# Effect of Chitosan on the Removal of Different Types of Tannins from Red Wines
## 3 Results and Discussion
### Forced Oxidation Trial  
Several studies showed the antioxidant activities of tannins [47] and chitosan, but no study addresses the effect of both treatments on the main phenolic parameters of red wines after an exposure at controlled amounts of oxygen. To obtain this information, all experimental wines underwent a controlled oxidative stress [26]. A significant variation in the reactivity of tannins after oxidation was detected (Figure 2). For all wines, the BSA reactive tannins increased (Figure 2B) and for W-Co, CT-Co, ET-Co, and GT-Co a decrease in VRF occurred (Figure 2C). Data on total phenols did not follow \begin{table}
\begin{tabular}{c c c} \hline \hline  & \multicolumn{2}{c}{\(\Delta\)E} \\ \hline W-WC & 1.99 \(\pm\) 0.59 & b \\ CT-CT C & 2.73 \(\pm\) 0.73 & b \\ ET-ET C & 4.37 \(\pm\) 0.54 & a \\ GT-GT C & 2.81 \(\pm\) 0.89 & b \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Effect of C on \(\Delta\)E calculated between samples treated with C and related controls. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Total Anthocyanins**} & \multicolumn{2}{c}{**Colour Intensity**} & \multicolumn{2}{c}{**Tonality**} \\  & \multicolumn{2}{c}{**(mg/L)**} & \multicolumn{2}{c}{**(420 nm + 520 nm + 620 nm + bins units)**} & \multicolumn{2}{c}{**(420 nm/520 nm)**} \\ \hline W & 301.32 \(\pm\) 2.77 & * AB & 4.11 \(\pm\) 0.10 & * B & 0.54 \(\pm\) 0.01 & B \\ W-C & 288.90 \(\pm\) 3.00 & a & 3.83 \(\pm\) 0.07 & c & 0.53 \(\pm\) 0.00 & a \\ CT & 308.01 \(\pm\) 4.38 & * A & 4.38 \(\pm\) 0.27 & * A & 0.61 \(\pm\) 0.05 & * A \\ CT-C & 292.13 \(\pm\) 1.91 & a & 3.96 \(\pm\) 0.03 & ab & 0.56 \(\pm\) 0.00 & a \\ ET & 307.79 \(\pm\) 5.20 & * A & 4.25 \(\pm\) 0.03 & * AB & 0.57 \(\pm\) 0.00 & *AB \\ ET-C & 289.63 \(\pm\) 2.37 & a & 4.02 \(\pm\) 0.17 & a & 0.53 \(\pm\) 0.02 & a \\ GT & 298.01 \(\pm\) 1.56 & * B & 4.19 \(\pm\) 0.08 & * B & 0.53 \(\pm\) 0.00 & * B \\ GT-C & 285.96 \(\pm\) 4.37 & a & 3.87 \(\pm\) 0.06 & bc & 0.53 \(\pm\) 0.00 & a \\ \hline \hline \end{tabular} Different letters indicate a statistically significant difference among treated wines according to [PERSON]’s (HSD) analysis (\(p<0.05\)). The effect of tannins addition is expressed with a capital letter on wines W, CT, ET, and GT (A, B), and the effect of chitosan addition is expressed with a lowercase letter on wines W-C, CT-C, ET-C, and GT-C (a, b, c). The asterisk (*) indicates a statistical difference between each kind of wine before and after the treatment with chitosan. All data are expressed as means \(\pm\) standard deviation.  
\end{table} 
Table 3: Effect of tannins and C on total anthocyanins, colour intensity, and tonality (evaluated by using spectrophotometric methods). a clear trend, which can be justified considering all factors influencing the formation of coloured complexes among phenolic structures and iron chloride used for this assay [36]. Concerning the treatment with C, data highlighted that, after oxidation, the effect of this treatment on BSA reactive tannins and VRF is still evident but less enhanced. Figure 2: Oxidation effect on total phenols (**A**), tannins reactive to BSA (**B**), and vanillin reactive flavans (**C**) of treated wines. Different letters indicate a statistically significant difference among treated wines according to [PERSON]’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), and 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). 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.