Structural and Functional Characterization of Dietary Fibers from Stropharia rugoso-annulata

Four types of dietary fibers extracted from umbrella-expanded Stropharia rugoso-annulata were focused on in this study, specifically including cap-derived soluble dietary fiber (C-SDF), stem-derived soluble dietary fiber (S-SDF), cap-derived insoluble dietary fiber (C-IDF), and stem-derived insoluble dietary fiber (S-IDF). A comprehensive analysis and comparison of the structural characteristics and functional properties of these four dietary fibers were conducted. The structural differences among these dietary fibers were compared by using scanning electron microscopy, particle size measurement, X-ray diffraction, and Fourier transform infrared spectroscopy. Additionally, their functional properties were analyzed through assessments of hydration properties, antioxidant capacity, in vitro hypoglycemic activity, and nitrite adsorption capacity. The results showed that the surface of IDF was observed to exhibit lamellar folds, demonstrating excellent hydration properties, glucose adsorption capacity, and α-glucosidase inhibitory ability. Among them, the highest water holding capacity (19.01±0.37 g/g), oil holding capacity (9.61±0.34 g/g), and glucose adsorption capacity (44.43 mg/g) were recorded for S-IDF. Besides that, the greatest swelling capacity (18.82±0.08 mL/g) and α-glucosidase inhibitory ability (53.13%) were found in C-IDF. The SDF of Stropharia rugoso-annulata was characterized by a honeycomb-like microstructure, rich polyphenol content (3.72~6.75 mg GAE/g), and a variety of infrared vibrational groups. Better antioxidant capacity, nitrite adsorption capacity, and α-amylase inhibitory ability were exhibited by SDF. Specifically, the highest antioxidant capacity (619.67 μmol TE/mL) and nitrite adsorption capacity (526.83 μg/g) were measured for C-SDF, while the most prominent α-amylase inhibitory ability (62.46%) was observed in S-SDF. In summary, distinct functional advantages were identified for each of the four types of dietary fibers extracted from the umbrella-expanded Stropharia rugoso-annulata. These fibers can be selectively utilized based on diverse needs in the food industry, providing a reference for the industrial application of inferior-quality Stropharia rugoso-annulata.