Physicochemical, structural and functional properties of pomelo spongy tissue pectin modified by different green physical methods: A comparison

Pectin is a valuable bioactive ingredient, but its practical application is limited in many areas due to its high molecular weight and complex structure. In this work, the effect of different physical methods (ultra-high pressure, ultrasonic, and high-temperature cooking) on the physicochemical, structural, and functional characteristics of pomelo spongy tissue pectin (PP) were investigated. Ultra-high pressure treatment (300 MPa, 15 min) decreased the degree of esterification (DE, 4.53 %) and the degree of acetylation (DA, 2.76 %) of PP. And the PP subjected to the ultrasonic treatment (200 W, 20 min) exhibited the highest esterification degree (66.02 %), galacturonic acid content (GalA, 406.40 mg/g), and degradation enthalpy (66.93 J/g). Meanwhile, the PP treated with high-temperature cooking (HCT, 120 °C, 30 min) had the lowest acetylation degree (2.02 %), molecular weight (8.48 × 104 Da), and GalA content (254.92 mg/g). SEM and XRD results showed that the degradation effect of high temperatures on PP was more evident than other physical modification methods. Remarkably, all modified pectin solutions showed lower viscosity compared to untreated PP solution. Among these PP samples, higher antioxidant activity (103.29-134.22 mmol TE/g FRAP and 646.27-705.25 mmol TE/g ORAC values) was found in the HCT-treated PP. Moreover, the ultra-high pressure and ultrasound modified pectins revealed better emulsifying activity and emulsifying stability than unmodified PP. The results of this study indicated that the PP could be treated to achieve the desired functional application through these three physical modification methods.