Poetically, we could say that wine is the product of the sum of soil generosity, climate complicity, and the enthusiastic work of man.
If the soil allows it, the roots of the vine plant are capable of reaching great depths to find nutrients and water to sustain it through the summer rigours. Land’s orientation and inclination will affect the amount of sunshine and therefore the ripening of the grapes.
Like all plants, vines depend greatly on their enviroment. Soil and climate are highly influential determinants for growth and production for the processing of the final product, the wine.
Consequently, climatology has a definite impact. Vine growers fear spring frosts, extreme droughts, and late rains before the harvest, that complicate growth and promote diseases. All these climate factors vary from year to year, from harvest to harvest, and have given rise to the concept vintage year.
Finally, man acts both in culture matters (pruning, treatments, weeding, etc.) and in the production process.
Human involvement is essential in the production process since the best of grapes would become the worst of vinegars if man does not guides, directs and controls the transformations that occur during fermentation and wine aging. Nevertheless, 90% of a wine is based on the grapes from which it originates. The job of a good enologist is to obtain exeptional wine from exeptional grapes, but he/she will never be able to obtain an excellent wine from mediocre grapes.
All these factors make clear the phrase “Wine is processed, not manufactured. It is unique, unrepeatable and changing, no two wines are alike.”. Therefore, the same wine, from one harvest to the other can suffer substantial variations that make certain vintage years better than others and vice versa.
Following a more scientific line of argument, we will say that wine is a product obtained from the fermentation of grape juice (must). Juices contain from 15% to 20% of glucose and fructose, which by the action of selected yeasts, become ethyl alcohol and CO². During this fermentation process the alcohol reaches concentrations of 7% to 15% of volume, or even greater (wine’s alcohol content).
In this production process, some substances, such as tartaric acid, malic acid, sulfur dioxide (sulphites) and tannin, are added to the must, as well as others that will prevent the growth of undesirable microorganisms that are present in must.
The wine obtained is stored in big barrels for filtration, sedimentation and maturation. The changes during this aging process are mostly due to the action of certain enzimes, as well as the effect of complex physicochemical processes.
The wine’s flavor and aroma depend on the must’s origin and quality, and on the yeasts that have intervened in the fermentation and vinification processes.
To obtain white wines certain grape varieties are used. Their musts are fermented separately from the seeds and skin (solid matter left after pressing the grapes). While red wines are also obtained from certain grape varieties, contrary to the whites their musts are fermented with seeds and skin.
Regarding rosé and claret wines, they are obtained when the must is fermented with seeds and skin during a short period of time, inferior than that of red wines. That is why they are darker than the whites and lighter than the reds.