Late harvesting of grapes leads to change in wine aroma, study finds

A recent study published in the Oeno One journal has highlighted the critical role of harvest timing in wine production, demonstrating its influence on the sensory and aromatic characteristics of the final product. The study investigated how the harvest date affects the aromatic intensity of herbaceous notes, fresh fruit, and candied fruit in Merlot and Cabernet-Sauvignon grapes, as well as in the wines produced from these varieties during the 2012 and 2014 harvests.

The study found that adjusting the harvest date modulates the aromas of young wine and affects the intensity of candied fruit aromas in both Merlot and Cabernet-Sauvignon. Surprisingly, there was no correlation between the intensity of candied fruit aromas in the must and in the wine. To observe an impact on the intensity of candied fruit aroma, it was necessary to delay the harvest date of Cabernet-Sauvignon between 4 and 12 days in 2012 and 2014, respectively, while for the Merlot wines from the 2014 harvest, this value was 7 days.

Volatiles Compounds and Their Correlation

Volatile compounds, such as furanones, lactones, and ketones, exhibited a high correlation with the perceived intensity of candied fruit aroma in young wine. Moreover, the highest concentrations of γ-nonalactone, 3-methyl-2,4-nonanedione, masoya lactone, and furaneol were found in Merlot wines made from late-harvested grapes. At the observed concentrations, these compounds can explain the candied fruit aroma detected in red wines. Similar results were obtained for Cabernet-Sauvignon wines made from late-harvested grapes.

This study suggests that volatile compounds produced by the lipoxygenase pathway in grapes might be implicated in the evolution of red wine aroma from sequential harvest dates, offering the possibility of managing organoleptic profiles through harvest date decision-making.

Implications of the Study

Therefore, the results of this study indicate that the late harvest of Merlot and Cabernet-Sauvignon can induce a significant change in wine aroma, without evident changes in the must aroma. This demonstrates that it is challenging to accurately predict wine aroma by sensory evaluation of must aroma. Additionally, this study shows that a small delay in harvest can induce a significant modification of must sugar concentrations and increase the intensity of candied or dried fruit aromas. The molecular basis for these modifications is the greater impact of aromatic compounds in the must and wine, such as furaneol, MND, (Z)-1,5-octadien-3-one, masoya lactone, and γ-nonalactone.

On the other hand, according to previous research on the impact of alcoholic fermentation on the formation of these compounds, it seems that yeast metabolism plays a crucial role in revealing the combined volatile fraction that occurs in grapes when harvested late.

The study warns that further research is needed to determine whether the observations on the evolution of these aromatic compounds are applicable to varieties cultivated in different climatic conditions. However, these results can help the wine industry develop tools to prevent candied or dried fruit aromas in wines, which are increasingly common in the context of climate change.