## 3 Results and Discussion
### Bulk Density and Flowability of Insect Powders  
Table 3 presents the loose and tapped bulk densities and the Hausner ratio of black soldier fly larvae powders. The IR-CD method resulted in significantly higher loose and tapped bulk densities than the CD method. Similar findings were reported by [PERSON] et al. [55] and [PERSON] et al. [56], who also observed differences in the bulk densities of edible insect powders obtained by different drying methods. For example, using a hot air oven and microwave drying, [PERSON] et al. [30] obtained bulk densities of 381.54 and 494.58 g/dm\({}^{3}\) of black soldier fly larvae powders. In this case, the increased bulk density in IR-CD powders results from the lower particle size (Table 3). Smaller particles can fill the voids between larger particles, resulting in a denser packing structure. The IR-CD may have contributed to obtaining reduced particle sizes compared to CD due to the combined effects of radiation and convective heat transfer. Intense heating from IR can cause rapid water evaporation [57], leading to micro-crack formation and weakening of the dried material structure. This increased breakability facilitates the breakdown of particles during subsequent grinding, resulting in finer powders. Additionally, surface fats may influence interparticle interactions, affecting bulk density. The adhesion between particles can lead to a more connected and stiffer network, affecting the powder's bulk density--higher adhesion results in a denser and more rigid structure [58]. The presence of surface fat can act as a lubricant, reducing friction between particles and thus improving flowability [59]. On the other hand, excess interparticle force between particulate solids can lead to particle agglomeration due to increased cohesion, which can negatively affect flow properties [60]. However, in this study, interparticle forces were small, with a relatively coarse particle size distribution.  
Figure 1: The water vapor adsorption kinetics of black soldier fly powders processed by convective (CD) and infrared convective (IR-CD) drying methods. Dotted lines represent values obtained from mathematical modeling.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Treatment**} & **Particle Size** & **Loose Bulk Density** & **Tapped Bulk Density** & **Hausner Ratio** \\  & **(\(\upmu\)m)** & **(kg/m\({}^{3}\))** & **(kg/m\({}^{3}\))** & **(-)** \\ \hline CD & 631.91 b \({}^{1}\)\(\pm\) 45.34 & 339.11 a \(\pm\) 2.04 & 391.28 a \(\pm\) 2.35 & 1.15 a \(\pm\) 0.01 \\ IR-CD & 241.86 a \(\pm\) 26.10 & 352.73 b \(\pm\) 2.02 & 421.67 b \(\pm\) 4.41 & 1.20 a \(\pm\) 0.09 \\ \hline \hline \end{tabular}
\end{table}
Table 3: The bulk density and flowability of black soldier fly powders processed by convective (CD) and infrared convective (IR–CD) drying methods.  
Bulk density is an important factor influencing the flowability of powders. Higher bulk density can reduce void spaces between particles, potentially enhancing flowability by minimizing interparticle friction. However, this relationship is complex, as increased bulk density might also result in greater particle cohesion, adversely affecting flow properties. More significant differences between tapped and loose bulk densities indicate a higher Hausner ratio, which indicates less fluid powders. Based on the Hausner ratio (Table 3), CD powder exhibited good (for HR values between 1.12-1.18), and IR-CD revealed fair (for HR values between 1.19-1.24) flow characteristics [61].