Effects of Mixed Fermentation on Structure and Functional Properties of Dietary Fiber from Panax notoginseng Flower Residue

In this work, the Panax notoginseng flower residue was mixed fermented with the kefir grains and kombucha consortium to investigate the effects of fermentation parameters on the functional properties of the soluble dietary fiber (SDF) and insoluble dietary fiber (IDF) by single-factor and response surface experiments. The optimal fermentation conditions were as follows: the broth ratio of kefir grains and kombucha 2:1 (v/v), inoculation amount 8% (v/w), culture temperature was 28 ℃, and fermentation time 53 h. Under these optimized conditions, the fermented SDF (F-SDF) yield was 40.32%, and its functional group abundance had been significantly enhanced. For F-SDF and F-IDF, the water holding capacity (WHC), oil holding capacity (OHC), water swelling capacity (WSC), and cation exchange capacity (CEC) increased by 80.30% and 89.77%, 69.37% and 76.77%, 111.98% and 67.18%, and 58.82% and 122.22%, respectively. The adsorption capacities of glucose and sodium cholate increased by 61.18% and 72.66%, 22.50% and 22.61%, respectively. Under simulated gastrointestinal conditions, when the pH was 2.0, the adsorption capacities of cholesterol and nitrite were significantly increased by 24.77% and 20.65%, 21.48% and 19.28%; when the pH was 7.0, the adsorption capacities of cholesterol and nitrite were significantly increased by 22.67% and 29.45%, 19.27% and 24.90%, respectively. In conclusion, the mixed fermentation effectively modified the physical structure and functional properties of the dietary fiber derived from notoginseng flower residue. The results provide a theoretical basis for promoting the high-value application of notoginseng by-products.