# Study of the Targeted Regulation of Rice Drying Characteristics and Quality
## 3 Results and Discussion
### Evaluation of Regression Model and Analysis of Variance
#### 3.2.2 Processing Quality  
(1) Effects of test factors on ACP  
The increase rate of burst waist is the change rate of burst waist after reaction drying and before drying, which is an important indicator for evaluating rice quality after drying. As shown in Figure 2c, the order of factors affecting HRV was V \(>\) T \(>\) TR \(>\) MC \(>\) RH, and V had the greatest impact on ACP, followed by hot air temperature. The ACP regression equation is shown in Table 4. R2 of the model was 0.9631, and the CV value was 3.33%, indicating that the model had good fitting ability and reliability. The steeper the surface, the greater the impact of the reaction interaction on the response value. Figure 4a shows the obvious interaction between V, T, and TR, which is consistent with the results of the contribution rate plotted by the F value in Figure 2b. As shown in Figure 5a, the increase rate of burst waist was greatly affected by hot air temperature at low air speed, while at a high air speed, the increase rate of burst waist was not obviously affected by hot air temperature, and the increase rate of burst waist was the lowest at a high air speed. At a high air speed, the air flow was more intense, the residence time of the hot air temperature was reduced, and the rice surface was heated unevenly, which may lead to the insignificant effect of burst waist on hot air temperature. Moreover, when the air speed is too low, the rice is in a glassy state with high hardness and elastic modulus, and internal stress exceeding its own hardness is generated due to the existence of an internal moisture gradient, which also makes the rice extremely susceptible to burst waist [23; 26].  
As shown in Figure 5b,c, when the slow-softening ratio was low but the air speed was high, a large moisture gradient formed inside the rice, leading to further expansion of the glass transition temperature difference between the inner and outer layers and further increasing the expansion coefficient and stress difference between the inner and outer layers. When the stress was greater than the strength of rice, the cracking rate increased. As shown in Figure 5c, the slow-softening ratio was low, and the high-temperature area showed that the increase rate of waist burst decreased. This is because the evaporation rates of water on the surface and inside of rice are relatively consistent, reducing the uneven internal stress and the gap between inner and outer moisture, making overall drying more uniform,which is consistent with the research results of [PERSON] [27] and [PERSON] [28] et al. However, when the slow-softening ratio was high, as shown in Figure 4c, the temperature had little effect on the waist burst rate, which inhibited waist burst. However, slow-softening for too long reduced the drying efficiency of rice.
2. Influence of test factors on HRY Homogeneous rice yield (HRY) is a direct indicator of rice quality, which plays a key role in rice grading and drying quality evaluation [29]. Figure 2d shows the contribution rate. The order of factors affecting HRY was RH > MC > RH > T > V. RH had the greatest impact on HRY, followed by MC and RH. The HRY regression equation is shown in Table 4. R\({}^{2}\) of the model was 0.8977, with a CV value of 0.35%. The model had good fitting ability and reliability.  
As shown in Figure 6a-c, when the humidity changed within the range of 38-50 \({}^{\circ}\)C, HRY changed more drastically, indicating that ACP was more susceptible to humidity changes at higher humidity levels. Appropriate drying humidity helps control the balance of internal and external moisture in rice [23].