirring device and they will use it only when this does not affect the process phase in progress.
What was said about lowering the temperature applies. It is possible to reduce the lack of homogeneity in the treatment with a mixer, in order to allow all the product to touch the surface of the cooling component: this way it is possible to maintain a 0.5°C hysteresis compared with the set value.
The components normally used are:
● Thermal exchange jacket;
● Coil exchanger;
● Refrigerated plate
(normally called biscuit).
In modern wineries, stainless steel tanks are used, provided with a cavity within which chilled water flows, to control the must/wine temperature. Immersion ex-changers (either plate or coil) are used above all in:
● Small stainless steel modern tanks
without an external jacket;
● Old stainless steel tanks not fitted
with an external jacket;
● Concrete tanks.
External mode cooling
Reaching the preset temperature
In external mode cooling, lowering the must or wine temperature takes place in heat ex-changers outside the vat: according to the particular process phase, the best component can be chosen (shell and tube, tube in tube, scraped surface, plate ex-changer).Unless the system does not allow it, the external solution for decanting, clarifying and stabilising is the recommended solution.
With this cooling mode, temperature control during maintenance is less precise, with temperature fluctuations that can reach even 5 ÷ 6°C.
The cellar system
The cellar system consists of various rooms, each one characterized by particular thermohygrometric conditions to be maintained:
● Storing room for young wine: 15 – 18°C;
● Ageing cellars: 12 – 18°C with a percentage of relative humidity included between 75 and 85%;
● Bottle store: 18 – 20°C;
● Drying rooms: 25 – 30°C with relative humidity included between 40 and 70%.
A solution for each room
● Vinification: heat pumps / chillers
● Tasting room and offices: fan coils together with heat pumps / chiller
● Storage, ageing (in the bottle), barrique / barrel room: air handling unit, thermoventilation
units together with heat pumps / chiller