Valorisation of starch-rich pea byproduct into cold-extruded rice analogues: Effects of processing temperature on physicochemical, functional, cooking, and in vitro digestibility properties

Abstract

The starch-rich fraction (SRF) from pea protein fractionation is a major underutilized byproduct, and its valorisation is critical for sustainable pulse processing. This study aimed to upcycle SRF into rice analogues using cold extrusion and to evaluate the effects of extrusion temperature on their nutritional, physicochemical, structural, thermal, cooking, and in vitro digestibility properties. Conventional rice was used as the control. The rice analogues developed from SRF exhibited acceptable physical properties, superior nutritional quality with significantly higher protein (9.4 – 11 %) than the control (3 %). Both extrusion conditions produced analogues with reduced crystallinity (25-27%), lower gelatinization temperatures, and shorter cooking times (2-13 min), although they exhibited slightly higher solid loss during cooking (3.3-3.7%). The extruded products also contained a higher content of resistant starch (11-15%), resulting in a lower expected glycemic index (76-79) compared to the control (85). Among the treatments, extrusion at 50 °C produced the most pronounced effects. Therefore, rice analogues developed from SRF provide a potential solution to starch-rich byproduct utilization, yielding rice with enhanced nutritional quality, shorter cooking time, and acceptable stability. Processing at moderate temperatures preserves nutritional quality and lowers eGI, while higher extrusion temperatures improve convenience but compromise nutritional and cooking stability.