## 3 Results and Discussion
### Structural Properties of RD-DF
#### 3.1.4 Thermal stability analysis  
The differential TGA curves for RB-DF at various treatment stages were obtained from the first derivatives of weight loss rate (Figure 4). D-RB, RB-DF, EH-DF, and HPH-DF showed a weight loss peak (\(\sim\)3%) at 100 \({}^{\circ}\)C, attributed to the evaporated water. The TGA curves of the four samples had significant differences, whereas that for D-RB showed only one significant weight loss peak at 320-390 \({}^{\circ}\)C, and the corresponding weight loss weight was 42%, where 350 \({}^{\circ}\)C was its thermal decomposition temperature. For RB-DF, two weight loss peaks were observed at 290-360 \({}^{\circ}\)C and 380-500 \({}^{\circ}\)C, with thermal decomposition at 330 \({}^{\circ}\)C. The weight loss region for EH-DF was 278-397 \({}^{\circ}\)C, with thermal decomposition at 320 \({}^{\circ}\)C. Finally, for HPH-DF, the thermal decomposition temperature was 315 \({}^{\circ}\)C, with weight loss area at 260-380 \({}^{\circ}\)C corresponding to a 55% thermal weight loss rate, and a second weight loss area at 410-500 \({}^{\circ}\)C, where thermal loss weight loss rate reached 74%. An increase in weight loss rate is often accompanied by a decrease in thermal decomposition temperature [31; 32]. In agreement with this, the weight loss rate of the four samples changed from 42-74%, and the thermal  
Figure 2: X-ray diffraction patterns of rice bran dietary fiber at different treatment stages. Inset shows main diffraction peaks about rice bran in four treatment stages. _D-RB_ defatted rice bran, _EH-DF_ cellulase enzymatic treatment rice bran dietary fiber, _HPH-DF_ high-pressure treatment rice bran dietary fiber, _RB-DF_ rice bran dietary fiber.  
decomposition temperature decreased from 315-350 \({}^{\circ}\)C. According to the abovementioned data, the thermal decomposition temperature and thermal stability of RB-DF decreased significantly (\(p<\)0.05) following enzymatic hydrolysis and HPH treatment. It is possible that cellulase hydrolysis leads to cellulose particle loosening on the surface, with the subsequent high-pressure homogenization treatment reducing the particle size, and thus increasing the specific surface area. Additionally, a large number of active groups in RB-DF were exposed, increasing the surface adsorption capacity for low molecular weight fragments of cellulose, residual hydrogen ions, etc. These reactive groups, surface defects, and adsorbed residual ions led to RB-DF absorbing heat at a lower thermal decomposition temperature (315 \({}^{\circ}\)C vs. 330 \({}^{\circ}\)C) and to self-decompose.  
Figure 4: Differential thermogravimetric analysis curves of rice bran dietary fiber at different treatment stages. _D-RB_ defatted rice bran, _EH-DF_ cellulase enzymatic treatment rice bran dietary fiber, _HPH-DF_ high-pressure treatment rice bran dietary fiber, _RB-DF_ rice bran dietary fiber.  
Figure 3: Infrared spectra of rice bran dietary fiber at different treatment stages. _D-RB_ defatted rice bran, _EH-DF_ cellulase enzymatic treatment rice bran dietary fiber, _HPH-DF_ high-pressure treatment rice bran dietary fiber, _RB-DF_ rice bran dietary fiber.