In this study, Tremella fuciformis residues as raw material, dietary fibers from tremella were prepared by multiple enzymes. The structure of dietary fibers from tremella was studied by Fourier transform infrared (FTIR), X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). We analyzed their lipid-lowering properties in vitro (water holding, oil holding swelling cholesterol and sodium cholate binding capacitises) and the hypolipidemic effects in mice. The results showed that tremella dietary fibers presented the infrared absorption spectrum characteristics of polysaccharides and the characteristic diffraction peaks of cellulose type Ⅰ. SEM results indicated that the surface of insoluble dietary fiber (IDF) was porous, while the soluble dietary fiber (SDF) was relatively compact and spongy. IDF exhibited significantly higher water holding, oil holding, and swelling binding capacities than the corresponding SDF. However, SDF exhibited significantly higher viscosity than IDF. The results showed tremella dietary fibers were significant in swelling, water holding and oil holding, cholesterol and bile acids. In vivo experiment results in mice indicated that SDF has the best effect on hyperlipidemia mice than IDF and total dietary fiber (TDF). SDF showed that the total cholesterol (TC), triglyceride (TG) and low density lipoprotein cholesterol (LDL-C) contents dropped by 28.33%, 18.65%, and 48.97%, respectively, while high density lipoprotein cholesterol (HDL-C) content increased by 43.80%. Compared with the high-fat control (HCM) group, the arteriosclerosis index (AI) and liver index (LI) of the SDF group mice showed significant differences, indicating that SDF has a good auxiliary effect of lowering blood lipids. The administration of tremella fibers improved the lipid metabolism disorderly situation of hyperlipidemia mice. These results provide a reference for further research and rational development of T. fuciformis.

The effect of Tremella fuciformis polysaccharide (TFP) on the retrogradation property and aroma profile changes of tteok during storage was investigated. Results indicated that addition of TFP significantly increased the stability to thermal and mechanical shearing of starch, decreased short-term retrogradation, the hardness and the retrogradation enthalpy (ΔH) of tteok during storage, but had no significant effect on the amylopectin chain length of tteok. The possible mechanism for the retarding staling effect of TFP is related to the interaction between TFP and starch chains that interferes with the alignment of starch chains. Electronic nose and gas chromatography-mass spectrum (GC-MS) analysis results showed that the difference in the concentrations of volatile compounds and fatty acids of tteoks at different storage time gradually increased with the advancement of storage period. The addition of TFP to tteok inhibited the development of unpleasant volatile compounds, probably by delaying the oxidation and decomposition of lipids and preserving the antioxidant phenolic compounds in tteok, thus slowing down the flavor deterioration of tteok and contributing to flavor maintainace. Overall, this study could help food manufacturers to choose a high-effective and natural polysaccharide to control the retrogradation rate and flavor loss of tteok.

Allium cepa L. var. agrogatum Don (ALAP) is commonly consumed in China as well as other regions and has various beneficial health effects. A novel acidic polysaccharide (named ALAP-21) was obtained from ALAP by ultrasonic and microwave-assisted extraction and purification using DEAE-52 anion exchange and Sephadex G-100 columns. The monosaccharide composition, structural and antioxidative properties of ALAP-21 were investigated by GC–MS chromatography, FT-IR and NMR spectroscopies and three antioxidative activity tests in vitro. The results showed that ALAP-21 was a heteropolysaccharide composed of glucose, galacturonic acid, mannose, galactose, arabinose, rhamnose, xylose, fructose and glucuronic acid with a relative molar ratio of 26.282: 27.546: 11.400: 4.781: 2.467: 2.445: 3.622: 1.106: 1.753, owning (1→4)-α-D-Glcp, (1→4)-α-D-GalAp6Me3OA, (1→4)-β-D-Galp6OMe, (1→2)-α-L-Rhap, (1→4)-β-D-Manp glycosidic linkages. (1→4)-α-D-Glcp and (1→4)-α-D-GalAp6Me3OA residues might be the main components of the sugar chain backbone of ALAP-21. Furthermore, ALAP-21 exhibited high potential for DPPH radicals (82.02%), hydroxyl radicals (53.33%) and superoxide anion radicals (50.28%). These results provide a reference for further research and rational development of ALAP polysaccharides.