In the present study, properties of pectin from grapefruit (Citrus paradisi Macf. cv. Changshanhuyou) peel
extracted by ultrasound-assisted extraction (UP), were compared with those of pectin extracted by
conventional heating extraction (CP). UP exhibited a lower molecular weight (Mw) but more concentrated
Mw distribution than CP. Although both UP and CP were high-methoxyl pectin, UP showed
significantly lower degree of methoxylation but higher degree of acetylation. Monosaccharide composition
analysis showed that the molecular structure of UP possessed more branch chains than CP, but
little difference was observed in the chemical structures between UP and CP from FT-IR and NMR spectra
analysis. X-ray diffraction (XRD) analysis further confirmed that UP had decreased level of crystallinity
than CP. Moreover, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) indicated
UP had higher thermal stability. UP exhibited lower apparent viscosity and elasticity than CP,
showing that ultrasound affected the rheological properties of pectin. Besides, antioxidant activity and
lipase inhibitory capacity of UP significantly enhanced compared with CP