Influence of pre-fermentative addition of aqueous solution tannins extracted from oak wood (Quercus petraea) on the composition of Grillo wines

In this research, the chemical characterization of fixed and volatile compounds of two different tannins in aqueous solution (Pratiko (R) L-Harvest and L-Fruit) extracted from oak wood, has been studied. The influence of the above tannins, at different concentrations, on the alcoholic fermentation kinetics and on the composition and sensorial characteristics of a white wine were then evaluated. The wines added tannins in aqueous solution compared to control wines showed significant differences in fixed compounds (colloids, polyphenols and ellagitannins) and volatile compounds (phenolic aldehydes, volatile phenols, furanic and piranic compounds). The differences of aqueous solution tannins extracted from oak wood were partly due to the drying/maturing and roasting methods used in barrel production. Alcoholic fermentation was partially facilitated by the addition of tannins in aqueous solution. The wines obtained showed a higher content of ethyl esters of medium-chain fatty acids (from 22 to 31%) and, in some cases, higher acetate alcohols (from 15 to 28%), relevant to the olfactory sensations provided to the wines. The tannins added to the must before fermentation also made it possible to obtain an additional supply of polyphenols (from 25 to 85%) able to induce more complex sensory profiles in the wines, with increased persistent taste notes.

Automated summary

This research investigated the chemical characterization of two different tannins extracted from oak wood in aqueous solution, as well as their influence on alcoholic fermentation kinetics and sensory characteristics of white wine. The addition of tannins in aqueous solution resulted in significant differences in fixed and volatile compounds of the wines, and facilitated alcoholic fermentation. This study also found that adding tannins before fermentation led to wines with more complex sensory profiles and increased persistent taste notes.