Physicochemical and structural properties of soluble dietary fibres in navel orange peel modified by superfine grinding and their immunomodulatory activities

The physicochemical and structural properties of water soluble dietary fibres (SDF) extracted from navel orange peel modified by superfine grinding were investigated, as well as the immunomodulatory activity in RAW264.7 cells. Results showed that superfine grinding treatment could significantly enhance the extract yield and reduce the particle size of SDF. And the water-holding capacity, swelling capacity, oil-holding capacity, nitrite adsorption capacity and total antioxidant capacity were consequently improved. Modified SDF could significantly decrease the generation of reactive oxygen species (ROS), and promoted the production of NO and some cytokines (IL-1β, TNF-ɑ, MCP-1, and IL-6) in RAW264.7 cells. The expressions of P-P65 and HO-1 in SDF-M200 and SDF-M500 were significantly up-regulated, suggesting that SDF could mildly induce macrophage activation and enhance the immune activity. These indicated that SDF modified by superfine grinding could serve as a promising candidate of immunomodulatory ingredient for functional foods.