Chemical composition, structural and functional properties of insoluble dietary fiber obtained from the Shatian pomelo peel sponge layer using different modification methods

In order to improve the function of Shatian pomelo sponge layer insoluble dietary fiber (IDF), it was modified by high hydrostatic pressure (HHP, 400 MPa, 15 min), cellulose hydrolysis (CH, 0.4% cellulase, 70 min) and alkaline hydrolysis (AH, 1.4% sodium hydroxide solution, 20 min), respectively. Compared with the unmodified IDF, the molecular weight and particle size of the three modified IDFs were both decreased, while their void structure was increased. Specifically, the IDF treated with AH resulted in the smallest particle size (60.63 mu m) and a honeycomb-like void structure, which explained why AH-treated IDF showed the strongest glucose and cholesterol adsorption capacities in vitro. The contents of rhamnose, xylose, galactose and galacturonic acid in IDF were significantly increased after HHP treatment (H-IDF). Moreover, H-IDF and CH-treated IDF (C-IDF) exhibited similar capacities for oil-holding and cation-exchange. H-IDF presented the strongest swelling capacity and excellent capacity for cholesterol adsorption. Thus, HHP modified Shatian pomelo peel sponge layer IDF can not only improve the utilization of by-products, but also has potential application value as a novel ingredient in hypolipidemic and hypoglycemic foods products.