## 3 Results
### ER, BD, WAI and WSI
\begin{table}
\begin{tabular}{l c c c c} \hline \hline  & **CES 0** & **CES 2** & **CES 4** & **CES 6** \\ \hline ER & 4.72 \(\pm\) 0.08 \({}^{\text{a}}\) & 4.39 \(\pm\) 0.12 \({}^{\text{b}}\) & 4.63 \(\pm\) 0.08 \({}^{\text{a}}\) & 4.71 \(\pm\) 0.16 \({}^{\text{a}}\) \\ BD (kg/m\({}^{3}\)) & 32.44 \(\pm\) 1.33 \({}^{\text{c}}\) & 33.86 \(\pm\) 1.41 \({}^{\text{c}}\) & 41.37 \(\pm\) 2.32 \({}^{\text{b}}\) & 44.26 \(\pm\) 1.81 \({}^{\text{a}}\) \\ WAI & 5.05 \(\pm\) 0.22 \({}^{\text{a}}\) & 4.30 \(\pm\) 0.16 \({}^{\text{b}}\) & 4.37 \(\pm\) 0.18 \({}^{\text{b}}\) & 4.06 \(\pm\) 0.12 \({}^{\text{b}}\) \\ WSI (\%) & 36.85 \(\pm\) 1.12 \({}^{\text{c}}\) & 43.06 \(\pm\) 1.43 \({}^{\text{b}}\) & 45.51 \(\pm\) 1.66 \({}^{\text{ab}}\) & 46.73 \(\pm\) 1.28 \({}^{\text{a}}\) \\ \hline \hline \end{tabular} Different letters in the same row indicate significant differences between corn-based extruded snacks formulations (\(p<0.05\)); CES 0—control corn-based extruded snacks; CES 2—corn-based extruded snacks with 2% BPP addition; CES 4—corn-based extruded snacks with 4% BPP addition; CES 6—corn-based extruded snacks with 6% BPP addition.  
\end{table} 
Table 3: Effect of BPP addition on ER, BD, WAI, and WSI of corn-based extruded snacks. [PERSON] et al. [14] found a mean expansion ratio of 4.24 for control cornmeal-based extrudates and values between 3.89 and 4.58 for corn extrudates with a 5-20% addition of fruit pomace. In their study, the addition of 5% chokeberry pomace resulted in the rise of the expansion ratio from 4.24 to 4.58. Other studies also reported an increase in the expansion ratio in corn-based extruded snacks supplemented with chokeberry pomace powder [3] or with apple, white mulberry, and blackberry powders [17] at a 5% addition level compared with the control products. However, [PERSON] et al. [4] reported a decrease in the expansion ratio as the barberry powder addition level increased in puffed corns (2.5% to 10%) and attributed this effect to the low starch but high fiber content of barberry powder. Other studies also reported increasingly large decreases in the expansion ratio of corn-based extruded snacks as the level of addition of fruit powders [17] or blackcurrant and chokeberry press residue [3] increases to 10, 15, or 20%. The bulk density is influenced by the composition of the raw blend and by the expansion process. For the same raw blend, there is an inversely proportional relationship between the expansion ratio and bulk density [11]. The bulk density of the 2% BPP-supplemented corn-based extruded snacks (CES 2, 33.86 kg/m\({}^{3}\)) was closer to the control (CES 0, 32.44 kg/m\({}^{3}\)). Similar values have been reported previously by [PERSON] et al. [17] in corn-based crigs (33.58-42.50 kg/m\({}^{3}\)) and in those supplemented with 5% apple powder (44.11-55.72 kg/m\({}^{3}\)). The addition of 4% and 6% BPP resulted in a significantly (\(p<0.05\)) higher bulk density of the corn extrudates compared with the control, even if the expansion ratio recorded the same values. This was related to the components that BPP provides, including protein and dietary fiber. [PERSON] et al. [14] also found an increasing trend of the extrudates bulk density as the cherry, chokeberry, or blackcurrant pomace addition level increased. Table 3 presents the results of WAI and WSI of control and BPP-supplemented corn-based extruded snacks. The water absorption index (WAI) and water solubility index (WSI) describe the functional properties of extruded products. WAI expresses the amount of moisture absorbed by starch during extrusion, and it is a measure of starch gelatinization, while WSI indicates the extent of starch degradation by quantifying the soluble components resulting from extrusion. The WAI decreased while WSI increased with the increasing addition levels of BPP in corn-extruded snacks. Water absorption of supplemented BPP corn-extruded snacks was significantly (\(p<0.05\)) lower than control, but differences between formulations with various BPP addition levels were not statistically significant (\(p>0.05\)).