Physicochemical and functional properties of dietary fiber from pummelo (Citrus grandis L. Osbeck) and grapefruit (Citrus paradisi Mcfad) cultivars

The contents and chemical structure of dietary fiber (DF), along with the physicochemical (water retention, water swelling and oil adsorption capacity) and functional properties (glucose adsorption, cholesterol adsorption and nitrite ion adsorption capacity) of insoluble and soluble dietary fiber (IDF, SDF) from the pulp of 5 pummelo (Citrus grandis L. Osbeck) and one grapefruit (Citrus paradisi Mcfad) cultivars were measured. The IDF, SDF and total DF (TDF) contents were 6.1-16.2, 1.8-5.66 and 7.9-22 g/100 g dw, respectively. Shatianyu (C. grandis) had the highest TDF content that was 1.37 and 2.78 times those from Guanximiyu (C. grandis) with white pulp and grapefruit, which had the second highest and the lowest TDF contents, respectively. The main monosaccharides of IDF were arabinose and glucose (68-71.3%) except grapefruit IDF. Meanwhile, arabinose, glucose and galactose were the main monosaccharides of SDF (89.5-97%). The molecular weights of SDF were in the range of 59-111 kDa. SDF and IDF from Guanximiyu with white and red pulp showed higher physicochemical properties, while those from Shatianyu and grapefruit showed slightly higher functional properties. Considering its highest DF content and middle-to high-level of physicochemical and functional properties, Shatianyu might show stronger health benefits because of its DF than other cultivars. Besides with a higher content, DF from Shatianyu also showed better physicochemical and functional properties compared with those from many other commonly consumed fruits. Therefore, pummelo, especially Shatianyu, is a good source of DF.