Thermo-mechanical processing of fibre-rich blackcurrant pomace to modify techno-functional properties

Abstract

Abstract Exploring the use of seedless blackcurrant pomace, a fibre-rich by-product of juice pressing, in foods is favourable due to its nutritional profile but also for economic and sustainability aspects. Current applications are limited to products in which rapid fibre swelling, high water solubility or low sedimentation is not essential. In this study, functional properties of seedless blackcurrant pomace were modified by thermo-mechanical treatments using extrusion cooking or micronization in a planetary ball mill. A full factorial design showed that low pomace moisture (11 g/100 g) had the highest impact on swelling capacity (+ 20.6%) and water solubility index (+ 23.2%), whereas variation in extrusion temperature exhibited only minor effects. After milling for 4 h, the median particle size was reduced by 98% to 4 µm and the specific surface area increased from 0.1 to 2.5 m 2 /mL. Swelling capacity was highest after this time with 7.6 mL/g pomace and, although the amount of extractable sugars was reduced, water solubility increased to 7.6 g/100 g. In contrast to extruded samples, the red colour of the pomace was intensified after milling. Both treatments appear as promising to extend the applicability of fruit by-products in foods, as micronized pomace may counteract sedimentation in liquids, whereas increased swelling capacity after extrusion may have stabilizing effects on yoghurt-like systems.