Regulation of molecular structure and functional performance of Porphyra haitanensis soluble dietary fiber via...

Steam explosion (SE) at different temperatures was applied to modify the structural and functional properties of soluble dietary fiber (SDF) from Porphyra haitanensis. SE treatment at 140 °C promoted partial depolymerization, reduced molecular weight, and increased the SDF yield (by 123.75%), together with significant increases in galactose (by 56.95%), galacturonic (by 66.86%), and glucuronic acids (by 73.84%) (p < 0.05). Meanwhile, SE-treated P. haitanensis SDF showed a looser and more porous-like microstructure, accompanied by changes in hydration-related behavior. These structural changes were associated with increases in water-holding, swelling, and oil-holding capacities, as well as glucose and cholesterol adsorption capacities and inhibitory activities against α-amylase, α-glucosidase, and pancreatic lipase. In contrast, SE treatment at 180 °C was associated with partial structural reorganization and less pronounced functional improvements. Overall, controlled SE temperature can provide a green and efficient strategy for enhancing the physicochemical and biological functionalities of seaweed-derived SDF.