Plant-based products with good nutritional and sensory quality are needed to facilitate dietary change towards using less of the unsustainable animal origin foods. Extrusion cooking is a way to produce these products cost effectively. A high quality dry-extruded product has porous structure and suitable hardness. These properties can be affected by adjusting the viscosity of the extruded mass. This master’s thesis discusses the properties of colloidal microcrystalline cellulose (cMCC) that affect the structure of dry-extruded textured protein products made of potato protein and faba bean flour made from germinated beans. The aim was to produce a porous, water binding domestic plant-protein product that can be used as part of healthy diet. The hypothesis was that cMCC increases water absorption capacity and changes the stiffness and expansion of the product by increasing viscosity of the mass. The viscosity of raw materials was first examined from flour mixtures and after this mixture of 70:30 faba bean:potato protein with 0; 1.5 and 3.0 % cMCC was extruded in 24; 27 and 30 % water contents. Moisture content, water absorption capacity, water solubility, sectional expansion index, physical properties of dry and swollen extrudates were examined. Products were photographed both dry and after swelling. The nutritional compositions were calculated based on raw material manufacturers’ information. The swollen products contained 15–22 g protein, 11–17 g carbohydrates and 3,5–47,7 fiber g/100 g moist extrudate (31–42 % dry matter) and could be categorized as source of fiber. cMCC improved flowing capabilities of the flour mixture which was observed as more uniform shape of extrudates. Cleaning the equipment was significantly easier with mixtures containing cMCC. cMCC did not increase water absorption capacity but it did decrease water solubility and increased stiffness. Viscosity measurements revealed that potato proteins did not gel. This information could not be utilized in detail to predict viscosities with extrusion because of different flour ratios.