Insights on the chemical basis of the astringency of Spanish red wines.

The main goal of the present study is to provide an insight on the role played by non-volatile molecules on the different in-mouth attributes, particularly astringency. For achieving such goal, the main in-mouth sensory attributes of 34 oaked Spanish red wines were measured by a trained panel. The wine content in 30 sensory-active molecules was analysed by different HPLC based methodologies together with classical enological parameters and two proanthocyanidin indexes. Fourteen compounds (aconitic acids, polymeric proanthocyanidins, caftaric, caffeic and coutaric acids and seven quercetins) were found to be at concentrations above reported taste thresholds and to have a reasonably high range of occurrence. Two highly statistically significant models for astringency were built with those compounds. Even if the models could not be fully validated by sensory addition experiments, the research has demonstrated that wine astringency is driven by polymeric proanthocyanidins and by certain phenolic acids, the rate trans/cis-aconitic acid and flavonol profiles. The research has highlighted the existence of extremely complex interactions between non-volatile compounds on the in-mouth sensory perception. Particularly remarkable is the lack of additivity and potential antagonism found between the pairs cis/trans-aconitic acids, between aconitic and caffeic acids and between quercetin-3-O-galactoside and quercetin-3-O-glucoside. Also remarkable was the sweetness×astringent interaction and the matrix-dependence of the sensory responses elicited by flavonols. These results suggest the need for new paradigms and experimental procedures for fully decoding the real sensory relevance of individual non-volatile compounds in the overall wine flavour.

Evaluation of the impact of initial red wine composition on changes in color and anthocyanin content during bottle storage.

Sixteen commercial red wines, selected to cover a different range of color and total polyphenols index (TPI), were stored at 25°C during 6months under controlled and different oxygen additions (0, 1.1, 3.1, 10.6 and 30.4mgL(-1)) during the bottling process. Changes in color and the anthocyanic composition were evaluated using transmittance spectra and UPLC-MS-UV/Vis respectively. Results reveal a general pattern in the evolution of wines. However, different patterns of evolution related to initial wine composition, especially to TPI, were observed. Wines with higher TPI had a lower evolution, whereas wines with lower TPI showed a higher evolution and greater variability in behavior. In general, oxygen seemed to accelerate all changes observed during aging although the oxygen effect was more limited than the effect of the storage time. These results are relevant for wine experts and help explain the evolution of wine at the bottling stage.

Study of Chardonnay and Sauvignon blanc wines from D.O.Ca Rioja (Spain) aged in different French oak wood barrels: Chemical and aroma quality aspects.

This study discusses chemical data corresponding to the analysis of twenty-one wood-extractable aromatic compounds in twenty-four different barrels varying in the toasting level at three sampling times: at the end of the alcoholic fermentation and after 5 and 12months of aging. Twelve barrels contained monovarietal Chardonnay wine while the other twelve barrels contained Sauvignon blanc wine. The levels of nearly all the analyzed compounds increased with the aging time, with the exception of vinylphenols and methyl vanillate, which decreased. These latter compounds had significantly higher levels in the Chardonnay wines than in the Sauvignon blanc. Furfural, guaiacol and vanillin derivatives increased with the toasting level. ANOVA study showed significant interactions between the toasting level and aging time as well as between the variety and aging time, which revealed significant differences in the levels of the compounds studied in the wines dependent on the toasting level, variety and aging time. Quality perception based exclusively on orthonasal aroma stimuli was evaluated by a panel of Spanish wine professionals in 12-month aged wines belonging to both grape varieties. Experts from D.O.Ca Rioja aroma did not share a common aroma quality concept for aged Chardonnay and Sauvignon blanc wines. Considering the cluster formed by the majority of experts (76%) for the Chardonnay and cluster 1 (56%) for Sauvignon blanc, quality scores were negatively correlated with the concentration level of 4-vinylphenol and positively with the concentration level of (E)-isoeugenol. The opposite was observed for cluster 2 (44%) identified for Sauvignon blanc wines.

Contribution of non-volatile and aroma fractions to in-mouth sensory properties of red wines: wine reconstitution strategies and sensory sorting task.

This work explores to what extent the aroma or the non-volatile fractions of red wines are responsible for the overall flavor differences perceived in-mouth. For this purpose, 14 samples (4 commercial and 10 reconstituted wines), were sorted by a panel of 30 trained assessors according to their sensory in-mouth similarities. Reconstituted wines were prepared by adding the same volatile fraction (coming from a red wine) to the non-volatile fraction of 10 different red wines showing large differences in perceived astringency. Sorting was performed under three different conditions: (a) no aroma perception: nose-close condition (NA), (b) retronasal aroma perception only (RA), and (c) allowing retro- and involuntary orthonasal aroma perception (ROA). Similarity estimates were derived from the sorting and submitted to multidimensional scaling (MDS) followed by hierarchical cluster analysis (HCA). Results have clearly shown that, globally, aroma perception is not the major driver of the in-mouth sensory perception of red wine, which is undoubtedly primarily driven by the perception of astringency and by the chemical compounds causing it, particularly protein precipitable proanthocyanidins (PAs). However, aroma perception plays a significant role on the perception of sweetness and bitterness. The impact of aroma seems to be more important whenever astringency, total polyphenols and protein precipitable PAs levels are smaller. Results also indicate that when a red-black fruit odor nuance is clearly perceived in conditions in which orthonasal odor perception is allowed, a strong reduction in astringency takes place. Such red-black fruit odor nuance seems to be the result of a specific aroma release pattern as a consequence of the interaction between aroma compounds and the non-volatile matrix.