## 3 Results
### Response Surface Plot Analysis
exposure to high temperatures could lead to structural changes in proteins and a reduction in their solubility. Based on these research results, we hypothesize that rice--being a similar cereal crop--may experience analogous denaturation phenomena after prolonged exposure to elevated temperatures, resulting in decreased protein solubility. Therefore, high temperatures should be avoided as much as possible during the drying process. Figure 2: Contribution map of factor response indicators. Note: total drying time, Dtt; effective accumulated temperature, AT. The protein content of undried rice was 7.58 g/100 g; fat content was 1.9 g/100 g; amylose AC was 6.62 g/100 g; amylopectin APC was 118.7 g/100 g.  
(2) Response analysis of fat content (FC)  
In the process of drying rice, it is essential to manage the drying conditions effectively to enhance the quality, nutritional content and shelf life of the rice. Environments characterized by high temperatures and humidity can accelerate fat hydrolysis in rice, resulting in the formation of glycerol and free fatty acids. This may also lead to lipid oxidation, producing compounds such as peroxides, aldehydes and ketones. These alterations not only impact the acid value but can also influence the aging processes and flavor characteristics of rice. Specifically, aldehydes generated from lipid oxidation might impair the flavor profile of rice, while free fatty acids arising from hydrolysis could compromise its storage stability and overall eating quality. Based on the F values presented in Table 5 and Figure 2, factors influencing changes in fat content are prioritized as follows: relative humidity (RH) > moisture content (MC) > temperature (T) > wind speed (V) > rotational speed (TR). The regression equation detailing variations in fat volume is provided in Table 3 with a coefficient of determination R\({}^{2}\) at 0.8. During the drying phase, there was a reduction in fat levels within the rice grains. This decrease can be attributed partly to peroxide production along with glycerol and free fatty acids due to fat hydrolysis. Additionally, elevated temperatures facilitate lipid oxidation that leads to an increase in aldehydes and ketones; this effect is particularly pronounced at 37 \({}^{\circ}\)C where fat loss is most notable. Fat enzyme acts as a key hydrolytic enzyme responsible for breaking down fats. As illustrated in Figure 4, there is a gradual decline in fat enzyme activity throughout drying; this trend correlates with rising fatty acid concentrations alongside decreasing pH levels. Higher temperatures further stimulate fatty acid production, which results in lower pH values that inhibit fat enzyme activity [39, 40]. (3) Amylose content response analysis (AC)  
The content of amylose in rice is the key factor affecting the edible and nutritional quality of rice. According to the results in Table 5 and Figure 2, F value reflects the degree of influence of various factors on the response, and it can be seen that the order of factors affecting AC is RH > T > TR > V > MC. The regression equation of protein content is shown in Table 3. The coefficient of determination of the model R\({}^{2}\) is 0.9028 and the value of CV is 11.80%, indicating that the model has good fitting ability and reliability. Figure 3: Interaction effect on the protein content. Note: The redder the response surface graph, the larger the value, and the bluer the value, the smaller. As can be seen from Figure 5, the interaction of temperature and relative humidity during the drying of paddy grains had a significant effect on the content of straight-chain starch within the experimental protocol. Compared with the undried rice grains, the whole straight-chain starch content (soluble and insoluble straight-chain starch content) of the rice grains treated with different drying parameters were increased as a whole; since branched-chain starch would be partially converted into straight-chain starch or other sugars by the drying environment, the content of straight-chain starch would be increased.