Extraction pH modulates structural, functional, and antioxidant characteristics of banana (Musa spp.) flower polysaccharides.

Banana flower is an underutilized agricultural by-product and a potential source of functional polysaccharides. In this study, the influence of extraction pH (2-12) on the structural and functional properties of banana flower polysaccharides (BFPs) was evaluated. The extraction yield increased significantly from 7.64% at pH 2 to 14.04% at pH 12. In contrast, acidic and near-neutral conditions better preserved the total sugar content, molecular weight (16.90-18.53 kDa), degree of esterification, galactose, and arabinose-rich regions. Strong alkaline extraction promoted de-esterification, reduction of neutral sugar-rich domains, and molecular depolymerization, yielding more soluble fractions with lower molecular weight and improved emulsifying activity. FTIR and NMR (1H, 13C, COSY, and HSQC) analyses confirmed the arabinogalactan-rich structural configuration of the polysaccharides, including the presence of uronic acid and rhamnose residues, while monosaccharide analysis revealed significant variations in composition across different extraction pH conditions. Functional analysis showed that acidic to near-neutral extracts exhibited higher viscosity, thermal stability, and emulsion stability, whereas alkaline extracts showed higher solubility and emulsifying activity. Antioxidant activity also varied with extraction pH, with acidic extracts showing stronger ABTS+· scavenging and ferric reducing antioxidant power, while the pH 12 fraction showed increased DPPH scavenging activity relative to pH 10. PCA confirmed clear relationships between extraction pH, molecular characteristics, and functional properties. These results demonstrate that extraction pH is an effective factor for modulating the properties of banana flower polysaccharides for different food applications.