How is wine produced? The winemaking process of red, white and rosé wines
Wine is an important component of the Mediterranean diet and winemaking is very common in Mediterranean countries. The origin of wine dates back to the times of ancient Greece, the Minoan and Mycenaean periods, and the wine culture has spread to other countries. Nowadays, Italy, France and Spain are the three main producers of wine in the world and Languedoc-Rouissilon (a French region) is the largest area of wine production in the world. Greece and Portugal are also important wine producers. Table 1 shows some of the main European wine grape cultivars.
With the exception of Muslim countries, wine (especially red wine) is consumed in moderate quantities in the entire Mediterranean area. Meal consumption is important with regard to alcohol metabolism, as it is absorbed by the stomach and this process is slowed down by the simultaneous presence of food, which reduces its negative effects. The intake of high quantities of alcohol (binge drinking), which usually happens during the weekend in many countries, is not part of the Mediterranean culture, although it is becoming an increasingly common habit.
Table 1: Some common wine grape cultivars, cultivated in countries representing the largest wine producers in Europe.
Wine is a product of the fermentation of grapes of which many varieties exists. The type of grape used, the different growing conditions of the plants, the winemaking techniques and the degree of aging, determine the quality of a wine, which provides a very wide variety of products, different in taste and chemical composition. Most of the most known crops have been developed in France, which has a long tradition: just think about Pinot noir, Cabernet or the famous Champagne.
To produce wine, the grapes are cleaned of leaves and other residues from the plant, and then pressed. This process results in the must which is then left to macerate, so that the pulp, the skins and the seeds can release some important bioactive substances and enzymes. This phase is very short for white wines, one of the reasons why they contain less bioactive compounds, whereas it is longer for red wines. The ethanol is produced by fermentation, which in the case of red wines accompanies the maceration phase of the must. The alcohol that is produced during the fermentation process, acts as a solvent for the phenolic compounds and the anthocyanin contained in the grapes and can also contribute to their release. The must then undergoes a process of squeezing and a second phase of fermentation, known as “malolactic” because it involves the conversion of malic acid into lactic acid, which helps to improve wine’s flavour. Grapes grown in hot climates do not require this second stage of fermentation, as the content of malic acid is very low. The wine is then aged in large stainless-steel containers, a phase during which further tannins are produced.
Red wine production – The production of red wine (or “vinification”) is a process characterized by the contact between the pomace and the must during fermentation. Thanks to the dissolving power that characterizes alcohol and the temperature at which the vinification process is performed (usually between 26 and 30°C), the coloured pigments (anthocyanins) and the tannins contained in the grape skins pass into the must, and can then be retrieved in the wine after separation between the solid and liquid parts.
The fermentation and the maceration phases usually last between six and ten days, depending on the content and the “extractability level” of the substances present in the treated grapes. Some high-quality wines have a very long maceration phase (up to forty days), in order to extract more of the peel content.
Subsequently, the solid parts are pressed in order to recover the part of the wine that remains in contact with the peels, and all the liquid mass is stored in barrels, in stainless steel containers or in other containers suitable for the refining phase, i.e. when further aromas produced with the aging of the wine are released. For red wines, this phase can last for many years.
White wine production – In this case, the fermentation process takes place without contact between the pomace and the must, i.e. without maceration. This type of winemaking involves the separation of the grapes from the stalks before pressing. This is then known as “crushing” by separating the must from the fraction containing the peels. In practice, this fraction is immediately used for pressing for the recovery of all liquid fractions and does not come into contact with the must. By removing the peels (which contain most of the pigmented substances), as well as the grape seeds, it is possible to produce white wines also using red grapes.
The must is normally decanted, filtered and centrifuged to obtain the best clarity and fineness. The making of white wines is quite critical because air contact must be avoided to prevent oxidation, which can lead to a worsening of the organoleptic qualities of the wine. When this happens, the wine takes on a colour defined as “chestnut broth” as well as a cooked flavour.
The vinification temperature must be maintained between 18 and 22°C, generally using double-walled insulated fermenters. Apart from a few special white wines that are aged for a long time, most of these wines should be consumed within two to three years after harvesting. The refining phase actually lasts only a few months since white wines are indeed fresh and fragrant wines, that people drink when they are still pretty young.
Rosé wine production – In the production of rosé wines one of the most common techniques is to leave the peels in contact with the must for a short period of time, i.e. enough to enable the appearance of colour, which can range from very pale pink to dark pink.
The main active compounds of wine are ethanol (8-15%) and some phytochemical compounds, especially polyphenols. Red wine contains about seven times more polyphenols than white wine, for a total of more than 200 different compounds, even if associated with different products. The fermentation of the must substantially changes the composition of the wine compared to the simple grape juice, but it seems that even the latter has beneficial effects on health, good news for people who don’t drink! The fermentation of red wines takes place in the presence of skins, which involves enrichment in polyphenols, whose concentration increases further with ageing.
Like many other types of fruit, grapes also contain many flavonoids, in the form of glycosides hydrolyzed during fermentation, which makes them even more bioavailable and the presence of ethanol further increases their solubility. Other compounds contained in wine are resveratrol, hydroxycinnamic acids (such as caffeic acid) and tyrosol, which is formed by tyrosine during fermentation.
 Freshly crushed fruit juice that contains the skins, seeds, and stems of the fruit.