| In this research, the potential utilization of three edible and medicinal mushroom sclerotia, Pleurotus tuber-regium (Fries) Singer (PTR), Polyporus rhinocerus Cooke (PR) and Wolfiporia cocos (Schw.) Ryv. Et Gilbn, (WC) as novel dietary fibers (DF) for enhancing passive Ca absorption in the large intestine was comprehensively investigated from biochemical, physico-chemical and physiological aspects.; The in vitro mineral binding capacity of the three sclerotial TDF to five nutritionally important minerals (Ca, Mg, Cu, Fe and Zn) subjected sequentially to simulated conditions of the human stomach, small intestine and colon were investigated and compared. Apart from releasing most of their endogenous Ca (>96%) and Mg (>95%) [about half for Cu (<63%), Fe (<55%) and Zn (<60%) only], simulated gastric condition also attenuated the possible adverse binding effect of the three sclerotial TDF on the intestinal minerals by lowering their cation-exchange capacity (>20%) and removing substantial amount of their protein (>16.2%) as well as phytate contents (>58%) [mineral chelators].; Compared with the cellulose control, all three novel sclerotial TDF exhibited significantly (p < 0.05) higher in vitro fermentability by using the human faecal microflora. Nevertheless, only the WC TDF was significantly (p < 0.05) degraded [dry matter disappearance (DMD): 53.4%; organic matter disappearance (OMD): 57.4%] to produce substantial amount of total short chain fatty acids (SCFAs) [5.23 mmol/g organic matter; with a notably high molar concentration of propionate] that lowered the pH of its non-fermented residue to a slightly acidic level (5.99).; Furthermore, the effect of the three sclerotial TDF on passive Ca absorption in the large intestine was evaluated in ovariectomized (OVX) rats. Only the WC TDF groups possessed significantly (p < 0.05) higher level of caecal total SCFAs (231 mumole/caecum) that developed a slightly acidic pH (5.88) in their caecum when compared with that of the cellulose control group. The acidic environment did not only promote the ionization of the unabsorbed Ca and Mg in their caecum but also induced hypertrophy of the caecum, which eventually resulted in augmentation of caecal soluble Ca (2.56 folds) and Mg (1.23 folds) concentrations.; Based on above findings, the highly fermentable WC TDF would likely be a novel functional food ingredient for enhancing the passive Ca absorption in the large intestine. (Abstract shortened by UMI.)... |
