Ultrasonic degradation of Dendrobium officinale polysaccharide: Kinetics, structural modification, and its impact on...

This study systematically investigated the ultrasonic degradation of high-molecular-weight Dendrobium officinale polysaccharide (DOP) with emphasis on degradation kinetics, physicochemical alterations, antioxidant activity, and its influence on the gelatinization, rheology, and digestibility of wheat starch (WS). A kinetic model based on the midpoint chain scission mechanism accurately described the degradation process. Structural analyses confirmed that the primary chemical composition (primarily composed of mannose (72 mol%) and glucose (27 mol%)) and functional groups of DOP remained intact after ultrasonic treatment, whereas its Mw, particle size, apparent viscosity, and water holding capacity were significantly reduced. Concurrently, solubility and in vitro antioxidant activities were markedly enhanced in the degraded fractions (UDOPs). Scanning electron microscopy (SEM) revealed notable changes in the surface morphology of UDOPs. Furthermore, both DOP and UDOPs modulated the pasting, rheological, and digestive properties of WS in a molecular-weight-dependent manner. Compared to the WS group, the WS-DOP mixtures exhibited a significant increase in peak viscosity, viscoelasticity, and resistant starch content, with growth rates of 126.99%, 51.44%, and 43.83% (p < 0.05), respectively. These findings underscore the potential of ultrasonic degradation as an effective strategy to tailor the functional properties of DOP for targeted food applications, establishing an integrated paradigm for polysaccharide modification and utilization.