Degradation kinetic models and mechanism of isomaltooligosaccharides by hydroxyl radicals in UV/H2O2 system

Kinetic models and mechanism of isomaltooligosaccharides (IMOs) by hydroxyl (OH) radicals-driven degradation in ultraviolet/hydrogen peroxide system were investigated. Electron paramagnetic resonance spectra indicated that UV radiation played an important role in the steady generation of OH radicals. The OH radicals could effectively decrease the molecular weight of IMOs and significantly oxidize hydroxy group into carbonyl and carboxy groups. Main components of IMOs were separated and identified by HPAEC-PAD and UHPLC-MS/MS methods. Degradation behaviors of IMOs were well fitted to pseudo first-order kinetics. The hydrogen abstraction by OH radicals from different CH sites at pyranose ring began a cascade reaction leading to cleavage of α-glycosidic linkage or CC bonds with formation of stable uronic/aldonic acids. Degradation rate was closely influenced by the degree of polymerization (DP) of IMOs, the initial concentrations of IMOs and H2O2. The results would pave the way for free radicals-driven degradation of polysaccharides.