Extraction and Characterization of Pectic Oligosaccharide-Containing Fractions from Orange Pomace via Thermal Oxidative Degradation

This study aimed to extract and characterize pectic oligosaccharide (POS)-containing fractions from orange pomace, a byproduct of juice production, using alkaline hydrogen peroxide-assisted oxidative degradation at 90 °C for 1, 5, and 20 h (designated POS-1, POS-5, and POS-20, respectively), The resulting solutions exhibited favorable physicochemical and bioactive properties. Total soluble solids (TSS) ranged from 3.81 to 4.60%, with total phenolic content between 774,4 and 942.0 mg GAE/Land acidic pH values from 3.74 to 2.58. Molecular weight analysis revealed low-molecular-weight oligosaccharides ( degree of polymerization < 5), with their proportions increasing to 57.7%, 71.8%, and 86.6% with longer degradation times. Monosaccharide profiling identified fructose as the major sugar in POS-1 and POS-5, followed by galacturonic acid, whereas galacturonic acid dominated in POS-20. All POS samples exhibited radical scavenging activity, with IC50 values of 4.12-7.11 µg ascorbic acid equivalents/g (DPPH) and 7.14-15.23 µg ascorbic acid equivalents/g (ABTS). The fractions also showed antibacterial activity against selected Gram­positive and Gram-negative foodbome pathogens. Although the extracted solutions contained relatively low TSS and galacturonic acid - typical indicators of POS - they remained rich in bioactive oligosaccharides. This green and efficient method offers a sustainable strategy to valorize orange pomace into functional ingredients for food and nutraceutical applications.