# Effect of Chitosan on the Removal of Different Types of Tannins from Red Wines
## 3 Results and Discussion
### Forced Oxidation Trial
As expected, after oxidation total individual anthocyanins dramatically decreased while polymeric pigments and acetaldehyde increased (Table 5). The highest increase in polymeric pigments was detected for CT as already observed in a comparative experiment performed on red wines added with the same kind of tannins [37]. The effect of C on the content of polymeric pigments was higher than those observed before oxidation (between 10.02% and 19.70%). This is not surprising because, as observed for BSA reactive tannins, in this case it is also possible that the removal of molecules with a molecular size ranging from trimer to octamer, showed to be more reactive to BSA, is favoured. It is interesting to observe that the additions of C positively impacted the final concentrations of acetaldehyde in all treated wine. The best effect was observed for the combination of GT and C. In a previous study [11], the authors showed that C operates against oxidation by means of a direct radical scavenging mechanism, however, it can also act indirectly, via metal chelation [48], which would block the generation of radical species following the Fenton reaction [9; 10; 49]. However, it should also be considered that part of acetaldehyde may have been involved in the formation of ethyl-bridged anthocyanins and flavanols [50; 51]. Concerning total individual anthocyanins, the presence of C did not influence the final concentration in wines, except for the ET-C and GT-C samples, while the effect on each individual anthocyanins was significant in few cases: delphinidin 3-glucoside in GT-C, petunidin 3-glucoside in W-C, malvidin 3-glucoside in ET-C, and malvidin 3-(6 II-acetyl)-glucoside in W-C and ET-C (Table 6). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Total Native Anthocyanins**} & \multicolumn{2}{c}{**Polymeric Pigments**} & \multicolumn{2}{c}{**Acetaldehyde**} \\  & **(mg/L)** & & **(mg/L)** & & **(mg/L)** \\ \hline Wo & 58.10 \(\pm\) 4.02 & A \(\beta\) & 367.88 \(\pm\) 13.67 & * C a & 66.10 \(\pm\) 0.30 & * A a \\ W-Co & 46.77 \(\pm\) 6.66 & a \(\beta\) & 331.01 \(\pm\) 5.39 & b a & 62.76 \(\pm\) 0.34 & a a a \\ Cto & 50.62 \(\pm\) 7.99 & A \(\beta\) & 507.34 \(\pm\) 12.28 & * A a & 64.27 \(\pm\) 0.13 & * C a \\ CT-Co & 46.39 \(\pm\) 2.27 & ab \(\beta\) & 418.53 \(\pm\) 15.84 & a a a & 60.74 \(\pm\) 0.13 & b a \\ ETo & 49.74 \(\pm\) 0.23 & * A \(\beta\) & 330.24 \(\pm\) 2.02 & * D a & 64.69 \(\pm\) 0.30 & * C a \\ ET-Co & 38.78 \(\pm\) 0.67 & b \(\beta\) & 265.16 \(\pm\) 2.18 & c a & 58.47 \(\pm\) 0.57 & d a \\ GTo & 46.33 \(\pm\) 6.67 & * A \(\beta\) & 416.83 \(\pm\) 4.08 & * B a & 65.42 \(\pm\) 0.15 & * B a \\ GT-Co & 41.33 \(\pm\) 1.18 & ab \(\beta\) & 337.17 \(\pm\) 8.56 & b a & 59.71 \(\pm\) 0.12 & c a \\ \hline \hline \end{tabular} Different letters indicate a statistically significant difference among treated wines according to Tukey’s (HSD) analysis (\(p<0.05\)). The effect of tannins addition is expressed with a capital letter on wines Wo, Cto, ETo, and GTo (A, B, C,D). The effect of chitosan addition is expressed with a lowercase letter on wines W-Co, CT-Co, ET-Co, and GT-Co (a, b, c, d). The asterisk (*) indicates a statistical difference between each kind of wine before and after the treatment with chitosan. The Greek symbol (a) is used if the value is significantly higher than the non-oxidized sample, and the symbol (\(\beta\)) is used if the value is significantly lower than the non-oxidized sample. All data are expressed as means \(\pm\) standard deviation.  
\end{table} 
Table 5: Oxidation effect on acetaldehyde, total anthocyanins, native anthocyanins, and polymeric pigments of treated wines.