Physical quality and in vitro starch digestibility of biscuits as affected by addition of soluble dietary fiber from defatted rice bran

The increasing demand for functional foods has boosted up the food industry to produce fiber-enriched products. The purpose of this study was to investigate the effects of soluble dietary fiber from defatted rice bran (DRB) obtained through Trichoderma viride fermentation (F-SDF) on the physical properties and starch digestion characteristics of biscuits. Rheological analysis results showed that the addition of F-SDF delayed the gelatinization of starch. Texture profile analysis (TPA) results demonstrated that the addition of F-SDF reduced the hardness, springiness, cohesiveness, gumminess, chewiness and resilience of the biscuits. The scanning electron microscopy (SEM) results showed that F-SDF hindered the formation of the gluten network structure in the biscuits, making the biscuits loose. Meanwhile, X-ray diffraction (XRD) revealed the addition of F-SDF reduced the area of the crystallization zone. In addition, F-SDF led to a significant reduction of predicted glycemic index (pGI) of reformulated biscuits. Sensory evaluation results indicated that the effects of F-SDF addition on the odor, color and taste of the biscuits were relatively small, while the biscuits with highest texture and acceptability score were obtained by incorporating 6% of F-SDF in the formulation. In summary, adding the proper amount of F-SDF could improve the physical properties of the biscuits and exhibit potential to decrease the postprandial blood glucose level resulted by biscuits.