## 3 Results and Discussion
### Effect of Leading Cycles on WPG  
The effects of the water leaching cycles on the WPG are shown in Figure 4. The WPGs of the four treatments were basically the same after three washing cycles: the water saturation and oven drying caused a minor but steady decrease in the WPG over the three leaching cycles (Figure 4a-d). The rate of decrease in the WPG was more apparent for ZC-103 at high MA concentrations. A decrease in WPG during leaching experiments has also been observed in wood esterified by citric acid [24]  
Figure 3: Weight percent gain (WPG) (**a**) and weight leaching ratio (WLR) (**b**) of wood treated with different methods and concentrations. Error bars represent the standard deviation of 20 replicates per treatment.  
and succininic anhydride [25] and etherified by glutaraldehyde [26]: all compounds provided similar results. The average decreases in the WPG of 103, ZC-103, 120, and ZC-120 were 2.76%, 4.12%, 2.05%, and 3.29%, respectively. After three washing cycles, the WPG of the samples decreased by less than 5%, indicating that after the first leaching test, most of the chemicals that were incorporated and were present on the surface of the samples were washed out, and that in the remaining two washing cycles, the WPG decreased substantially. In general, the average decrease in ZC-103 was slightly higher than in the other groups. One reason may be that the initial presence of the chemicals was larger in ZC-103 than in the other groups. Another reason was that the chemicals were not completely fixed in the cell cavity at 103 \({}^{\circ}\)C, and the addition of ZnCl\({}_{2}\) increased the permeability: therefore, the outflow increased. The average decrease was lowest in 120, indicating that the modifier reacted with the cell wall at 120 \({}^{\circ}\)C and effectively immobilized it in the cell wall and cell cavity. The final WPG results after washing (Table 1) showed that, although the value of ZC-103 was higher than in the other groups, the final result was higher than in the other three treatments at the same MA concentration. It was greater than the amount of loss compared to the amount of fixing. In summary, although the addition of ZnCl\({}_{2}\) increased the loss rate to some extent, the relative loss rate was much smaller than in the other groups, and the samples treated at 120 \({}^{\circ}\)C exhibited stability during the washing cycles; however, the final fixation rate was lower than in the other groups. In addition, the STDVA of the WPG of the samples during the water cycle test was in the range of 0.60-4.47%, indicating that the response of the samples was similar.  
Figure 4: WPG of wood treated with different concentrations of maltodextrin (MA) and different treatments after three water leaching steps. The error bars represent the standard deviation of 20 replicates per treatment. (**a**) WPCs of 103 treatment after three leaching cycles; (**b**) WPCs of ZC-103 treatment after three leaching cycles; (**c**) WPCs of 120 treatment after three leaching cycles; (**d**) WPCs of ZC-120 treatment after three leaching cycles.  
Figure 5 shows the characterization of the immersion liquid after three water leaching cycles. Figure 5a-c shows that as the concentration of MA increased, the liquid became more turbid. The color of 103 treatment was darkest, 120 treatment had the lightest color, and the ZC-103 and ZC-120 treatments were lighter: this was in agreement with the results of the leaching experiment (Figure 3b). The spectrophotometer results in Figure 5d-f indicate that after three water cycles, the absorbance was similar for the groups and increased with the MA concentration. The order in terms of the absorbance was 103 \(>\) ZC-103 \(>\) 120 \(>\) ZC-120. In general, the absorbance decreased significantly between the first cycle and second cycle, but there was no significant change from the second to the third cycle, indicating that after one wash, most of the unreacted modifier was washed out. A visual assessment was consistent with these expectations.