Effect of malolactic fermentation in barrels or stainless steel tanks on wine composition. Influence of the barrel toasting

Abstract

Ellagitannin, anthocyanin and woody volatile composition of Cabernet Sauvignon wines aged in oak barrels for 12 months was evaluated. Depending on the container where malolactic fermentation (MLF) was carried out, two wine modalities were investigated: wines with MLF carried out in stainless steel tanks and barrel-fermented wines. Three toasting methods (medium toast, MT; medium toast with watering, MTAA; noisette) were considered for ageing of each wine modality. Sensory analyses (triangle and rating tests) were also performed. Two-way ANOVA of the raw experimental data revealed that the toasting method and the container where MLF took place, as well as the interaction between both factors, have a significant influence (p < 0.05) on ellagitannin, anthocyanin and woody volatile profiles of Cabernet Sauvignon wines. The toasting method of the barrel influenced significantly the ellagitannin composition of both wine modalities. In the case of MT toasting, wines fermented in stainless steel tanks showed higher ellagitannin content than barrel-fermented wines (p < 0.05), whereas the opposite behaviour was observed for the MTAA toasting. In contrast, similar concentrations of individual ellagitannin compounds were found for both wine modalities in the case of Noisette toasting. Barrel-fermented wines presented significantly lower contents of individual anthocyanins than those which carried out MLF in stainless steel tanks (p < 0.05). These results suggested a higher potential interaction of anthocyanins with oak wood components when MLF occurred in barrels. Greater trans-whiskey lactone levels appeared in wines which undergo MLF in MTAA and Noisette barrels than in the stainless steel tanks. The same behaviour was observed for cis-whiskey lactone, vanillin and syringaldehyde contents for MT and Noisette toastings. Even if it is known that lactic acid bacterias are able to increase oak wood volatiles levels during MLF, it is the first time in the literature that has been reported according to barrel toasting. This observation is crucial as oak wood volatile enrichment during ageing contributes to wine aromatic complexity. All these chemical results led to significant differences in the sensory analyses. Regardless of the toasting method, judges preferred barrel-fermented wines in terms of gustative tasting (>55%). Furthermore, both wine modalities differed significantly with regard to the vanilla and/or overall woody aroma in the case of MT and Noisette toastings (p < 0.05). On the whole, the container where MLF takes place seems to play an important role in i) extraction of ellagitannins from oak wood into wine, and ii) conversion of aromatic precursors into their corresponding woody volatiles. Nevertheless, the barrel toasting was found to condition the accessibility to ellagitannins, as well as the availability of those aromatic precursors. The interaction of both factors influenced the sensory results obtained.