## 3 Results and Discussion
### Color Kinetics of the NR Sheets
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Type of Coagulating** & **Velocity** & **Drying** & **Drying** & **YI Value** & \multicolumn{2}{c}{_YI Value_ Prediction (Order)} \\ \cline{4-7}
**Material** & **(m/s)** & **Temp. (\({}^{\circ}\)C)** & **Time (h)** & **Experiment** & **Zero** & **First** & **Second** \\ \hline PR wood vinegar & 0.3 & 50 & 84 & \(51.2\pm 1.2\)\({}^{\text{b}}\) & 50.3 & 50.7 & 50.3 \\  & & 60 & 60 & \(54.1\pm 0.3\)\({}^{\text{c}}\) & 54.7 & 54.6 & 56.2 \\  & & 70 & 48 & \(62.5\pm 1.2\)\({}^{\text{b}}\) & 59.8 & 61.4 & 68.9 \\  & 0.5 & 50 & 80 & \(52.6\pm 0.8\)\({}^{\text{d}}\) & 52.1 & 53.7 & 55.8 \\  & & 60 & 52 & \(56.8\pm 1.0\)\({}^{\text{d}}\) & 57.3 & 62.1 & 64.5 \\  & & 70 & 42 & \(63.8\pm 0.3\)\({}^{\text{c}}\) & 64.2 & 64.8 & 67.2 \\  & 0.7 & 50 & 75 & \(54.5\pm 0.9\)\({}^{\text{a}}\) & 53.7 & 56.1 & 58.5 \\  & & 60 & 44 & \(57.2\pm 0.3\)\({}^{\text{c}}\) & 57.7 & 58.9 & 59.7 \\  & & 70 & 36 & \(64.9\pm 1.2\)\({}^{\text{b}}\) & 63.7 & 65.8 & 68.5 \\ Bb wood vinegar & 0.3 & 50 & 84 & \(60.5\pm 0.7\)\({}^{\text{e}f}\) & 61.8 & 63.2 & 64.6 \\  & & 60 & 60 & \(61.8\pm 1.0\)\({}^{\text{f}g}\) & 63.1 & 64.6 & 65.9 \\  & & 70 & 48 & \(63.6\pm 0.8\)\({}^{\text{d}}\) & 62.6 & 64.5 & 65.3 \\  & 0.5 & 50 & 80 & \(62.7\pm 1.2\)\({}^{\text{b}}\) & 59.3 & 62.2 & 68.1 \\  & & 60 & 52 & \(62.9\pm 0.8\)\({}^{\text{gh}}\) & 63.5 & 65.1 & 67.8 \\  & & 70 & 42 & \(65.1\pm 1.2\)\({}^{\text{b}}\) & 63.8 & 65.7 & 71.3 \\  & 0.7 & 50 & 75 & \(64.8\pm 1.0\)\({}^{\text{f}g}\) & 63.5 & 68.7 & 73.4 \\  & & 60 & 44 & \(63.4\pm 1.2\)\({}^{\text{b}}\) & 61.2 & 64.6 & 69.2 \\  & & 70 & 36 & \(67.6\pm 1.5\)\({}^{\text{ab}}\) & 62.8 & 67.4 & 72.1 \\ CS wood vinegar & 0.3 & 50 & 84 & \(60.9\pm 0.7\)\({}^{\text{e}f}\) & 62.1 & 63.7 & 65.1 \\  & & 60 & 60 & \(62.8\pm 0.6\)\({}^{\text{d},e}\) & 63.1 & 65.2 & 67.7 \\  & & 70 & 48 & \(64.6\pm 1.2\)\({}^{\text{b}}\) & 62.8 & 69.2 & 71.5 \\  & 0.5 & 50 & 80 & \(61.4\pm 0.8\)\({}^{\text{d}}\) & 60.3 & 62.5 & 64.7 \\  & & 60 & 52 & \(63.5\pm 1.0\)\({}^{\text{f}g}\) & 64.2 & 65.8 & 67.1 \\  & & 70 & 42 & \(65.8\pm 1.0\)\({}^{\text{f}g}\) & 63.9 & 65.5 & 69.2 \\  & 0.7 & 50 & 75 & \(63.1\pm 0.8\)\({}^{\text{d}}\) & 62.8 & 64.7 & 66.3 \\  & & 60 & 44 & \(64.7\pm 1.0\)\({}^{\text{f}g}\) & 64.3 & 67.6 & 72.9 \\  & & 70 & 36 & \(67.1\pm 1.5\)\({}^{\text{a,b}}\) & 62.3 & 66.3 & 71.9 \\ Acetic acid & 0.3 & 50 & 84 & \(51.7\pm 1.2\)\({}^{\text{b}}\) & 50.9 & 51.4 & 50.8 \\  & & 60 & 60 & \(54.5\pm 0.3\)\({}^{\text{c}}\) & 54.2 & 54.8 & 56.7 \\  & & 70 & 48 & \(62.6\pm 0.6\)\({}^{\text{d}}\) & 63.7 & 64.5 & 67.1 \\  & 0.5 & 50 & 80 & \(56.5\pm 0.8\)\({}^{\text{d}}\) & 54.2 & 55.3 & 56.8 \\  & & 60 & 52 & \(57.8\pm 1.0\)\({}^{\text{f}g}\) & 59.2 & 63.7 & 64.9 \\  & & 70 & 42 & \(64.8\pm 1.2\)\({}^{\text{b}}\) & 61.8 & 63.6 & 68.3 \\  & 0.7 & 50 & 75 & \(58.3\pm 1.5\)\({}^{\text{a,b}}\) & 55.3 & 57.2 & 62.5 \\  & & 60 & 44 & \(59.4\pm 0.7\)\({}^{\text{e}f}\) & 60.2 & 64.5 & 66.9 \\  & & 70 & 36 & \(65.2\pm 0.3\)\({}^{\text{c}}\) & 64.9 & 65.8 & 67.7 \\ Reference & & & & \(59.8\pm 0.9\)\({}^{\text{a}}\) & & & \\ \hline \hline \end{tabular} a-h: Different letters in the same column indicate a significant difference at a certain \(p\)-value (\(p<0.05\)).  
\end{table} 
Table 2: The experimental and predictable _YI_ value of the NR sheet samples at the final moisture content and the total drying time (temp. = temperature, PR = para rubber, Bb = bamboo, and CS = coconut shell). For the changed NR sheet, the browning process was categorized into two interactions: non-enzymatic and enzymatic browning. As is known, the sheet color change in the non-enzymatic browning reactions was divided into two interactions: lipid oxidation and the Maillard interaction. For the lipid oxidation process, the NR sheet has unsaturated fatty acid elements. When it is oxidized by the oxygen in the air, the pigments in the sheets change by forming colored polymers [57; 58]. The Maillard reaction occurs as the color value of the product changes during the drying process [58; 59].