Ultrasonic degradation effects on the physicochemical, rheological and antioxidant properties of polysaccharide from Sargassum pallidum

The aim of this study was to investigate the effects of ultrasound degradation on the physicochemical, rheological and antioxidant properties of Sargassum pallidum polysaccharides (SpPS). The results indicated that the ultrasound irradiation could significantly decrease the average molecule weight (MW), and particle size (Z(avg)) of native SpPS. The degradation pattern of SpPS was closely fitted to the first-order polymer degradation (random chain scission). The primary structure of SpPS before and after ultrasound degradation was not changed, and scanning electron microscopy (SEM) analysis showed that the morphology of SpPS was different from those of the degraded SpPS fractions. Rheological analysis indicated that the degraded SpPS solutions exhibited lower apparent viscosities than native SpPS solution at the same concentration, while the elasticity of the degraded fractions at a certain extent was enhanced. Furthermore, appropriately degraded SpPS fractions exhibited stronger DPPH and ABTS scavenging activity.