Production of pectic-oligosaccharides from pomelo peel pectin by oxidative degradation with hydrogen peroxide

Oxidative depolymerization of alkali- and acid-extracted pomelo pectins was performed using 1% hydrogen peroxide (H₂O₂) with a microwave power of 550 W for 10 min. Pectic-oligosaccharides (POS) produced from the acid-extracted methyl-esterified pectin contained higher amounts of DP1 and DP2 than that from the nearly ester-free alkali-extracted pectin, and the loss of these small-size products during recovery resulted in a lower POS yield (25.0%) compared to the alkali-extracted pectin (57.7%). Degradation of the alkali-extracted pectin with 3 and 5% H₂O₂ led to a decrease in precipitable POS yield. The relative amount of large-sized POS decreased as the H₂O₂ concentration increased. An increase in the microwave power to 1100 W had no significant effect on overall yield, but the average size shifted to be lower. The results of sugar composition and identification of the degraded products with ESI-MS confirmed the existence of several POS species with different sizes and structures.