Rheological properties of the hot-water extracted polysaccharides in Ling-Zhi (Ganoderma lucidum)

Abstract

The intrinsic viscosity, coil overlap and Mark-Houwink parameters of the hot water extracted polysaccharides from the fruit body and mycelia of Ganoderma lucidum were measured as a function of solvents and dehydration methods. Effects of ionic strength on the intrinsic viscosity, salt tolerance and chain stiffness parameters of G. lucidum polysaccharides were also characterized. It was found that when water was used as the solvent for the polysaccharides extracted from the fruit body (GLFP) and mycelium (GLMP) of G. lucidum, molecular aggregations were likely occurred to some extent. However, as DMSO was used, a less compact, more extended conformation was obtained, as indicated by the higher Mark-Houwink exponents (1.32-1.66) and lower power dependence of viscosity on concentration. Intrinsic viscosity of both GLFP and GLMP decreased with increasing ionic strength, possibly due to the presence of uronic acid groups in the polysaccharide structure. GLMP generally showed higher viscosity than GLFP, possibly due to larger molecular size. Drying method, including hot-air, vacuum, and freeze drying, did not show a significant influence on the theological properties of GLFP and GLMP in the dilute domain. Such information would be relevant during the development of functional foods containing G. lucidum polysaccharide. (C) 2006 Elsevier Ltd. All rights reserved.