## 4 Conclusions  
This study used the Design Expert software to establish a regression mathematical model to fit the relationships between five drying process parameters (hot-air temperature, humidity, initial moisture content, wind speed and resting time ratio) and drying heat accumulation and key nutrient indicators (protein, fat and starch content). The variance analysis results of the model showed that the R\({}^{2}\) values of all models were above 0.89 and had significant statistical significance (\(p\leq 0.05\)). The study used response surface analysis to investigate the influence of multiple factors on the nutritional quality of rice during drying. The findings showed that the interaction effect between initial moisture content and wind speed was significant, and an increase in wind speed may exacerbate protein oxidation and cause a decrease in protein content. Under high-temperature and high-humidity conditions, fat content decreased, which may be due to increased fat hydrolysis and oxidation. Low temperature and high humidity are conducive to the formation of linear starch, while high humidity conditions inhibit its formation. The interaction effect of humidity and temperature significantly affects the content of branched starch, and the highest content of branched starch is observed under low-temperature and low-humidity conditions, which may be related to the reduction in activity of starch synthesis enzymes. Through a central composite experimental design, the optimal drying process parameters were optimized: hot-air temperature 48.871 \({}^{\circ}\)C, humidity 30.120%, initial moisture content 21.312%, wind speed 0.621 m/s and resting time ratio 2.867. Under these optimized conditions, the total  
Figure 7: AT–PC process reference diagram. Note: (**a**) shows the temper ratio of 2, (**b**) shows the temper ratio of 3 process production diagram.  
drying time was 4.232 h; the effective heat accumulation was 214.442 \({}^{\circ}\)C-h; and the main nutrient components (protein content 8.466 g/100 g, fat content 1.968 g/100 g, linear starch 15.334 g/100 g and branched starch 60.498 g/100 g) all met the expected values. The error rate of the validation experiment was 4.17%, which proved the effectiveness and reliability of the optimization scheme. Furthermore, this study innovatively proposed the effective heat accumulation as a reference index for optimizing drying time. At the same time, it provides theoretical support for understanding the mechanism of rice quality change during rice drying.  
Conceptualization, J.L., Y.J. and W.W.; methodology, J.Y.; software, Y.J.; validation, X.Y., J.L. and Y.J.; formal analysis, Z.Z.; investigation, Y.H.; resources, Q.Y.; data curation, Z.T.; writing--original draft preparation, J.L., Z.Z., Y.H., Q.Y. and Z.T.; writing--review and editing, J.L., K.C., Y.J., X.Y. and X.L.; visualization, J.L.; supervision, Y.J., W.W. and X.Y.; Funding acquisition, Y.J.; Project administration, Y.J. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Academy of National Food and Strategic Reserves Administration, grant number JY2303; National Natural Science Foundation of China (NSFC), grant number 3216150251 and Academy of National Food and Strategic Reserves Administration, grant number H23099.  
Not applicable.  
Data Availability Statement: Data is contained within the article.  
We express our gratitude to the reviewers for their invaluable guidance on this article.  
The authors declare no conflicts of interest.
Figure 17: _Cont_.