## 2 Results and Discussion
### Effect of Wine Fining Treatments in the Profile of Volatile Organic Compounds
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Peak \#** & **Chemical Family** & **Compound Name** & **LRI Calca** & **LRI Lit** & **\#** & **\(\Delta\) (LRI Calc-LRI Lit)** \\ \hline
6 & Alcohol & 3-Methyl-1-pentan-1-ol & 851 & 843 & 8 \\
9 & Alcohol & 3-Hexen-1-ol (isomer) & 860 & 855 & 5 \\
12 & Alcohol & Hexan-1-ol & 872 & 870 & 2 \\
24 & Alcohol & 2-Ethylhexanol & 1030 & 1029 & 1 \\
25 & Alcohol & Benzyl alcohol & 1033 & 1033 & 0 \\
28 & Alcohol & Octan-1-ol & 1071 & 1078 & \(-\)7 \\
29 & Aldehyde & 4-Methyl benzaldehyde & 1078 & 1079 & \(-\)1 \\
39 & Aldehyde & Decan & 1203 & 1205 & \(-\)2 \\
5 & Alkanes & 2,4-Dimethyl-hept-1-ene & 845 & 842 & 3 \\
33 & Alkanes & Cosmene & 1129 & 1134 & \(-\)5 \\
48 & Alkanes & Tridecane & 1296 & 1300 & \(-\)4 \\
56 & Alkanes & Pentadecane & 1498 & 1500 & \(-\)2 \\
67 & Alkanes & Heptadecane & 1693 & 1700 & \(-\)7 \\
70 & Alkanes & Nonadecane & 1895 & 1900 & \(-\)5 \\
71 & Alkanes & Eicosane & 1995 & 2000 & \(-\)5 \\
10 & Aromatic & Ethylbenzene & 862 & 864 & \(-\)2 \\
11 & Aromatic & Xylene & 869 & 866 & 3 \\
19 & Aromatic & 1,3,5-Trimethyl-benzene & 990 & 995 & \(-\)5 \\
55 & Aromatic & 3-Ethyl-3-phenyl-pent-1-ene & 1477 & & NC \\
1 & Ester & Ethyl acetate & NC & 610 & NC \\
2 & Ester & Ethyl isobutyrate & NC & 756 & NC \\
3 & Ester & Ethyl butanoate & 814 & 806 & 8 \\
4 & Ester & Ethyl lactate & 824 & 815 & 9 \\
7 & Ester & Ethyl 2-methylbutanoate & 856 & 856 & 0 \\
8 & Ester & Ethyl 3-methylbutanoate & 859 & 867 & \(-\)8 \\
13 & Ester & Isoamyl acetate & 880 & 878 & 2 \\
15 & Ester & 1-Ethoxypropan-2-yl acetate & 937 & 965 & \(-\)28 \\
20 & Ester & Ethyl hexanoate & 1000 & 1001 & \(-\)1 \\
22 & Ester & Hexyl acetate & 1014 & 1015 & \(-\)1 \\
31 & Ester & 2-Butoxyethyl acetate & 1093 & 1090 & 3 \\
37 & Ester & Diethyl succinate & 1181 & 1182 & \(-\)1 \\
38 & Ester & Ethyl octanoate & 1196 & 1199 & \(-\)3 \\
43 & Ester & Ethyl phenylacetate & 1242 & 1244 & \(-\)2 \\
44 & Ester & 2-Phenethyl acetate & 1253 & 1257 & \(-\)4 \\
47 & Ester & Ethyl nonanoate & 1293 & 1294 & \(-\)1 \\
50 & Ester & Ethyl decanoate & 1394 & 1397 & \(-\)3 \\
52 & Ester & Ethyl-3-methylbutyl & 1428 & 1433 & \(-\)5 \\  & & butanedoate & 1589 & 1597 & \(-\)8 \\
61 & Ester & Ethyl dodecanoate & 1592 & 1581 & 11 \\  & & 3-propan-2-yl-butanedioate & & & \\
68 & Ester & Ethyl tetradecanoate & 1789 & 1793 & \(-\)4 \\
14 & Ketone & 6-Methyl-2-heptanone & 928 & 932 & \(-\)4 \\
27 & Ketone & 2-Nonanone & 1055 & 1091 & \(-\)36 \\
54 & Ketone & Geranyl acetone & 1451 & 1452 & \(-\)1 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: VOCs tentatively identified in the samples under analysis by GC/TOFMS. Esters were the most abundant group, with 22 compounds. Alcohols and carbonyl compounds were also detected, along with terpenoids and alkanes, as reported elsewhere for Portuguese wines varieties [17; 30; 31; 54; 55]. Considering the extensive chromatographic data generated, a multivariate technique of data analysis was used. Indeed, principal component analysis (PCA) is considered an appropriate statistical method, which allows us to reveal basal data structures when hidden patterns are easier to perceive [17; 30; 31; 56]. In Figures 7-9, one can observe that all the monovarietal wines studied could be identified through their VOC profile when polymer or bentonite was used. For Encruzado (Figure 7), the first and second PCs explained more than 67% of the system variance. The samples treated with bentonite were clearly separated from the samples treated with the polymer through PC2, namely by peaks **1** (ethyl acetate), **20** (ethyl hexanoate), **23** (limonene), **37** (diethyl succinate), **50** (ethyl decanoate), and **57** (2,4-di-tert-butylphenol), whereas the DCMC-treated samples were characterized by peaks **29** (4-methyl benzaldehyde) and **44** (2-phenethyl acetate). The control was separated through peaks **20** (ethyl hexanoate) and **38** (ethyl octanoate) from all other Encruzado samples along PC1.