Effect of Modification on the Structure and Functional Properties of Insoluble Dietary Fiber from the Discarded Outer Leaves of Chinese Cabbage

In this study, the impacts of three modification methods on the structure and functional properties of discarded Chinese cabbage outer leaves’ insoluble dietary fiber (CIF) was examined. The results showed that modified CIF had a rough and porous surface structure, with a reduced particle size, an increased specific surface area, an increased crystallinity, and better thermal stability compared with native CIF. The most pronounced improvement in water-holding capacity, swelling capacity, cholesterol adsorption capacity and sodium cholate adsorption capacity was found for CIF subjected to high temperature/high pressure treatment, which increased by 13.08%, 151.32%, 294.98%, and 131.75% relative to CIF, respectively. Superfine grinding caused the most significant improvement in α-glucosidase inhibitory activity, which increased by 110.05% in comparison with CIF, and superfine ground CIF had the highest free radical scavenging capacity. Lactobacillus plantarum fermentation resulted in the largest improvement in oil-holding capacity, glucose adsorption capacity and α-amylase inhibitory activity, which increased by 33.13%, 118.18%, and 31.00% compared with CIF, respectively. In conclusion, all three modified CIFs showed good performance in regulating blood sugar and lipid and possessed antioxidant activity, and thus could be used as an ingredient for functional foods.