# Study of the Targeted Regulation of Rice Drying Characteristics and Quality
## 3 Results and Discussion
### Parameter Optimization and Model Validation  
To obtain the optimal combination of slow-drying parameters, the target value of net drying time, waist bursting increase rate, fatty acid value, and fat mass fraction was limited to the minimum, while the whole rice rate, resistant starch concentration, germination rate, and protein mass fraction were maximized. The model was optimized by Design-Expert software, and the optimal combination of process parameters within the test range was obtained as follows: hot air temperature, 43.138 \({}^{\circ}\)C; hot air humidity, 48.003%; initial moisture content, 23.8%; hot air speed, 0.7 m/s; and slow-drying ratio, 3.55. At this time, the net drying time was 157.606 min, the waist bursting increase rate was 3.479%, the whole rice rate was 70.454%, the fatty acid value was 20.932 mg, the resistant starch concentration was 20.932 \(\mu\)g/g, the germination rate was 94.151%, the protein mass fraction was 8.531 g/100 g, and the fat mass fraction was 2.372 g/100 g.  
The optimized parameters were used to conduct the validation tests. To eliminate random errors, three parallel experiments were conducted, and the test results are shown in Table 7. The analysis showed that the average error between the test value and the software optimization parameter value was 3.71%, indicating that the test results were basically consistent with the optimization results and that the selection of influencing factors of rice drying quality was reasonable [38].  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Trial Group** & **Dtn (min)** & **ACP (\%)** & **HRY (\%)** & **FAV (mg)** & **RSC (\(\mu\)g/g)** & **PG (\%)** & **PCV (g/100 g)** & **FCV (g/100 g)** \\ \hline
1 & 165.82 & 3.46 & 68.90 & 21.05 & 193.51 & 97.30 & 7.73 & 2.24 \\ \hline
2 & 159.92 & 3.51 & 69.26 & 20.22 & 196.51 & 93.79 & 8.01 & 2.68 \\ \hline
3 & 158.53 & 3.63 & 69.96 & 19.96 & 200.33 & 95.18 & 8.89 & 2.49 \\ \hline
4 & 161.67 & 3.46 & 72.39 & 21.02 & 189.53 & 93.86 & 8.96 & 2.42 \\ \hline Average test value & 161.49 & 3.52 & 70.13 & 20.56 & 194.97 & 95.03 & 8.40 & 2.46 \\ \hline Model predicted value & 157.60 & 3.48 & 70.45 & 20.93 & 193.64 & 94.15 & 8.53 & 2.37 \\ \hline Model error & 2.47\% & 1.18\% & \(-\)0.46\% & \(-\)1.78\% & 0.69\% & 0.93\% & \(-\)1.54\% & 3.71\% \\ \hline \hline \end{tabular} Note: The contents of protein and fat in unpublished grains were 7.58 and 1.9 g/100 g, respectively. To verify the established regression model, four groups of parameter values were randomly generated within the range for verification experiments. The predicted values were obtained according to the regression equation, and the relative errors between the experimental values and the predicted values were calculated. As shown in Table 8, the relative average errors between the experimental values and the model values were all within 6% [25; 26], indicating that the model can effectively predict various indicators.  
\end{table}
Table 7: Test results of optimized parameters.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Indicators** & **Trial Group** & **T (\({}^{\circ}\)C)** & **RH (\%)** & **MC (\%)** & **V (m/s)** & **TR** & **Predicted Value** & **Actual Value** & **Error** \\ \hline \multirow{4}{*}{Dtn (min)} & 1 & 38.2 & 33.1 & 22.5 & 0.44 & 1.9 & 157.52 & 160.84 & 2.11\% \\ \cline{2-9}  & 2 & 51 & 40.5 & 22.1 & 0.75 & 2.9 & 80.69 & 84.98 & 5.32\% \\ \cline{2-9}  & 3 & 42.4 & 49 & 22.8 & 0.73 & 3.6 & 149.3 & 144.18 & \(-\)3.43\% \\ \cline{2-9}  & 4 & 47.6 & 40.4 & 23.2 & 0.4 & 1.5 & 183.52 & 178.47 & \(-\)2.75\% \\ \hline \hline \end{tabular}
\end{table}
Table 8: Predicted and actual values of each response index.