## 3 Results and Discussion  
### Effect of Ingredients and Process Variables on the Extrusion-Cooking Process  
Fruit, vegetable and oilseed pomace is a valuable raw material for enriching extruded snack recipes. They can improve the nutritional value of products, introduce interesting flavours and colours and support sustainability by reducing waste. The extrusion process may be the optimal way to use this type of waste from the food industry. The study produced results that confirm the potential of using fruit, vegetable and oilseeds pomace as an ingredient to enrich the formulation of extruded snacks (Figure 1). Most of the snack pellets with the addition of by-products were characterized by a smooth and uniform texture without blisters. In the case of products with 20 and 30% ingredients, it was possible to notice inclusions of selected pomace (in particular, chokeberry and pumpkin pomace), which were strongly visible in the gelatinized structure of the extrudates (Figure 2). This is an extremely desirable feature for manufacturers, since a product with such a structure is more attractive among consumers, who expect products with increased health-promoting potency. The introduction of fruit, vegetable and oilseed pomace not only influenced the finished product but also significantly affected the extrusion-cooking process. The findings of numerous preceding experiments [20; 21; 22; 23; 24] have demonstrated that the screw speed exerts a considerable influence on the efficacy of the extrusion-cooking process. The outcomes of the present study indicated that, by elevating the screw speed during the processing of the majority of raw material mixtures, there was a notable enhancement in the efficiency of the extrusion-cooking. High screw speed promoted increased material flow through the extruder, resulting in higher production. The highest efficiency for most processed mixtures were observed with the highest percentage of pomace. The highest efficiencies were obtained when processing a blend enriched with 30% addition of nigella seed pomace at 80 rpm (26.00 kg/h) and the lowest for a blend with 20% addition of pumpkin pomace processed at 40 rpm (6.76 kg/h) (Figure 3). In addition, extended efficiencies were observed for blends with the addition of oilseed pomace (flaxseed and nigella seed) compared to  
Figure 1: Snack pellets without addition (**a**) and from left with 10, 20 and 30% pomace: (**b**) chokeberry pomace; (**c**) apple pomace; (**d**) pumpkin pomace; (**e**) nigella seed pomace; (**f**) flaxseed pomace. Figure 2: Snack pellets (intermediate product) with 30% pomace: (**a**) pumpkin pomace; (**b**) chokeberry pomace. other blends. This was due to the larger quantity of fat, the presence of which affects the flow of the mixture through the extruder cylinder. Similar correlations were presented by [PERSON] and [PERSON] [25], where they showed that auger speed leads to an increase in the efficiency of the extrusion-cooking process of potato pellets with the addition of fresh vegetables such as onions, leeks, kale and carrots. Conversely, [PERSON] et al. [24] demonstrated in a study on the impact of fresh broccoli on extrusion-cooking efficiency that an increase in the proportion of broccoli resulted in a corresponding enhancement efficiency, particularly at additions of 20% and 30%. During the extrusion-cooking process of snack pellets enriched with plant pomace, irregularities in electricity consumption were observed depending on the proportion of pomace addition. Depending on the type of ingredient for most of the processed mixtures, the highest value of SME was at a similar level, amounting to pumpkin pomace mixture 0.118 kWh/kg, apple pomace mixture 0.108 kWh/kg, nigella seed pomace 0.100 kWh/kg, and flaxseed 0.083 kWh/kg. For the mixture enriched with chokeberry pomace, a reduction in the index was observed, with the highest value being 0.034 kWh/kg. The lowest SME values were similar for all ingredients, ranging from 0.008 to 0.013 kWh/kg (Figure 4). A study presented by [PERSON] et al.