Primary structure, physicochemical properties, and digestive properties of four sequentially extracted polysaccharides from Tremella fuciformis

Polysaccharides from Tremella spp. are known to have various functions and applications. To fully understand the polysaccharide compositions of fruiting body of T. fuciformis, cold water extract (CWE), hot water extract (HWE), dilute alkaline extract (ALE), and dilute acid extract (ACE) were sequentially prepared and characterized. Their physicochemical properties, chemical composition, micromorphology, and functional properties were determined. Firstly, the four extracts showed significant difference in chemical compositions. Secondly, in the structural aspect, liquid chromatographic elution curves of the extracts had only one main peak except that CWE had two peaks. Fucose, galactose (or glucose), xylose, and mannose were detected in CWE and HWE. Differently, ALE had fucose, glucose, and xylose, and ACE had only galactose and glucose, which agreed with the information obtained from Fourier transform infrared spectra. Thirdly, in the physicochemical and nutritional aspects, the thermal stability of the four extracts decreased in the order of: ACE>HWE≈ALE>CWE. HWE and ALE had similar dynamic viscoelasticity, exhibiting viscous characteristics at low frequencies and elastic characteristics at higher vibration frequencies. The four extracts were digestive-resistant after in vitro mimic experiments. This study could provide some theoretical data support for the scientific research and its application in food, medicine, and cosmetics of tremella polysaccharides.