## 3 Results and Discussion
### Evaluation of Drying Effect Using Water Retention Value and Simons' Staining Method
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**FPU/g-Pulp** & **Never Dried** & **Freeze Dried** & **Oven Dried** &
\begin{tabular}{c} **Oven Dried after 24 h of** \\ **EH with 10 FPU/g-Pulp** \\ \end{tabular} \\ \hline WRV (\%) & 166.1 & 158.4 & 105.7 & 203.0 \\ EH with 4 FPU/g-Pulp & 83.9 \(\pm\) 2.2 & 81.4 \(\pm\) 0.6 & 70.4 \(\pm\) 0.8 & NA \\ EH with 10 FPU/g-Pulp & 96.6 \(\pm\) 0.5 & 96.1 \(\pm\) 0.4 & 88.7 \(\pm\) 0.1 & NA \\ EH with 20 FPU/g-Pulp & 100.7 \(\pm\) 0.9 & 101.0 \(\pm\) 0.2 & 93.2 \(\pm\) 0.4 & NA \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Water retention value (WRV) and enzymatic digestibility depending on drying. cellulose [41]. Thus, enzymatic hydrolysis could be enhanced by increasing the accessibility through pore formation. The drying process decreased enzyme accessibility and reduced enzymatic hydrolysis. This can be explained by using the opposing mechanism of pretreatment on enzyme accessibility and enzymatic hydrolysis. The drying effect was more remarkable at the initial stage and then it decreased as hydrolysis progressed. However, the irreversible change in structure made a difference to the maximum enzymatic digestibility. Evaluation of Drying Effect on Crystalline Structure Using \({}^{13}\)C CPMAS Solid-State NMR Analysis  
The ultrastructure of cellulose has mainly been determined by \({}^{13}\)C CPMAS solid-state NMR spectroscopy [42; 43], and the solid-state NMR characterized changes associated with drying pulp [44] and bleached pulp by hornification has also been reported [19]. The \({}^{13}\)C solid-state NMR analysis was performed in wet conditions for the ND, OD and FD pulps and the spectra with signals assigned are shown in Figure 3[19]. The \({}^{13}\)C NMR spectrum of the pulp was mainly dominated by signals assigned to cellulose. Signals assigned to C-4 and C-6 were partially separated into two clusters, labeled i and s, which were assigned to the interior and surface of the crystalline domains, respectively. Broadening of the NMR signal and relative sharpening of C-4 and C-6 signals on the surfaces of crystalline domains by partial drying has been reported, but the signal broadening and sharpening of C-4 and C-6 signals can be reversed by rewetting the pulp [19]. The \({}^{13}\)C NMR spectra of all three pulps were quite similar because both the FD and OD pulps were analyzed in a wet state. Although it has been reported that several repetitions of drying and rewetting cause the difference to peak at 89.4 ppm due to the irreversible drying effect [19], it was not observed in this study because drying was performed only once and rewetting for NMR analysis might reverse the drying effect. Therefore, it can be concluded that drying once did not cause an irreversible change in crystalline structure, and therefore, the decrease in enzymatic digestibility does not seem to be related to the structure of cellulose. However, it might be related to cellulose structure if the pulp was dried more than once. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Pulps**} & \multicolumn{2}{c}{**Amount of Adsorbed Dye by Simons’ Staining (mg g-1)**} \\ \cline{2-4}  & **Orange Dye** & **Blue Dye** & **Total** \\ \hline Never dried & 154.4 \(\pm\) 2.3 & 36.7 \(\pm\) 2.0 & 191.0 \(\pm\) 4.3 \\ \hline \hline Oven dried & 75.9 \(\pm\) 3.0 & 62.1 \(\pm\) 5.8 & 138.0 \(\pm\) 8.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Amount of adsorbed dye depending on drying methods. Figure 3: 13C solid-state NMR spectra of never-dried, freeze-dried and oven-dried pulps.