Impact of Hydrocolloids and Homogenization Treatment on the Foaming Properties of Raspberry Fruit Puree

The production of healthy, ready-to-eat fruit snacks by means of foam-mat drying has to face the challenge of ensuring high foam stability throughout the entire process. Foaming properties of raspberry puree whipped for 10min with varying concentrations of potato protein isolate (2.5, 5, 10% w/w) as foaming agent were studied. Furthermore, the impact of hydrocolloids as foam stabilizers, i.e., maltodextrin (5, 15, 30% w/w) and pectin (0.1, 0.25, 0.5, 0.75, 1.0, 2.5% w/w), in combination with the variation of protein concentration as well as the impact of a homogenization treatment of fruit puree on the foam characteristics and puree properties were investigated. Foam stability was enhanced by the increase of protein and hydrocolloid concentration. Maltodextrin and pectin showed similar behavior even though pectin was used at considerably smaller concentrations. Compared to single hydrocolloid systems, the addition of pectin and maltodextrin in combination led to a further enhancement of foam stability, which offered the opportunity to simultaneously decrease the concentration of both hydrocolloids. The destruction of fruit tissue by homogenization treatment resulted in a reduction of mean particle diameters (D[4,3], D[3,2]) and a decrease of viscosity. Despite the increase in the specific surface area (A(SF)) and thus, expected enhanced oxidative processes, no changes were observed for ascorbic acid and anthocyanin contents. However, the structural changes induced by the homogenization treatment significantly affected foaming properties.