Rheological properties of Bambara groundnut (Vigna subterranea) modified starches

Physicochemical and rheological properties of modified Bambara groundnut (BGN) starches were assessed to enhance their industrial food applications. Native BGN starch (NBGNS) was chemically modified via a green chemistry grafting procedure using ascorbic acid and hydrogen peroxide as initiators to produce modified starch (MBGNS) and a starch-catechin complex (BG-SC). Morphological analysis (SEM) and powder X-ray diffraction (XRD) confirmed that native Type C crystallinity was converted into an amorphous state following modification. Proximate analysis showed that modification increased carbohydrate purity from 83.67% to 91.22% and significantly reduced moisture to approximately 8.30%, meeting industrial shelf-stability standards. Rheological assessments revealed that all BGN starch gels exhibited viscoelastic ''weak gel'' behaviour (G’ > G”) and non-Newtonian shear-thinning flow. Structural rigidity (GLVE) increased with concentration across all starch types: NBGNS (1.66–12.24 kPa), MBGNS (3.01–25.35 kPa) and BG-SC (0.07–17.02 kPa). Steady shear data fitted the Herschel-Bulkley model (R2 0.98–0.99), with yield stress for 18% gels reaching 126.03 Pa. While native gels were brittle, modified gels showed more homogeneous deformation and improved spreadability. The starch-catechin complex exhibits softer, more viscous profiles than MBGNS because catechin stabilises the internal network after initiator-induced molecular debranching. These findings establish a sustainable chemical engineering framework for transforming BGN, a climate-resilient, underutilised legume into high-performance, tailorable thickeners and stabilisers for industrial applications. This research provides the first comprehensive rheological map for BGN starch gels, offering a predictive tool for industrial scale-up and the development of clean label stabilisers.