Effect of Moisture Content on Extrusion Modes and Physicochemical Properties of Extrudates with the Addition of Chokeberry Pomace Enzymatic Hydrolysate

The study aimed to investigate the effect of moisture content during the extrusion of a mixture of rice groats and enzymatic hydrolysate of chokeberry press cake on the process parameters as well as the physicochemical, structural-mechanical, and technological characteristics of the resulting product samples. The relevance of the research stems from the need to make technological processes for processing fruit and berry raw materials more environmentally friendly and to improve the efficiency of utilizing secondary raw material resources. Enzymatic hydrolysates of chokeberry press cake were obtained using a complex of enzymes, including pectinase, cellulase, protease, and lipase. The hydrolysate was dried, added to the rice groats at a concentration of 5%, and extruded while varying the moisture content within the range of 15 to 24%. Increasing the moisture content during extrusion decreased the temperature from 165 to 148°C, the pressure in the predie zone from 5.0 to 2.0 MPa, and the shear deformation torque from 88 to 48%, thereby decreasing the intensity of the impact on the biopolymers in the processed mixtures. The specific mechanical energy consumption decreased from 0.17 to 0.09 kW h/kg. The trends in changes to the thermomechanical processing conditions, determined by the amount of water in the system as a factor reducing friction, were identical for both the control and experimental mixtures. As the moisture content increased during extrusion, the hardness of the samples containing the enzymatic hydrolysate of berry press cake increased from 11.1 to 43.5 N and bulk density rose from 97.0 to 278.8 g/dm³. The quadratic expansion coefficient decreased from 8.5 to 3.0. The dynamic viscosity of extrudate suspensions, ground and hydrated to simulate brewing with hot water, significantly increased from 2.0 to 3.4–4.4 Pa·s as the moisture content of the processed mixtures increased. Extrusion also significantly increased the phenolic content in samples with the enzymatic hydrolysate of chokeberry press cake, with the highest observed value of 631.5 mg/dm² corresponding to a moisture content of 15%.