## 3 Results and Discussion
### Impact of Ingredients and Processing Conditions on Extrusion-Cooking Process
The authors demonstrated that both screw speed and raw material composition significantly affected process performance--highest efficiency was achieved at higher screw speeds and moderate moisture content. The results have shown that an increase in the screw speed from 60 to 100 rpm led to a significant increase in process efficiency (from 10.56 to 16.8 kg/h). At the same time, [PERSON] et al. observed that plant-based additives rich in fiber may lead to higher flow resistance, thereby reducing process efficiency. This observation is consistent with the current findings, where increasing the fresh blueberry content to 30% resulted in a notable decline in efficiency, particularly at higher moisture content. In summary, the highest throughput (37.12 kg/h) was achieved with a mixture containing 10% blueberry, 32% moisture, and a screw speed of 100 rpm. This suggests the presence of an optimal fruit addition level, which under favorable conditions may enhance rather than hinder process efficiency. Conversely, the lowest efficiency (14.40 kg/h) was \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Blueberry Addition** **[\%]** & **Screw Rotation** **[rpm]** & **Moisture** **[\%]** & **Q** **[kg/h]** & **SME** **[kWh/kg]** \\ \hline \multirow{4}{*}{0} & \multirow{4}{*}{60} & 32 & 20.08 \(\pm\) 0.37 b  & 0.038 \(\pm\) 0.001 c  \\  & & 36 & 21.84 \(\pm\) 0.24 c  & 0.034 \(\pm\) 0.000 b  \\ \cline{2-5}  & \multirow{4}{*}{100} & 32 & 34.08 \(\pm\) 1.25 f  & 0.016 \(\pm\) 0.001 abc  \\  & & 36 & 36.16 \(\pm\) 0.28 g  & 0.022 \(\pm\) 0.000 abc  \\ \hline \multirow{4}{*}{10} & \multirow{4}{*}{60} & 32 & 22.96 \(\pm\) 0.50 d  & 0.009 \(\pm\) 0.003 ab  \\  & & 36 & 21.68 \(\pm\) 0.60 c  & 0.012 \(\pm\) 0.001 abc  \\ \cline{2-5}  & \multirow{4}{*}{100} & 32 & 37.12 \(\pm\) 0.14 h  & 0.005 \(\pm\) 0.001 a  \\  & & 36 & 34.64 \(\pm\) 0.97 f  & 0.003 \(\pm\) 0.000 a  \\ \hline \multirow{4}{*}{30} & \multirow{4}{*}{60} & 32 & 19.12 \(\pm\) 1.08 b  & 0.015 \(\pm\) 0.013 abc  \\  & & 36 & 14.40 \(\pm\) 0.00 a  & 0.021 \(\pm\) 0.022 abc  \\ \cline{2-5}  & \multirow{4}{*}{100} & 32 & 28.88 \(\pm\) 0.14 d  & 0.021 \(\pm\) 0.018 abc  \\  & & 36 & 23.28 \(\pm\) 0.00 e  & 0.017 \(\pm\) 0.008 abc  \\ \hline \end{tabular}
\end{table} 
Table 4: Results of extrusion-cooking efficiency and energy consumption of snack pellets. recorded for the mixture with the highest moisture (36%) and blueberry content (30%), processed at the lowest screw speed (60 rpm). The results of the analysis showed that SME (Specific Mechanical Energy) was notably affected by the process parameters, including screw speed, blueberry content, and the moisture level in the mixture (Table 4). A significantly decreasing trend in SME was observed with increasing screw speed and higher content of fresh blueberry addition in the raw material composition. The highest SME values were observed for samples without blueberry addition, processed at the lower screw speed of 60 rpm--measuring 0.038 kWh/kg (at 32% moisture) and 0.034 kWh/kg (at 36%). However, when the screw speed increased to 100 rpm, the mechanical energy consumption decreased noticeably. For the same samples (without blueberry), SME dropped to 0.016 kWh/kg (32%) and 0.022 kWh/kg (36%). The decrease in SME with the increase in rotational speed for the control sample may result from the decrease in the viscosity of the processed mass due to the higher thermomechanical interactions at higher rotational speeds [35]. The whole process affects the easier liquefaction of the suspension and the easier flow of the material through the plasticizing system, which ultimately affects the lower energy consumption of the device. The addition of fresh blueberries had a significant effect on reducing SME, especially at the 10% addition level. The specific mechanical energy values in this group were among the lowest recorded across all tested samples. The minimum SME was noted at 0.003 kWh/kg (100 rpm, 36% moisture).