Red wine is an alcoholic beverage made from alcoholic fermented grape must, obtained from different dark-coloured (red) grape varieties of Vitis vinifera genus. Some of the most relevant red grape varieties are: Tempranillo in La Rioja, Navarra, Ribera del Duero and Toro appellations; Cabernet Sauvignon and Merlot in the region of Bordeaux; Syrah in the Rhône Valley and queen variety Pinot Noir in Burgundy.
Which are the morphological features of red grapes?
Dark-coloured grapes, as they mature in the vine, get their intense red-bluish pigment in their skin (pomace) where most of the colouring matter is concentrated, the so-called antocian that would later on convey its tinge to the wine. On the other hand, its flesh is colourless but rich in sugars. These sugars will be responsible of the must change into wine thanks to the action of saccharomyces yeasts. Finally, its seeds are rich in tannins and give structure to the red wine.
Red Wine elaboration process…
The process of red wine producing starts at harvest time, from August to October depending on the wine growing area. Northern regions, such as Burgundy or Germany, with a colder climate, have a slow ripening of their fruits, so harvest is delayed. The right moment is when fruit' sugar concentration and desired acidity are reached.
Once grapes are delivered into the winery, they are sift at the vibrating sorting tables, so any fungi damaged berry or those that have not completed the ripening period are rejected. Then, bunches of berries fall directly in the stemming system, to remove the stems, and in the mechanical crushing equipment to slightly break the berries thus releasing grape must. With a peristaltic or eccentric screw pump the pulp (must and pomace) is driven into either concrete or stainless steel tanks or into wood vats, according to the winery's choice.
It must be noted, however, that some wine producing areas omit the stemming process so the stems are also introduced in the vats and tanks, and the resulting wine is more tannic. Everything relays on the variety used, as Pinot Noir for instance has very low tannin and needs a boost to enable their long ageing process; otherwise wine would be too thin.
With the harvest in the tanks, there is the option of a cold pre-fermentative maceration for some days that will enable primary aroma extraction; this might be interesting in case of grape varieties with great scents potential. Anyway, the next step is the seeding of selected yeasts if a controlled fermentation is desired, otherwise spontaneous fermentation is another option as the pomace (skin of the grape) has its own yeasts. Throughout the alcoholic fermentation, yeasts turn sugar into alcohol while releasing carbon dioxide gas (CO2) as a sub product. The complete process takes about two weeks, and meanwhile periodical pumping are performed to obtain the pomace pigments that would tinge must-wine beautifully red. Additionally, open pumping allow must-wine aeration, getting rid of the reduction smell and also activating the fermentation process, slowed down by the CO2 release, keep in mind the entire process is carried out in an anaerobic environment.
Once alcoholic fermentation is finished, winery has the option to continue with the wine maceration in pomace for some days, the so-called post-fermentative maceration. This stage leads to an increase in aroma, colour and tannins in the red wine. Besides this, after fermentation, the next step is the drawing out of the tanks or vats, where pomace is definitely removed from the red wine. The skin remains are introduced in a vertical hydraulic press or a membrane press that will enable, through pressing, the boosting of the richest in tannins and astringent wine that will be used at the end of the vinification process to furnish structure in case it should be necessary. Thus, press wine is kept separately in steel tanks or barrels until the very last moment. After pressing, the solid remains (orujo) are used in the manufacture of distilled liquors.
Usually red wine is racked into steel vats for a second fermentation: malolactic fermentation, where the action of lactic bacteria turns strong acids such as the malic (green apple) into smooth acids such as lactic (milk). This process might take up to a month to be completed and it needs a temperature over 20ºC, so in cold areas it does not take place until spring time.
Then, and according to the type of red wine that is being sought, it can be racked into barrels for a Crianza red wine. In case of Young red wine only some months resting in the stainless steel vats is necessary. Correspondingly to the ageing time in barrels and bottle there are different wine categories: Young crianza, Crianza, Reserve and Grand Reserve.
The fining or clearing is one of the last stages previous to marketing, where fining agents, as casein, egg-albumin, bentonite and isinglass, are added to wine to eliminate any tartrate or colloidal suspended matter that might cloud wine. Subsequently and also optionally, wine can be filtered with plate pads or by diatome soils, rendering red wine steadier biologically speaking.
Finally, red wine is bottled and ready for distribution in the market.