Effect of drying and extrusion processing on physical and nutritional characteristics of bilberry press cake extrudates
Journal article, 2018
Mild drying and extrusion processing of side streams from berry juice production can enable retention of valuable
compounds in the food chain and reduce waste production. The aim of this study was to evaluate the
applicability of using hot air (HA) and microwave assisted hot air (MWHA) drying combined with extrusion for
conversion of bilberry press cake into value-added extruded food products. Bilberry press cake was dried at 40 °C
by HA and MWHA drying to a moisture content of 17 g/100 g. A twin screw extruder (average feed rate 72 g/
min, temperature profile 135-128-89-69 °C) was used to extrude products containing organic wholegrain rye
flour and 10% or 25% dried bilberry press cake powder. A consumer panel (n=15) evaluated four extrudates on
hedonic and Just-About-Right (JAR) scales, with a main focus on texture properties. The results indicate that
different drying techniques implied a difference in processing time (40% reduction with MWHA drying).
However, the retention of total phenolics and physical characteristics of extruded snacks containing bilberry
powders were independent of drying techniques. In sum, powder of bilberry press cake can be incorporated in
cereal based extruded snacks with enhanced phenolic content and potential for palatable sensory properties.