Structural and physicochemical responses of seaweed-derived insoluble dietary fiber to temperature-controlled steam explosion: A case study on Porphyra haitanensis

Developing efficient modification strategies for seaweed-derived insoluble dietary fiber (IDF) is essential for improving its functional performance. In this study, steam explosion (SE) was applied to investigate the temperature-dependent structural and functional responses of Porphyra haitanensis IDF. Moderate SE treatment within the 140 °C–160 °C interval transformed the compact IDF matrix into a looser and more porous structure, accompanied by increasing crystallinity, thermal stability, and hydrophilicity. Compared with the control, SE140 and SE160 increased water-holding capacity by 12.73% and 21.79%, swelling capacity by 36.94% and 50.45%, and oil-holding capacity by 68.13% and 28.83%, respectively ( p  < 0.05). In vitro cholesterol adsorption capacity and pancreatic lipase inhibitory activity were also enhanced. Combined structural observations and principal component analysis supported the association among moderate SE-induced structural loosening, enhanced water immobilization, improved hydration properties, and increased in vitro lipid-related functional indicators. In contrast, SE at 180 °C caused partial structural collapse and weakened the improvement in functional performance. These results suggest that moderate SE, particularly within the 140 °C–160 °C interval, may serve as a green and scalable strategy for improving seaweed-derived IDF as a functional food ingredient.