Influence of grain–blackcurrant distillers’ stillage on the properties of extruded corn–rice crispbreads

The study investigated the effect of grain–blackcurrant distillers’ stillage as a secondary raw material of the distillation process on the extrusion parameters, structural–mechanical properties, and nutritional characteristics of corn–rice crispbreads. The stillage was obtained after distillation of mash produced by fermenting a mixture of wheat and blackcurrant pomace remaining after juice pressing. Extrusion of mixtures containing 5–15% stillage proceeded steadily; with an increase in its proportion, the process pressure decreased from 2.3 to 1.9 MPa without changes in temperature and torque. A reduction in the vertical expansion ratio of the strand from 9.7 to 7.3 was observed, which is typical for starch-containing systems when non-starch components are incorporated. At the same time, extrudate hardness remained unchanged, whereas the number of microfractures increased from 10.9 to 13.2, indicating the formation of a more uniform, fine-pored structure with improved crispness. Nutritional evaluation of the crispbreads demonstrated that the addition of 15% stillage increased protein content by 69%, dietary fiber by 110%, and phenolic compounds by 62% compared with the control. Comparison of calculated and experimental values revealed a consistent excess of actual phenolic content over theoretical estimates by up to 50% at the maximum dosage. This effect is attributed to the enzymatic treatment of blackcurrant pomace, as well as the thermomechanical action of extrusion, which facilitate the breakdown of cell walls and release of bound polyphenols. The results confirm the potential of grain–blackcurrant distillers’ stillage as an ingredient for the production of extruded crispbreads enriched with protein, dietary fiber, and phenolic compounds. Incorporation of this resource allows for targeted improvement of the nutritional and sensory profile of products without compromising technological stability of the process.)