Ultrasound-assisted alkali extraction of RG-I enriched pectin from thinned young apples: Structural characterization and gelling properties

RG-I (rhamnogalacturonan-I) pectin has recently gained growing interest owing to its diverse physiological activities. Nevertheless, exploration about its functional properties such as gelling and rheological characteristics is still lacking. In this study, RG-I enriched pectin was extracted from thinned young apples (Fuji) using an ultrasound-assisted alkaline method. The physical-chemical and gelling properties of the extracted pectin were investigated. The results revealed that thinned young apple pectin (TAP) was low methoxy pectin (LMP, DE = 17.94%), and rich in RG-I structural domain (86.5%). Moreover, TAP exhibited great thermal stability, high gel strength and water-holding capacity (90%). Scanning electron microscope (SEM) images demonstrated that TAP gel possessed a stable mesh-like structure characterized by small and densely packed voids. These findings provide valuable insights into the development of RG-I pectin gels and suggest that TAP extracted with the ultrasound-assisted alkaline method has significant potentials to be applied as gelling agents in the food industry.