Enrichment of starch-based extruded cereals with chokeberry (Aronia melanocarpa) pomace: Influence of processing conditions on techno-functional and sensory related properties, dietary fibre and polyphenol content as well as in vitro digestibility

Abstract

Aiming at providing prototypes for ready-to-eat texturised (RTE) cereal products with reduced glycaemic load, starch blends with chokeberry (Aronia melanocarpa) pomace powder (CPP) rich in dietary fibre (DF) and polyphenols (PP) were extruded using a co-rotating twin-screw extruder. The CPP ratios (25%, 50%) and processing conditions applied (barrel temperature 100 °C, screw speed 200, 400, 600, 800 min−1, water content 13%, 23%) result in specific mechanical energies of 87–336 Whkg−1 and material temperatures of 111–155 °C. Extrudates containing 25% CPP still offer acceptable techno-functional and sensory related physical properties, while higher CPP ratios result in decreased expansion and cell pore size of the slightly darker and softer extrudates. The in vitro glucose release of both extruded blends is reduced by 25% and 50%, respectively. The DF contents are unaffected. As expected, anthocyanins are degraded by about 70% in both blends while phenolic acids and flavonols are fully retained. All PP are already accessible during the stomach phase of an in vitro digestion and are not changed significantly in the intestinal phases. Overall, these data substantiate, that marketable texturised RTE extruded cereals may be developed based on the results presented and on further sensory analysis.