Degradation of polysaccharides from Sargassum fusiforme using UV/H2O2 and its effects on structural characteristics

[Display omitted] •PSF could be efficiently degraded using UV/H2O2.•UV/H2O2 had a high recovery rate of total sugar and the clearance rate of protein.•Combined UV with H2O2 had a better degradation than UV or H2O2 alone.•Structural characteristic of PSF before and after UV/H2O2 treatment were studied.•PSF with UV/H2O2 treatment was easier to digest in the gastrointestinal tract. The depolymerization effect of UV/H2O2 on the polysaccharides from Sargassum fusiforme (PSF), a brown algae, were studied. The structural changes of PSF before and after UV/H2O2 treatment were analyzed, and molecular weight changes during in vitro digestion were determined. Results indicated that the molecular weight of PSF was reduced from ∼289 to ∼12.6 kDa within 2 h with UV/150 mmol/L H2O2, and the depolymerization effect of UV/H2O2 was significantly higher than that of UV or H2O2 alone. In addition, the UV/H2O2 treatment had a high recovery rate of total sugar (93.54 %) and clearance rate of protein (76.34 %). The monosaccharide composition showed that UV/H2O2 treatment could increase the mole percentage of mannose (37.44 %) and decrease the mole percentage of fucose (14.88 %). The helix-coil transition, X-ray diffraction (XRD) and atomic force microscopy (AFM) imaging showed that the UV/H2O2 treatment depolymerized PSF. Rheological studies indicated that PSF with UV/H2O2 treatment had lower viscosity. In vitro digestion showed that PSF was minimally digested with the in vitro gastrointestinal tract simulation, but PSF with UV/H2O2 treatment could be digested in the low acid environment in the simulated gastric juice, but was minimally digested with the simulated intestinal juice. This studied suggested that the preparation and application of functional PSF with low molecular weight might be beneficial.