## 3 Results and Discussion  
### Solubility of the Proteins  
Protein solubility is a crucial factor that influences various functional properties, making it a critical determinant of protein functionality in the food-processing industry. The impact of pH and ionic strength on the protein isolates derived from BSF larvae was investigated, and the findings are illustrated in Figure 2. The solubility of the BSF larvae proteins followed a characteristic U-shaped curve within the examined pH range [2; 3; 4; 5; 6; 7; 8; 9; 10], indicating a substantial dependence on pH. The solubility of the AAFSO and AAFSISO proteins was significantly (\(p<0.05\)) greater than that of the AAF and AAFSI proteins at pH 4-8 (Figure 2). The greatest levels of solubility were recorded at pH 2 (89% for AAFSISO) and pH 10 (85.21% for AAFSSO), which were likely due to the attainment of the pI of protein bonds. These solubility patterns were consistent with those reported in previous studies [15; 21; 25]. Additionally, the results revealed that the BSF larvae isolates demonstrated remarkably enhanced solubility results at pH 2 compared to pH 8 and 10, with the exception of the AAFSO protein group. This finding aligns with prior research that reported enhanced _Tenebrio molitor_ protein solubility at pH 2 compared to pH 10 [30]. According to our research findings, protein solubility at weakly acidic, alkaline, and neutral pH levels is a crucial aspect for industrial applications. Our BSF larvae meet these criteria and can be utilized in acidic food environments, including nutrition and sports drinks, as well as acidified sauces. The solubility of insect proteins may vary depending on their individual characteristics, and some proteins may aggregate and precipitate, while others may remain soluble. Our results show that both AAF and AAFSI had the lowest solubility at pH 4, while AAFSISO had the highest solubility at pH 2, which may be related to surface hydrophobicity, which is an important factor affecting solubility (Table 1). The addition of salt and the presence of ligands can influence protein solubility, serving are extrinsic factors that impact protein solubility [31]. The findings of the study suggest that the high concentration of (NH4)2 SO4 can preserve the structure of proteins, leading to improved solubility [32]. No notable difference (\(p>0.05\)) in the solubility was noted when NaCl was added to the solution at pH 2. This could be attributed to the proteins being surrounded by salt counter-ions, which neutralize surface charges and either decrease or increase electrostatic interactions between protein molecules [33]. The literature does not contain information on the protein solubility profile of BSF larvae protein extracts via salt treatment. These results indicate that both salting-in and salting-out methods can be employed to extract insect proteins. The efficacy of these methods is contingent upon the extent to which they have been optimized for the specific extraction process, as well as the degree to which the method of extraction conforms to the unique \begin{table}
\begin{tabular}{c c c} \hline \hline
**Extraction Method** & **Surface Hydrophobicity** & **Bulk Density (g/L)** \\ \hline AAF & 1056.41 \(\pm\) 0.93  \\ AAFSI & 1021.37 \(\pm\) 4.08  \\ AAFSSO & 594.59 \(\pm\) 8.47  & 1.15 \(\pm\) 0.06  \\ AAFSISO & 540.02 \(\pm\) 6.45  & 1.52 \(\pm\) 0.03  \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Effect of extraction methods on surface hydrophobicity and bulk density of black soldier fly larvae protein isolates. Figure 2: Impact of extraction methods on solubility of black soldier fly larvae isolates obtained by AAF (alkaline–acid extraction—black pentagon), AAFSI (salting-in technique—red circle), AAFSO (salting-out technique—blue triangle), and AAFSISO (salting-in and out technique—green stars). Error bars show standard deviation. attributes of the protein under investigation, thereby ensuring the efficient and effective isolation of the protein while simultaneously preserving its integrity and functionality.