Effects of different proteins on the structure and digestibility of complexes extruded with high amylose maize starch

Abstract

High amylose maize starch is a natural maize starch with an amylose content exceeding 50 % of the total starch. It has garnered attention for its green health benefits and widespread industrial applications. The purpose of this research is to explore the effects of different proteins on the structural properties, physicochemical properties, and in vitro starch digestibility of complexes extruded with high amylose maize starch. We use proteins (soybean protein isolate, wheat gluten, rice protein) and high amylose maize starch in co-extrusion. Extrusion significantly disrupted the microstructure of the starch granules, leading to protein denaturation, starch gelatinization, and crosslinking, forming a dense particle structure. Experimental results indicated that co-extrusion led to a transformation of the starch crystalline structure to a B + V type. The complexes formed with wheat gluten had a higher relative crystallinity, greater short-range order, and higher double-helix content, with smaller molecular volumes. The structure of the complex was more uniform, and the molecular size was more consistent. This compact structure helps resist the penetration of water and amylase, resulting in a gentler digestion curve, which promotes the slow release of glucose, making it more suitable for low GI foods.