ABSTRACT
Wines are highly valued beverages produced from grape juice, being grapes quite complex fruits from the chemical point of view. During wine production, a series of physical, chemical, and biochemical processes take place, many of them having a deep in‹uence on the nal wine chemical composition. Different enzymatic, oxidative, hydrolytic, and chemical-dissolution processes predominate before fermentation. During fermentation, major changes are due to the metabolism of yeast that secretes to the medium large amounts of secondary metabolites, many of which have relevant sensory properties. After the alcoholic fermentation, biological changes are slower yet very important, since dead yeast cells still display enzymatic activities and lactic bacteria are active. Later on, changes still are slower, but very relevant from the sensory point of view. In this last step of aging, most changes are mainly of chemical nature: acid hydrolytic processes, chemical rearrangements, oxidations, reductions, polymerizations, adduct formation, or extractions from wood, to name some of the most relevant. This large series of processes, consequence of the different technological options, introduce a huge chemical complexity and also can introduce a relatively large chemical diversity. The chemical complexity manifests not only on the large number of different molecules present in the medium, but on the complex and for the most unknown interactions that these molecules can exert between them. Similarly, the chemical diversity will manifest on the relatively large ranges at which some compounds will be found, depending on the wine type, origin, age, or wine making method.
