Benzothiadiazole (BTH) and methyl jasmonate (MeJ) have been described as exogenous elicitors of some plant defense compounds, polyphenols among them. The objective of this study was to determine whether the application of BTH or MeJ to grape clusters at the beginning of the ripening process had any effect on the accumulation of the main flavonoid compounds in grapes (anthocyanins, flavonols, and flavanols) and the technological significance of these treatments in the resulting wines. The results obtained after a 2 year experiment indicated that both treatments increased the anthocyanin, flavonol, and proanthocyanidin content of grapes. The wines obtained from the treated grapes showed higher color intensity and total phenolic content than the wines made from control grapes. The exogenous application of these elicitors, as a complement to fungicide treatments, could be an interesting strategy for vine protection, increasing, at the same time, the phenolic content of the grapes and the resulting wines.

Proanthocyanidins are important for wine quality since they participate in astringency, bitterness and color. Given the localization of proanthocyanidins in the berry (skin and seeds), different methods have been developed that help to modulate the release of these phenolic compounds. In this study, the effect of two low prefermentative temperature techniques (cold soak and must freezing with dry ice) and the use of macerating enzymes has been studied during the vinification of three different varietal wines (Monastrell, Syrah and Cabernet Sauvignon) to assess their influence on wine proanthocyanidin concentration and composition. Syrah wines showed the lowest proanthocyanidin content, together with the lowest mDP and the highest percentage of galloylation in its proanthocyanidins. Monastrell and Cabernet Sauvignon wines showed similar proanthocyanidin concentration. The application of the low temperature prefermentative maceration (cold soak) was the most effective treatment, increasing the proanthocyanidin concentration in Monastrell and Cabernet Sauvignon wines although neither of the treatments had any effect on Syrah wines. As regards the effect of the different treatments on the proanthocyanidin composition, the results seem to indicate that the observed increases were mainly due to an increase in seed proanthocyanidins, even in the case of cold soak treatments, which occur in the absence of ethanol, suggesting that ethanol is not so crucial in the extraction of seed proanthocyanidins.

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The purpose of this work was to determine the influence of vinification technique (maceration temperature and clarification method), storage temperature, and length of storage time on the phenolic compounds and color of young red wines. Multivariate analysis of variance and principal component analysis pointed to significant differences among all of the variables according to vinification technique and length of storage time. Storage temperature did not cause significant differences between some of the variables. The best color characteristics were obtained when low-temperature maceration wines were clarified with polyvinylpyrrolidone. Color quality also improved with lower storage temperature.