Green Preparation, Structural Characterization, and Antioxidant Activity of Apple Pectin Oligosaccharides Obtained by Hydrogen Peroxide Degradation

Pectin oligosaccharides are promising natural bioactive ingredients, while traditional preparation methods suffer from harsh conditions and environmental drawbacks. Herein, an eco-friendly alkaline hydrogen peroxide degradation method was applied to produce apple pectin oligosaccharides (APOSs), followed by ethanol precipitation. The structural features and antioxidant potential of APOSs were comprehensively characterized. Galacturonic acid (58.2%) was determined as the dominant monosaccharide, along with minor galactose, arabinose, and rhamnose. Sixteen oligosaccharides consisting of homogalacturonan fragments and RG-I hetero-oligosaccharides were identified using NMR, FTIR and UPLC/Q-TOF-MS. In vitro assays demonstrated excellent radical-scavenging capacities of APOSs. The DPPH and ABTS scavenging rates reached 84.6% (10 mg/mL) and 96.2% (9 mg/mL), respectively. This study provides a feasible green strategy for APOS fabrication and clarifies its antioxidant potential, supporting the industrial application of APOS as a high-efficiency natural antioxidant in functional foods.