3. Optimised cork powder (CKP) as a wine fining agent to remove negative volatile phenols in contaminated red wine

The air removal of the cork powder cell structure and simultaneous impregnation with ethanol with or without previous removal of cork extractives increased significantly the 4-ethylphenol and 4-ethylguaiacol adsorption performance (Table 2).

Although a significant removal of wine VPs was observed, the overall quality of the treated wine cannot be accessed only by the decrease in these negative aroma compounds, as the impact on the other wine positive aroma components is important to define the final overall sensory olfactory quality [15, 20, 21, 22, 24]. The red wine colour characteristics are important for consumer acceptance of the treated wine, because there is straight relation between the colour and the wine's phenolic composition, namely anthocyanins, whose concentration can be changed by the fining procedure.

In order to have a deeper insight on the impact of optimised cork powder in the wine chemical composition besides the removal efficiency of the VPs, the change in the headspace aroma abundance of wine, phenolic composition and chromatic characteristics were studied and the overall impact on the wine sensory characteristics was evaluated by an expert panel.

#### 3.1 Impact of optimised cork powder on the wine aroma headspace abundance

Air removal and ethanol impregnation of cork samples with and without extractive removal decreased the total headspace aroma abundance (CKNI 32% and CKFI 37%) significantly. The decrease in the particle size of the CKF did not differ significantly on the removal of headspace aroma compounds, although there was an average decrease of 3.7% in relation to CKF (Table 3). The duplication in application dose of CKFI75 resulted in a significant decrease of the total abundance of headspace aroma by more 29% (Table 3). There was a significant correlation (r = 0.731, n = 14, p < 0.003) between the headspace aroma abundance and the octanol-water partition coefficient (log P) of the aroma compounds, strongly


a Values are presented as mean standard deviation; medium spiking levels: 750 μg/L 4-EP and 150 μg/L 4-EG; high 1500 μg/L 4-EP and 300 μg/L 4-EG. Means within a column followed by the same letter are not significantly different ANOVA and Tukey post-hoc test (p < 0.05).

#### Table 2.

irregular occurrence of branching of the main chain does not permit strong intermolecular association by hydrogen bonding; nevertheless, they are extracted using strong alkaline solutions (4–10% w/v NaOH). Pectins also exist in low quan-

Schematic structures of main cork cell wall polysaccharides: (a) cellulose, (b) 4-O-methylglucuronoxylan, (c) arabino-4-O-methylglucuronoxylan and (d) 4-O-methylglucurono-arabinogalactoglucoxylan.

Cork contains 8–20% of low molecular weight compounds including fatty acids, terpenes, long-chain aliphatic compounds and saccharides, collectively known as extractives [34, 46]. Cork contains also about 6% of tannins [36]. The most important of these components are waxes and tannins [31]. Waxes are extracted by low polarity solvents, such as benzene, chloroform, ethyl acetate [47], hexane [36] and ether [26]. The waxes are responsible for the cork impermeability. The waxes extracted were found to consist of two fractions: neutral and acidic. The neutral fraction is mostly composed of fatty alcohols (C18▬C26) with some unsaturated

The acid fraction is essentially composed of fatty acids (C14▬C24) with unsatu-

octadecenoic acids. More or less 50% of the waxes are triterpenes from friedelin and lupine families including friedelin, 3-α-hydroxyfriedelan-2-one, botulin, betulinic acid, β-sitosterol and sitost-4-en-3-one [48]. Cork extractable phenolic compounds include ellagic acid and some quantities of gallic acid, protocatechuic acid/aldehyde, aesculetin, vanillic acid, caffeic acid, vanillin, scopoletin, ferulic acid, coniferyl aldehyde and sinapaldehyde [49, 50]. The extraction of tannins can be done by polar solvents such as water [51] and ethanol [52]. Cork tannins include roburins A and E, grandini, vescalagin and castalagin. The yields of these two components change in function of the nature of the cork (virgin or reproduction) where signif-

rated ω-hydroxyacids, 18-hydroxy-9,12-octadienoic and 18-hydroxy-9-

icant variation is found in the bibliography [1].

tities in cork, approximately 1.5%, placed in the middle lamella [45].

2.4 Extractable components

Advances in Grape and Wine Biotechnology

Figure 5.

groups and triterpenes.

234

Amount of 4-EP and 4-EG (μg/L) removed from wines at two spiked levels<sup>a</sup> of natural cork powder (CKN) and dichloromethane and ethanol extractive free cork powder (CKF) before and after air removal and impregnation with ethanol (CKNI and CKNFI) [10].


 3. Headspace

and ethanol extractive free cork after air removal and ethanol

(CKF75250

 and

CKFI75500).

 aroma profile of red wines before (VP-free T0 and VP-spiked with 750 μg/L of 4-EP and 150 μg/L of 4-EG, TF) and after treatment with natural cork and

impregnation

 (CKNI and CKFI) and cork powders with a particle size below 75 μm at two application

dichloromethane

 doses (250 and 500 g/hL) suggesting that the interaction of the volatile compounds including the VPs with the cork powder is of hydrophobic nature as observed for the interaction of other molecules with cork [7, 53, 54]. When compared to activated carbons applied at 100 g/hL, CKFI75250 (250 g/hL) showed a lower impact on the headspace aroma abundance (40 vs. 75%) and even CKFI75500 (500 g/hL) resulted in a lower reduction of 69%. Therefore, cork powder decreased the wine headspace aroma

Air Depleted and Solvent Impregnated Cork Powder as a New Natural and Sustainable Wine

3.2 Impact of optimised cork powder on wine chromatic characteristics and

anthocyanins that generally did not change by the use of all cork powders (Table 5). For the individual phenolic acids overall, their levels did not change significantly, or their decrease was significant but small, and these decreases occurred mainly for the CKFI75 at the two application doses (decreased for trans

3.3 Impact of optimised cork powder on wine sensory attributes

Application of optimised cork powder results in a decrease of the colour intensity, although being only significantly different from the control for the CKFI and CKFI75500. For the L\* and a\*, the same was observed (Table 4). These variations for the colour intensity are not due to a decrease in the concentration of monomeric

—5.9%; caffeic acid

levels for all cork powders applied. These results show that optimised cork powders, either with or without extractive removal, have a low impact on wine phenolic composition; nevertheless, the ethanol impregnated extractive free corks had a significant impact on wine colour intensity, suggesting that these corks influence wine polymeric pigments as no significant changes on monomeric anthocyanins were observed. The impact for cork powders on wine phenolic composition and colour intensity of wines was lower than that generally observed for activated

To validate the impact of natural and extractive free ethanol impregnated cork powder samples on the headspace VP decrease and its effect on the sensory perception and quality of wines, CKNI, CKFI and CKFI75—treated wines at the two application doses (250 and 500 g/hL, CKFI75250 and CKFI75500, respectively) were subjected to sensory analysis by an expert panel. As expected, the presence of these VPs affect the aroma profile of spiked wine (TF) significantly and negatively (Table 6), by the increase of the phenolic attribute, decreasing the wine fruity and floral attributes significantly [20, 24, 55]. The panel consensus on each wine attribute was accessed through the percentage of variance explained by the first PCA [56] applied to the panel scores for each attribute. The variance explained by PC1

have been reported for trained panels assessing different attributes and different products [20, 24, 62]. Colour intensity, floral, fruity, phenolic, acidity, balance and persistence wine attributes resulted in a consensus among judges (Table 6). For the colour hue, limpidity, oxidised (visual), vegetable, oxidised (aroma) and body, the judges attributed identical scores. There is no consensus on the other sensory wine attributes that could be due to the low difference of the attributes among samples or

changes in motivation, sensitivity and psychological answer behaviour [57].

nificantly lower than T0 and TF, with the increase in the application dose

In accordance with the instrumental colour intensity, sensory colour intensity of the wines treated with ethanol impregnated extractive free cork powders was sig-


…

—12% and

—20%; ferulic acid

C-indexes presented in Table 6. Similar values

—19%) (Table 5). For catechin, there was no change in its

compounds lesser than the activated carbons [21].

DOI: http://dx.doi.org/10.5772/intechopen.85691

—5.6%; coutaric acid

phenolic compounds

caftaric acid

coumaric acid ethyl ester

carbons used at 100 g/hL [20].

ranged from 45 to 87%, yielding the

237

#### Advances in Grape and Wine Biotechnology

Air Depleted and Solvent Impregnated Cork Powder as a New Natural and Sustainable Wine… DOI: http://dx.doi.org/10.5772/intechopen.85691

suggesting that the interaction of the volatile compounds including the VPs with the cork powder is of hydrophobic nature as observed for the interaction of other molecules with cork [7, 53, 54]. When compared to activated carbons applied at 100 g/hL, CKFI75250 (250 g/hL) showed a lower impact on the headspace aroma abundance (40 vs. 75%) and even CKFI75500 (500 g/hL) resulted in a lower reduction of 69%. Therefore, cork powder decreased the wine headspace aroma compounds lesser than the activated carbons [21].
