Passion fruit shell flour and rice blends processed into fiber-rich expanded extrudates

Abstract

Novel formulations of passion fruit shell flour and rice blends were processed on a single-screw extruder, into value-added extrudates. The effects of extrusion processing variables of die temperature, feed moisture, and passion fruit shell flour content on the sectional expansion (SEI), longitudinal expansion (LEI), water absorption (WAI), and water solubility (WSI) indices of the extrudates were evaluated using a central composite design. The processing variables caused a marked effect on all the independent variables studied (SEI, LEI, WAI, and WSI). Passion fruit shell flour used in this study contained 56.76% of crude fiber. Additionally, the microstructural view of the cross-sectional areas, internal structure and surface appearance of extrudates containing 0–15% passion fruit shell flour in their formulation revealed that the addition of passion fruit shell flour led to a decrease in expansion and cell size, increase in thickness of air cell wall and rough surface appearance. This study demonstrated the usefulness of developing extruded rich in fiber from rice and passion fruit shell flour.