Physicochemical properties, starch digestibility, textural properties, and sensory evaluation of plant-based noodles incorporated with defatted rice bran

Abstract

Instant noodles have been widely consumed worldwide due to their convenience. However, they are typically low in protein and dietary fiber and high in rapidly digestible carbohydrates, which negatively affect glycemic control. This study aimed to develop high-protein, fiber-enriched instant noodles by substituting defatted rice bran (DRB) for wheat flour at levels of 0%, 5%, 10%, 15%, and 20%, and to evaluate both the mixed flour and final instant noodle products in terms of physicochemical, pasting, cooking, textural, microstructural, nutritional, antioxidant, starch digestibility, and sensory properties. In the mixed flour samples, increasing DRB levels significantly increased particle size and water and oil absorption capacities while decreasing amylose content and pasting viscosities (p < 0.05). In the final instant noodles, texture parameters began to change significantly from the 5% substitution level onward, with increased hardness and decreased elasticity, springiness, and tensile strength (p < 0.05). These changes were associated with higher fiber content and disruption of the gluten network, as confirmed by scanning electron microscopy. Notably, fiber content significantly increased at 5% substitution compared to the control. At 20% DRB substitution, dietary fiber content reached a 3.7-fold increase, while carbohydrate content decreased by approximately 7% compared to the control (p < 0.05). Antioxidant activity significantly improved, as evidenced by higher total phenolic content and enhanced DPPH radical scavenging capacity, FRAP, and TEAC values (p < 0.05). At 20% DRB substitution, pGI, total starch (TS), and rapidly digestible starch (RDS) were reduced by 8.5%, 30%, and 36%, respectively, while slowly digestible starch (SDS) and undigestible starch (UDS) increased by 13% and 12%, respectively, suggesting potential benefits for postprandial glycemic control. Sensory evaluation results indicated that the formulation with the highest DRB level (20%) received good overall acceptance. The study suggests that incorporating DRB at a 5% substitution level, although slightly altering textural properties, significantly improved the nutritional profile by reducing TS and RDS, while increasing dietary fiber, SDS, UDS, and antioxidant capacity, without compromising sensory acceptability compared to the control formulation. Therefore, DRB could be considered a functional ingredient for the development of healthier instant noodle products.