Effect of microwave exposure to flaxseed on the composition, structure and techno-functionality of gum polysaccharides

Abstract

The current study aimed to explore the potential influences of microwave exposure to flaxseed (150 g samples, 700 W for 1–5 min) on the several techno-functional properties of flaxseed gum (FG), focusing on the changes in composition, surface morphology and multiscale structure. The results showed that microwave exposure to flaxseed actually resulted in evident etching effect on seed coat and favorable release of gum polysaccharides evaluated by higher yields (+51.11%, p < 0.05). The polysaccharide cross-linking and depolymerization were successively induced upon 1–5 min of microwave exposure to flaxseed, accompanying by the tremendously altered surface morphology, relative molecular weight and monosaccharide profiles of FG. Concurrently, flaxseed exposed to microwave for 1–5 min led to firstly augmenting and then weakening rheological behavior and viscoelastic properties of FG. Notably, the emulsifying potential of lamellar FG was confirmed by the dynamic light scattering, cryo-SEM imaging and Turbiscan Stability Index, relying on both the interface layer formation and movement restriction of emulsion droplets. Importantly, the dispositional retention of phenolic compounds, including lignans and specific phenolic acids ascended the antioxidant activities of FG (for DPPH: +1.55-fold, for FRAP: +2.38-fold, for ABTS: + 80.54%; p < 0.05), offset the decreasing enthalpy values, but differentiated thermogravimetric and thermogravimetric derivative curves upon microwave exposure. Notably, the removal of phenolic compounds differently affected the rheological, viscoelastic, gel and emulsifying properties of FG. Our findings elucidated that microwave exposure to flaxseed achieved to tailor the techno-functionality of FG based on the in situ structural modifications.