# Effect of Chitosan on the Removal of Different Types of Tannins from Red Wines
## 3 Results and Discussion
### Impact of C and Oxidative Stress on the Reactivity of Wines towards Saliva  
The SPI (saliva precipitation index) was performed to evaluate the reactivity of the wines towards salivary proteins, representing an indirect method to measure wine astringency [34] before and after the treatment with C. According to the ANOVA analysis (\(p\) = 0.005) that considered the effect of C on SPI, the C highly influenced the precipitation of salivary proteins, resulting in a possible decrease in the astringency in control wine and wine treated with condensed tannins (Figure 3).  
This result was also observed in a previous work in which the treatments with C at different phases of winemaking significantly reduced the precipitation of polymeric tannins reactive to BSA [14]. The most astringent wine was GTo, confirming that the addition of gallotannins can influence the astringency negatively [33]. Even with the addition of CTo tannin (condensed tannin), the wine may result more reactive towards salivary proteins and likely astringent. However, the chitosan treatment decreased the SPI values in a significant way, and the percentage decrease was higher in CT-Co (\(-23\%\)) than in the other treated wines. The chitosan probably showed a higher affinity for condensed tannins, allowing more precipitation of the formed complexes with salivary proteins [41]. The control wine Wo did not differ from the wine added with ET tannin (ellagitannin), and after the treatment W-Co and ET-Co were less astringent, similar also to CT-Co.  
\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**} \\  & **(mg/L)** & & **(420 nm + 520 nm + 620 nm)** & & **(420 nm/520 nm)** \\ \hline Wo & 114.49 \(\pm\) 2.11 & * C \(\beta\) & 3.01 \(\pm\) 0.16 & * A \(\beta\) & 0.73 \(\pm\) 0.01 & * B a \\ W-Co & 104.63 \(\pm\) 0.56 & b \(\beta\) & 2.62 \(\pm\) 0.13 & ab \(\beta\) & 0.75 \(\pm\) 0.00 & a a a \\ CTo & 123.16 \(\pm\) 2.04 & * A \(\beta\) & 2.99 \(\pm\) 0.21 & A \(\beta\) & 0.74 \(\pm\) 0.00 & AB a \\ CT-Co & 110.74 \(\pm\) 1.74 & a \(\beta\) & 2.64 \(\pm\) 0.17 & a \(\beta\) & 0.74 \(\pm\) 0.00 & a a a \\ ETo & 119.56 \(\pm\) 1.28 & * AB \(\beta\) & 2.83 \(\pm\) 0.12 & * A \(\beta\) & 0.73 \(\pm\) 0.01 & * B a \\ ET-Co & 94.26 \(\pm\) 1.67 & c \(\beta\) & 2.27 \(\pm\) 0.20 & b \(\beta\) & 0.77 \(\pm\) 0.01 & a a a \\ GTo & 118.09 \(\pm\) 0.88 & * BC \(\beta\) & 2.91 \(\pm\) 0.11 & * A \(\beta\) & 0.79 \(\pm\) 0.06 & A a a \\ GT-Co & 95.81 \(\pm\) 2.08 & c \(\beta\) & 2.64 \(\pm\) 0.15 & a \(\beta\) & 0.78 \(\pm\) 0.00 & a a 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 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.  
\end{table}
Table 7: Oxidation effect on total anthocyanins, colour intensity, and tonality of treated wines.