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Study in collaboration with
the University of Turin

THE IMPACT OF OENOLOGICAL TANNINS ON WINE

PHENOLIC, ANTIOXIDANT AND SENSORY CHARACTERISTICS

Oenological tannins are adjuvants that can be used at different stages of production with the aim of increasing the antioxidant capacity and promoting the color stability of must and wine.

The effectiveness of adding tannins in winemaking is related to the botanical origin of the formulation, the chemical characteristics, the polyphenolic content, and the phase and dose of addition.

The hydrolysable tannins, on the other hand, are usually classified into gallotannins and ellagitannins. Gallotannins are present in nuts of plant origin and are gallic acid and D-glucose, with a different degree of substitution with the gallic fraction.
In contrast, ellagitannins consist of D-glucose and ellagic, gallic acids. They are commonly extracted from chestnut and oak and the eight most common forms are monomers, i.e. castalagin, vescalagin, grandinin, and dimers, i.e. roburin A, B, C, D.

To better estimate the antioxidant capacity of the different tannins, the antioxidant power (AP) of each sample was calculated as the antioxidant capacity over the total phenolic concentration measured by the Folin-Ciocalteu (FC) method (see Table 3). This standardisation can be useful to understand how some classes of tannins are more antioxidant than others.

Table 1
Oenological tannins under study.

 

Sample Group Type Description
Sd1 Proc/prod pure Proanthocyanidins from grape seeds Vitis vinifera L.
Sd2 Proc/prod pure Proanthocyanidins from grape seeds Vitis vinifera L.
Sk1 Proc/prod pure Proanthocyanidins from white grape seeds Vitis vinifera L.
Q1 Prof/pror pure Proanthocyanidins from quebracho
Q2 Prof/pror pure Proanthocyanidins from quebracho
Ac Prof/pror pure Proanthocyanidins from Mimosaceae
Et1 Hydro pure Ellagitannins
Et2 Hydro pure Ellagitannins from Quercus spp
Gt Hydro pure Gallotannins from Robina pseudoacacia galls
Mx1 Mix mix Proanthocyanidins from grape skin, quebracho, ellagitannins from Quercus spp
Mx2 Mix mix Proanthocyanidins and ellagitannins
Mx3 Mix mix Proanthocyanidins from grape skins Vitis vinifera L.and quebracho
Mx4 Mix mix Proanthocyanidins from grape skins and seeds of Vitis vinifera L. and quebracho
Mx5 Mix mix Proanthocyanidins from grape skins and seeds of Vitis vinifera L. and quebracho
Mx6 Mix mix Ellagitannins, gallotannins, and proanthocyanidins
Mx7 Mix mix Ellagitannins and proanthocyanidins
Mx8 Mix mix Ellagitannins and proanthocyanidins

Proc/prod = procyanidins/prodelphinidins; Prof/Pror = profisetinidins/prorobinetinidins;
Hydro = hydrolizable tannins, and Mix = mixed formulation.

THUS, FOR THE FIRST TIME, THE MOST SUITABLE OENOLOGICAL TANNINS HAVE BEEN DEFINED FOR DIFFERENT OENOLOGICAL APPLICATIONS. THEIR CONTRIBUTION TO WINE QUALITY IS LINKED TO THEIR ROLE IN THE AROMA AND LONGEVITY OF WINE.

Table 2
Polyphenolic characterisation of the formulations under study.

 

Sample Group Type IPT (gallic acid/100g) FC (gallic acid/100g) BS (cyanidin g/100g) MTC (gallic acid/100g)
Sd1 Proc/prod pure 48.7+-5.7 89.8+-4.2 116.4+-5.7 36.5+-1.7
Sd2 Proc/prod pure 28.7+-3.8 53.3+-2.2 71.3+-3.8 16.7+-3.0
Sk1 Proc/prod pure 21.9+-1.5 33.1+-2.2 33.9+-1.5 6.0+-0.2
Q1 Prof/pror pure 41.0+-0.9 77.0+-5.5 26.9+-0.9 19.7+-13.5
Q2 Prof/pror pure 36.3+-2.1 64.4+-4.9 18.6+-2.1 27.8+-0.9
Ac Prof/pror pure 32.9+-1.7 54.4+-3.5 26.2+-1.7 22.0+-3.4
Et1 Hydro pure 44.8+-2.0 52.2+-2.6   21.0+-7.3
Et2 Hydro pure 37.5+-1.1 52.7+-4.1   19.1+-2.7
Gt Hydro pure 128.2+-4.6 101.4+-4.1   110.4+-1.2
Mx1 Mix mix 39.1+-0.9 62.8+-4.2 25.9+-0.9 29.1+-1.4
Mx2 Mix mix 36.6+-1.7 58.8+-2.9 14.9+-1.7 25.8+-2.9
Mx3 Mix mix 36.8+-0.5 59.6+-4.0 23.8+-0.5 23.4+-3.2
Mx4 Mix mix 32.9+-1.8 51.4+-2.0 22.2+-1.8 15.4+-5.7
Mx5 Mix mix 32.2+-0.6 51.4+-1.0 20.9+-0.6 16.5+-7.3
Mx6 Mix mix 35.2+-1.5 52.9+-1.4 10.6+-1.5 29.2+-0.8
Mx7 Mix mix 28.2+-2.9 55.8+-2.6 20.8+-2.9 25.7+-0.6
Mx8 Mix mix 34.0+-2.0 51.1+-4.8 5.9+-2.0 26.0+-0.8

Data are expressed as average value ± standard deviation.
FC = Folin-Ciocalteu method; BS = Bate-Smith method, MTC = Methylcellulose method.

Table 3
Antioxidant potency (AP) calculated as antioxidant capacity over total phenolic concentration.

 

Sample Group Type ABTS AP ± SD DPPH AP ± SD FRAP AP ± SD CUPRAC AP ± SD
Sd1 Proc/prod pure 5.04 ± 0.23 3.43 ± 0.20 5.33 ± 0.23 8.66 ± 0.61
Sd2 Proc/prod pure 6.95 ± 0.24 4.83 ± 0.23 8.53 ± 0.42 10.96 ± 0.15
Sk1 Proc/prod pure 6.11 ± 0.29 4.19 ± 0.13 6.21 ± 0.17 8.59 ± 0.59
Q1 Prof/pror pure 5.22 ± 0.34 3.60 ± 0.32 4.39 ± 0.31 9.41 ± 0.66
Q2 Prof/pror pure 5.23 ± 0.38 3.63 ± 0.26 5.56 ± 0.42 8.64 ± 0.99
Ac Prof/pror pure 7.41 ± 0.45 5.17 ± 0.39 6.87 ± 0.29 11.20 ± 0.93
Et1 Hydro pure 9.51 ± 0.50 7.73 ± 0.41 10.58 ± 0.57 13.59 ± 0.85
Et2 Hydro pure 8.39 ± 0.71 6.89 ± 0.54 9.04 ± 0.55 11.28 ± 0.86
Gt Hydro pure 7.49 ± 0.30 7.51 ± 0.30 4.69 ± 0.17 11.94 ± 0.45
Mx1 Mix mix 6.02 ± 0.42 4.31 ± 0.31 6.66 ± 0.49 9.83 ± 0.42
Mx2 Mix mix 5.68 ± 0.24 4.22 ± 0.26 6.11 ± 0.39 6.11 ± 0.30
Mx3 Mix mix 5.63 ± 0.38 4.09 ± 0.29 6.14 ± 0.45 9.43 ± 0.76
Mx4 Mix mix 6.83 ± 0.35 4.98 ± 0.15 7.54 ± 0.44 10.14 ± 0.23
Mx5 Mix mix 6.91 ± 0.15 5.02 ± 0.08 7.62 ± 0.21 9.91 ± 1.51
Mx6 Mix mix 6.15 ± 0.14 4.67 ± 0.12 5.80 ± 0.07 10.24 ± 0.60
Mx7 Mix mix 6.14 ± 0.26 4.40 ± 0.20 5.58 ± 0.12 9.88 ± 0.57
Mx8 Mix mix 7.28 ± 0.76 5.57 ± 0.51 7.53 ± 0.61 11.09 ± 1.08

Data are expressed as average value ± standard deviation.

THE RESULTS OF THE STUDY