# Investigation of a Precise Control Scheme for Rice Quality
## 3 Results and Discussion
### Milling Quality  
#### 3.2.1 Additional Crack Percentage  
Rice cracking is a crucial indicator for assessing the quality of rice drying. Figure 7 illustrates the varying degrees of fissures present in rice kernels. The formation of cracks during the drying process was determined based on the ACP, with values ranging from 0.31% to 5.79%. Specific figures can be found in Table 2. All five factors demonstrate highly significant model terms (\(p\) < 0.01), as presented in Table 4. The ACP analysis depicts that the drying temperature and tempering ratio are the primary contributors, accounting for 50.92% and 35.02% in the variance, respectively, as illustrated in Figure 2c. At a significance level of \(p\) < 0.05, the interaction terms T*MC, RH*MC, and RH*TR, as well as the quadratic terms T\({}^{2}\), MC\({}^{2}\), V\({}^{2}\), and RT\({}^{2}\) were found to be statistically significant. The ACP regression equations were derived by eliminating non-significant interactions and quadratic terms  
Figure 5: Interaction effects of T and MC on Dtt: (**a**) 3D surface and (**b**) contour.  
Figure 6: Interaction effects of T and TR on Dtt: (**a**) 3D surface and (**b**) contour.  
(see Table 3). With an R\({}^{2}\) value of 0.9819 and a CV value of 6.76, the model demonstrates excellent fitting ability and reliability.  
To investigate the interaction between the factors, response surfaces and contour plots were generated. Figures 8-10 depict four terms (T, RH, MC, and TR) that exhibit significant interaction effects on ACP. As illustrated in Figure 8a, an increase in drying temperature and initial moisture content results in a notable enhancement in ACP. As depicted in Figure 8b, the contour density along the drying temperature (T) direction exceeds that of the initial moisture content (MC) direction. This phenomenon suggests that an increase in ACP is more responsive to drying temperature, which is consistent with the previous F-value results. Within the temperatures' range of 47 \({}^{\circ}\)C to 55 \({}^{\circ}\)C, the contour lines become denser and the ACP changes dramatically. At higher temperatures, the ACP was found to be more sensitive to temperature. As depicted in Figure 8a, the ACP exhibits a positive correlation with relative humidity when the initial MC values are high (MC \(\geq\) 26% w.b.), whereas at lower MC levels (<26%), an increase in relative humidity leads to a decrease in ACP, particularly at low initial moisture content levels. This observation is also supported by the density of the contour lines shown in Figure 9b. The ACP exhibits a minimum value at 50% relative humidity and an initial moisture content of 20%. As depicted in Figure 10, the larger the tempering ratio and relative humidity, the smaller the ACP becomes. However, at low levels of tempering ratio, the impact of relative humidity on the results is insignificant.  
Figure 8: Interaction effects of MC and T on ACP: (**a**) 3D surface and (**b**) contour.  
Figure 7: Comparison of different types of dried rice kernel (after hulling): (**a**) a whole rice kernel, (**b**) a rice kernel exhibiting a distinct fissure, and (**c**) a partially formed rice grain.