Effects of Moringa oleifera Seed Protein on the Gel Behavior and In Vitro Digestive Properties of Japonica, Indica, and Glutinous Rice Starch

This study aimed to investigate the effects of different concentrations of Moringa oleifera seed protein (MOSP) on the water holding capacity (WHC), rheological properties (viscoelasticity), textural properties, microstructure, and in vitro digestibility of japonica rice starch (JRS), indica rice starch (IRS), and glutinous rice starch (GRS). The results showed that MOSP was randomly dispersed in the starch-based gel network structure, and addition of MOSP enhanced the WHC, textural properties, and rheological properties of the gel, so as to obtain a more solid gel network structure. Both moduli (G' and G″) of MOSP-JRS gel reached up to 1.5-fold that of its control, while for MOSP-IRS gel, both reached up to 2-fold. MOSP-IRS gel exhibited a more stable network structure and higher gel strength. The MOSP-starch interactions were mediated by hydrogen bonding, with no evidence of covalent bonding, inhibiting the enzymatic hydrolysis and reducing the digestibility of the three rice starches. When the MOSP content reached 2.5%, the resistant starch (RS) content of MOSP-JRS gel increased from 16.59% to 25.98%, while the slowly digestible starch (SDS) content of MOSP-IRS and Moringa oleifera seed protein-glutinous rice starch (MOSP-GRS) gel rose from 9.47% and 4.71% to 34.36% and 18.41%, respectively. MOSP enhanced the gel strength of rice starch through hydrogen bonding and modulated its digestibility, offering a potential and alternative solution for gluten-free, low glycemic index (GI) foods.