## 3 Results and Discussion
### Impact of Ingredients and Processing Conditions on Extrusion-Cooking Process
This low energy consumption may be attributed to the presence of natural fruit juices, which likely increase the plasticity of the mixture and facilitate material flow through the extruder-cooker, thereby reducing flow resistance during processing. This effect is likely due to the shorter residence time of the material in the plasticizing section at higher speed, which leads to less intense mechanical processing. At the highest blueberry addition level (30%), SME values began to increase again, particularly at higher screw speed. For example, at 100 rpm and 32% moisture, SME reached 0.021 kWh/kg, a value comparable to control sample. This suggests that an excess of fruit may lead to inconsistencies in the structure of the processed mass, resulting in higher friction within the extruder-cooker and thus increased mechanical energy demand. Moisture content of the mixture also influenced SME values, although the effect was less consistent. For the control sample, increasing moisture from 32% to 36% at 60 rpm led to a decrease in SME, which can be explained by improved slippage and reduced internal friction. However, in mixtures with 30% blueberry, the trend was reversed--SME increased with higher moisture levels. This may indicate that the optimal hydration level was exceeded, leading to deterioration in the rheological properties of the raw material and greater mechanical resistance during processing. The lowest specific mechanical energy consumption (SME) was recorded for the mixture with 10% blueberry, at 36% moisture and a screw speed of 100 rpm, reaching 0.003 kWh/kg. In contrast, the highest SME was observed for the mixture without blueberry, at 32% moisture and 60 rpm, with a value of 0.038 kWh/kg. This indicates a more than threefold difference between the extreme cases, highlighting the strong influence of both formulation and process parameters on energy efficiency during extrusion-cooking process. The authors also found that increasing the moisture content of the mix, especially when combined with fresh blueberries, resulted in a decrease in SME. The water from the fruit further improved hydration, reduced flow resistance and lowered the mechanical energy needed for processing. A similar effect was observed in the study by [PERSON] et al. [36] where the impact of extrusion-cooking process parameters on the physical properties of rice and mushroom-based snacks was analyzed. The authors showed that at the highest raw material moisture content (18%), the SME value decreased. Feed moisture content in this research was from 12 to 18%. SME results were in the range of 198.69-416.11 kJ/ kg. This was explained by better slippage of the mixture inside the extruder and lower mechanical resistance. [PERSON] et al. [37] also observed a decrease in SME with increasing moisture content and temperature during the extrusion of lentil protein isolate in the form of textured vegetable protein. The specific mechanical energy (SME) values ranged from 126.0 to 66.9 Wh/kg. The authors explained this effect by the reduced viscosity of the mixture and better slippage of the material inside the extruder-cooker barrel. As a result, mechanical resistance decreased, leading to lower energy requirements during processing. Feed moisture content in this research was from 30 to 40%.