The influence of storage on the “chemical age” of red wines

Storage conditions and duration have a considerable influence on wine quality. Optimum temperature and humidity conditions may improve wine quality through ageing, while incorrect or excessively long storage leads to negative results. In order to evaluate the global effects of storage on red wine composition, 20 Sangiovese wines were stored in two different conditions (cellar or house) for a period of 2 years and analysed every 6 months. Untargeted LC–MS analysis showed various putative markers for the type and length of conservation (i.e. pigments, flavanols, pantothenic acid etc.), while targeted LC–MS confirmed and expanded these results within specific metabolic groups. The results of multivariate analysis showed that wines stored in the cellar changed little even after 2 years of storage, while wines stored in typical domestic conditions (house) developed approximately four times faster, reaching a composition similar to wines stored in the cellar for 2 years after just 6 months. The formation of several monosulfonated flavanols during domestic ageing provided the first evidence in wine of a reaction between wine tannins—both catechins and proanthocyanidins—and the exogenous antioxidant bisulfite. Moreover, ageing in domestic conditions appeared to induce an accelerated decrease in wine pigments, while specifically promoting the formation of pinotin A-like pigments and the hydrolysis of flavonol glycosides.     

Contribution by Saccharomyces cerevisiae yeast to fermentative flavour compounds in wines from cv. Albariño

A comparative study was made of the fermentation products of Spanish Albariño wines produced with spontaneous yeast flora and an indigenous selected Saccharomyces cerevisiae strain (Alb16). The content of fermentative volatile compounds was determined by gas-chromatography-FID. Fifteen compounds (5 alcohols, 7 esters and 3 acetates) were identified in the two Albariño wines studied. Higher alcohols, ethyl esters (except ethyl hexanoate and ethyl octanoate) and acetates were in greater concentration in the spontaneous fermentation wine than in that with selected Alb16 strain. Principal components analysis showed good separation between the different wines.     

Exploring the biodiversity of two groups of Oenococcus oeni isolated from grape musts and wines: Are they equally diverse?

One hundred and four Oenococcus oeni isolates were characterised by the carbohydrate fermentation (CH) profile and DNA fingerprinting. Forty-four isolates came from grape must, and 60 from wines sampled at the end of alcoholic fermentation or during malolactic fermentation. The grape must isolates fermented more CH than the wine isolates. In genotypical terms, no clear boundary between grape must and wine isolates was found. Diversities were deduced by considering the isolates of grape must and of wine separately and jointly. By considering only CH fermentation abilities, the group of grape must isolates gave higher diversity index (DI_CH) values than those isolated from wine; i.e., these isolates were metabolically more diverse. The contrary occurred when the DNA fingerprints were used to calculate DI_RAPD-VNTR: wine isolates were genotypically more diverse than grape must ones. With a polyphasic approach, which considered metabolic and genotypic data, the diversity index of both isolate groups (from grape must and wine) was the same, 0.993, which was slightly lower than that calculated from all the isolates (0.997).