## 4 Discussion  
The experimental results show that the drying efficiency and WL of bread slices varied statistically significantly across the four methods (A, B, C, and D). Method C achieved the lowest WL (25.0 \(\pm\) 0.1 g) while method D achieved the highest WL (29.8 \(\pm\) 0.1 g, Table 1). This aligns with findings in the literature where higher IR power and shorter distances enhance drying rates due to increased energy transfer and surface temperature [33; 34], but we must also include the differences in the initial masses of bread slices for drying. The measured and integrated weight loss followed similar trends, with method B showing the smallest differences (WL\({}_{\rm m}\) = 28.0 \(\pm\) 0.1 g, WL\({}_{\rm t}\) = 27.8 \(\pm\) 0.1 g). This suggests greater consistency and uniformity in drying performance under higher IR power at a closer distance. These results are consistent with studies on hybrid infrared-convective drying systems, where synergistic effects of IR radiation and convective air enhance moisture diffusion  
Figure 8: PCA of independent variables and responses during the CIRD drying of bread slices. Figure 7: A color correlation diagram illustrating the relationship between the independent variable parameters and the responses in CIRD. and evaporation rates [35; 36]. The experimental results are supported by prior research showing that increased radiation intensity or reduced emitter-sample distance accelerates drying by raising surface temperatures and enhancing moisture migration [2; 37; 38]. Similar to results for apple slices, dried under combined IR-hot air conditions, higher IR intensity significantly reduced drying time and improved efficiency (Table 2). The rapid diffusion of moisture under high-intensity IR radiation is a shared characteristic. The synergistic effect of combining IR with convection has been shown to reduce energy consumption while maintaining product quality. This is particularly evident in method B's superior performance at lower total weights. The results of this study reveal significant differences in drying time and energy consumption across the four experimental methods (A, B, C, and D). Method B achieved the shortest drying time 90 min) and relatively low total energy consumption (E = 0.655 \(\pm\) 0.026 kWh), demonstrating the most efficient drying performance. This aligns with findings in previous studies on combined infrared-convective drying systems, where higher IR power and shorter emitter-sample distances accelerate moisture removal due to rapid surface heating and enhanced mass transfer [30; 39]. Conversely, method D required the longest drying time (220 \(\pm\) 7 min) and consumed the highest total energy (0.976 \(\pm\) 0.018 kWh). The increased distance and lower IR power likely reduced the intensity of radiation reaching the bread surface, resulting in slower moisture diffusion. Similar observations have been reported in previous research, where lower IR intensity or greater emitter-sample distances led to prolonged drying times [30; 40]. Energy efficiency varied significantly among the methods, with method B showing the highest efficiency (23.393 \(\pm\) 0.171 kWh/kg) and method C showing the lowest (32.734 \(\pm\) 1.627 kWh/kg). The high energy efficiency of method B can be attributed to its optimal combination of high IR power and short distance, which maximized energy utilization for moisture removal. Previous studies on hybrid infrared-convective systems have similarly demonstrated that combining high-intensity IR radiation with convective air enhances energy efficiency by reducing heat losses [33; 35]. In contrast, method C's low indicates inefficiencies associated with increased emitter_sample distance despite using a high-power IR lamp (250 W). This finding is consistent with the literature emphasizing that closer emitter placement improves energy efficiency by concentrating thermal energy on the material surface [35; 41].