Optimization of Ultrasound and Acid Assisted Pretreatment Combined with Drying to Improve Resistant Starch, Structural Characteristics, and Bioactive Functionality of Green Banana Flour

Abstract This study optimized combined ultrasound and acid pretreatments and drying to regulate starch digestibility, structural organization, and bioactive functionality of green banana flour (GBF). Citric acid, sodium metabisulfite, and ultrasound were optimized using central composite design (CCD) to improve resistant starch (RS) content and reduce glycemic index (GI). Optimized pretreatments were integrated with freeze, vacuum, and oven drying to evaluate their effect on flour quality. Freeze-dried treated (FDT) GBF exhibited the highest RS content (75.73%), lowest GI (36.58%), improved hydration, and oil absorbing capacity. SEM revealed a compact microstructure, while FTIR confirmed functional groups, and XRD indicated reduced crystallinity. Antioxidant capacity was highest in FDT. HPLC identified gallic acid, catechin, and chlorogenic acid as predominant phenolics. While Principal component analysis (PCA) demonstrated clear separation of treatments based on structural and functional attributes. Overall, the optimized processing approach enhances GBF’s physicochemical and nutritional properties, supporting its application in functional food and nutraceutical formulations.