Impacts of the inclusion of various fruit pomace types on the expansion of corn starch extrudates

Abstract

Effects of pomace chemical composition and physical properties (hydration, density, particle size distribution, crystallinity), inclusion level (0, 50, 150, and 300 g/kg), and extrusion processing parameters including, moisture content (150 and 200 g/kg), and screw speed (150, 200, and 250 rpm) of selected fruit (cranberry, blueberry, grape, and apple) pomace-corn starch mixtures, on the expansion of extrudates were studied. All factors had significant main and interaction effects on expansion. Expansion values of pomace were observed in the following order from high to low: apple > cranberry > blueberry > grape at 200 g/kg moisture content. Total dietary fiber and insoluble dietary fiber content of pomace were negatively correlated (p < 0.01) with the expansion. However, a positive correlation between soluble fiber content and expansion ratio was found at 300 g/kg pomace level (p < 0.05). At 300 g/kg pomace level, sugar might have aided to increase the expansion ratio significantly (p < 0.01), suggesting interactions between the fiber, and other components present in the pomace with the starch during expansion. Higher crystallinity might result in a lower expansion (p < 0.01). These results show the presence of positive active interactions between the pomace components and the starch molecules.