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

Onofrio Corona,Luciano Cinquanta,Diego De Filippi,Paola Bambina

doi:10.1007/s00217-020-03668-9

Onofrio Corona, Luciano Cinquanta + Show 2 more

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https://doi.org/10.1007/s00217-020-03668-9

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Abstract

In this research, the chemical characterization of fixed and volatile compounds of two different tannins in aqueous solution (Pratiko® 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.

Highlights

Oenological tannins are complex polyphenolic compounds synthesised from a wide range of plant species organs [1], including chestnut, oak and exotic wood, grape skin and seeds and pathogen-induced galls
Grape skin tannins are composed of procyanidins and prodelphinidins with high degree of polymerization (DP) and low level of galloylation, whereas grape-seed tannins are composed only of procyanidins, with a lower DP and a higher level of galloylation [10]
The analytical determination of aqueous solution tannins extracted from oak wood revealed significant differences in the total colloids, resulting from the de-polymerization of wood polysaccharides, in the polyphenols content and in ellagitannins

Summary

Introduction

Oenological tannins are complex polyphenolic compounds synthesised from a wide range of plant species organs [1], including chestnut, oak and exotic wood, grape skin and seeds and pathogen-induced galls. Called proanthocyanidins (with reference to the red colour that develops after treatment with diluted acid), are a group of important secondary metabolites [11], deriving from the oligomerization and polymerization of monomeric units of polyhydroxyl flavan-3-ol, bound by C4-C8 and C4-C6 acid-labels (type B proanthocyanidins) [12, 13], or by an additional C2-O-C7 or C2-O-C5 (type A proanthocyanidins) bond [14, 15]. Hydrolysable tannins are heterosidic phenolic compounds, deriving from esterification between β-Dglucopyranose hydroxyl groups with either gallic acid or hexahydroxydiphenic acid [8, 16, 17].

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