The functional compounds of oenological wood

Riccardo Savastano, HTS

Effects of adding oak chips (French and American) and oak tannins in aqueous solution on the composition of wines

Onofrio Corona, University of Palermo

In this work, the effects of using oak chips, French and American oak, and tannins in aqueous solution, extracted from oak wood, on white grape musts and crushed red grape musts were studied. To evaluate the influence, of chips and liquid tannins, on the kinetics of alcoholic fermentation and on the composition and sensory characteristics of white wines and red wines, white grape musts extracted from Grillo grapes (western Sicily), were fermented in the presence of French oak chips (unroasted, I-OAK Expression) and in the presence of tannins in aqueous solution (Pratiko® L-Harvest and L-Fruit), at different concentrations, while crushed red Sangiovese Rubicone grapes (Emilia Romagna), were fermented in the presence of French oak chips (unroasted, I-OAK Expression) and French and American oak chips (medium+ toast, I-OAK Trend).

The wines obtained showed significant differences in volatile and nonvolatile compounds extracted from the chips, both by origin and level of toasting. The alcoholic fermentation of the musts and crushed grapes was partly favored by the presence of the chips and liquid tannins, and the wines obtained, compared with the control wines, showed significant differences in fixed compounds (colloids, polyphenols and ellagitannins) and volatile compounds (ethyl esters of medium-chain fatty acids and acetates of higher alcohols, phenolic aldehydes, volatile phenols, furanic compounds, pyranic compounds).
Chips and tannins added to the must and crushed grapes before alcoholic fermentation also provided an additional supply of polyphenols capable of inducing more complex sensory profiles in the wines, with more persistent flavor notes. In fact, sensory analysis revealed greater complexity, volume, finesse and aromatic persistence of the tests obtained from musts or crushed wines with chips added; moreover, they were preferred to the witness wines in both olfactory and gustatory aspects.

The relationship between wine and wood has deep roots that dig into the history of enology.
The wooden barrel was born from the ingenuity and necessity of man to have to preserve and transport this product in the best possible conditions but today, the stabilizing and improving role of wood towards wines is recognized worldwide. This has also been possible thanks to the evolution of technology and analytical techniques through which numerous researchers have approached this issue and which have enabled them to understand the nature of the wood itself and to isolate specific molecules from it.
Ellagitannins, polysaccharides and aromatics are the functional compounds on which both the properties and applications of oenological wood depend, and in modern oenology, oak chips and tannins in solution are useful technological tools to achieve multiple goals, including: antioxidant protection, color stability, aromatic cleanliness and improved taste sensations.