Maria-Pilar Sáenz-Navajas,* Jose-Miguel Avizcuri, Dominique Valentin, Blanca Lacau, Cristina Baron, Jesús Astrain, Purificación Fernández, and Vicente Ferreira
*Laboratorio de analisis del aroma y enologia (LAAE), Department of Analytical Chemistry, Universidad de Zaragoza, Instituto Agroalimentario de Aragin (IA2) (UNIZAR-CITA), Associate unit to Instituto de Ciencias de la Vid y el Vino (ICVV) (UR-CSIC-GR), C Pedro Cerbuna 12, 50009, Spain (maria@saenz.info)

During winemaking, the oenologist must decide how to handle grapes that enter the winery with an acceptable concentration of sugars or acids but with immature tannins. Such grapes generate wines with green, aggressive, or hard (noted as GAH onward) character which influence consumer acceptance of the product. Such decisions are currently based on empirical experience due to the lack of objective criteria. Better chemical and sensory knowledge of immature tannins would allow managing this GAH character efficiently during winemaking. The present work isolates and identifies the group of compounds responsible for the GAH character in wine.

Thirty-eight wines with a priori different degrees of GAH were submitted to sensory analysis by a panel of 25 wine experts. Thirteen attributes and two multidimensional terms (preference and GAH) were rated. The GAH concept was correlated negatively to preference and positively to aroma (vegetal) and in-mouth terms (astringency, green, and dry tannins). Four wines with different degrees of GAH were fractionated by solid-phase extraction and semipreparative liquid chromatography. Six odorless fractions (F1 to F6) were isolated from each wine and subjected to characterization of in-mouth sensory properties.

Fractions F3 and F5 induced the highest aggressive character perceived in-mouth among the fractions studied. Fraction F3, which mainly contained anthocyanin-derived compounds with low molecular weight (lower than trimers) and contained an average of 50% of the overall polyphenolic compounds of the original wine, was especially astringent for three out of the four wines studied. In the fourth wine, this fraction was mainly described as “sticky.” Fraction F5 contained polyphenols of high molecular weight (higher than trimers) and, on average, ~15% of the overall polyphenolic content of the original wine. This fraction was especially astringent and dry for the wine scored highest in GAH. These results are promising and suggest that the developed chemosensory approach succeeded in isolating a group of compounds potentially involved in the green, aggressive, and hard character of wines.

Funding Support: Spanish Ministry of Economy and Competitiveness (MINECO) and the European Union (FEDER Funds)