# Study of the Targeted Regulation of Rice Drying Characteristics and Quality
## 3 Results and Discussion
### Evaluation of Regression Model and Analysis of Variance
#### 3.2.3 Nutritional Quality  
1. Influence of test factors on fatty acid value (FAV) The fatty acid value reflects an important indicator of rice nutritional value and eating quality. The order of factors affecting FAV was TR > V > RH > T > MC, as shown in Figure 2e of the Factor Contribution Rate. The maximum influence of SRB on fatty acid value was found. The regression model of fatty acid values is shown in Table 4. R\({}^{2}\) of the model was 0.8909, and the CV value was 3.25%. The model had good fitting ability and reliability. As shown in Figure 7, the fatty acid value was positively correlated with air speed and initial moisture and negatively correlated with SRB. This is because when the air speed decreases, the drying rate of rice slows down, and the time of oil exposure to air is prolonged, increasing the possibility of oil oxidation and decreasing the fatty acid value. At the same time, a sustained high air speed destroys the specific spatial structure of enzyme proteins, and the activity of rice lipase decreases, which reduces the production of lipid hydrolysis and free fatty acids in rice, resulting in an increase in the fatty acid value [26]. When the initial moisture is high, it takes longer for rice to remove water during the drying process, which may lead to an increase in the degree of oxidation of fatty acids. A high SRB leads to a slow drying rate, which is conducive to reducing the fatty acid value. 2. Influence of test factors on resistant starch concentration (RSC) Resistant starch, also known as \"indigestible starch\", is recognized as a beneficial dietary fiber. The increase of its concentration can delay the increase of blood sugar, improve the glucose and lipid metabolism and insulin resistance of the body, have a preventive effect on chronic metabolic diseases, play its digestive characteristics, and promote the comprehensive quality of rice [30; 31]. The factor contribution is shown in Figure 2f. The order of factors affecting the resistant starch concentration was V > RH > T > TR > MC. The resistant starch concentration regression model is shown in Table 4. R\({}^{2}\) of the model was 0.9081, and the CV value was 4.34%. The model had good fitting ability and reliability. As shown in Figure 8a, the resistant starch concentration of the RSM reached a peak value. This is because resistant starch can promote the transformation of starch into resistant starch at appropriate temperatures and humidity. However, when the temperature or humidity is too high or too low, it leads to the degradation of starch or the competition of other reaction pathways, thereby reducing the formation of resistant starch. As shown in Figure 8b, the concentration of resistant starch decreased with the decrease in temperature and the increase in initial moisture content and decreased with the decrease in humidity. 3. Influence of test factors on the protein change value (PCV) Protein content can affect the nutritional value and processing quality of rice. The difference in the protein content before and after drying under different technological conditions is calledthe protein change value. The contribution rate of each factor is shown in Figure 2g, and the regression equation of the protein change value is shown in Table 4. The order of factors affecting HRY was V > MC > RH > TR > T. R2 of the model was 0.89, and the CV value was 4.46%. The model had good fitting ability and reliability. As shown in Figure 9, the interaction between the initial moisture content and air speed was obvious. The protein change value at low initial moisture content was sharper than that at high initial moisture content and increased with an increase in air speed. The protein change value was highest at low sensitivity and high air speed [32; 33; 34]. A high air speed for too long promotes the change in rice grain germ organization structure, accelerates the oxidation degeneration of protein, and thus reduces the protein content [35; 36; 37].