Abstract: The peel and pomace of Gannan navel orange were fermented to produce dietary fiber by mixed strains combined with two-stage temperature control in order to promote the utilization efficiency of citrus peel and pomace. The fermentation mode of inoculating mixed strains in sequence combined with two-stage temperature control was adopted. Specifically, Lactobacillus plantarum was inoculated firstly in the solid medium based on navel orange peel and pomace, and was cultured at 28 ℃ for 2 days. Then, Penicillium sp. CIs14 was inoculated in the medium containing L. plantarum, and was cultured at 28 ℃ for 5 days. The culture medium after fermentation was mixed with 1.5 times volume of sterile water and was placed in the shaker with 100 r·min^-1 speed at 45 ℃ for 24 h. The contents of soluble dietary fiber (SDF) and total dietary fiber (TDF) in the citrus peel and pomace after fermentation were more than 42.0% and 90.8% respectively, and SDF/TDF reached 46.2%. The contents of SDF, TDF and SDF/TDF were increased by 3.08 folds, 50.1% and 1.72 folds, respectively, compared with those in the original navel orange peel and pomace. The content of SDF and SDF/TDF were increased by 33.8% and 30.1%, respectively, compared with those in the navel orange peel and pomace fermented by Penicillium sp. CIs14 only at constant temperature (28 ℃). Therefore, the fermentation mode of inoculating mixed strains in sequence combined with two-stage temperature control could improve the content of SDF in navel orange peel and pomace effectively. In addition, this fermentation mode had good universality for other kinds of citrus peel and pomace to produce dietary fiber with high quality.

Key words: citrus peel and pomace, dietary fiber, mixed strains fermentation, two-stage temperature control