Chemical Composition and Some Rheological Properties of Mesona Blumes Gum

Abstract

A gum was extracted from the leaves of Liangfen Cao ( Mesona Blumes), the extraction yield was 29.36%. The crude gum contains 9.74% protein, 30.89% ash, 2.98% crude fibre and 42.19% total sugar (w/w). Monosaccharide components of the gum were mainly galactose, glucose, arabinose and uronic acid with mole ratios of 3.1:2.3:2.3:1.4, respectively. Minerals in the ash were mainly 40.26mg/g sodium, 10.57mg/g potassium, 1.42mg/g magnesium and 2.81mg/g calcium. Molecular weight of the two fractions of the gum were 16,264 and 7,372 Da, respectively. The intrinsic viscosity of the gum was 91.01 mL/g in distilled water at 25°C. Its rheological properties were dependent on shear rate, gum concentration, sugar, temperature, pH, and salt. The gum exhibited pseudoplastic behaviour with shear rate increment. The apparent viscosity increased with the increase of the gum concentration, also increased with the sugar addition and varied according to pH, the highest viscosity was reached at pH 10.0 and the lowest at pH 6.0. Decrease of apparent viscosity was observed with increase of temperature. The activation energy of 10% (w/w) gum was 17.58kJ/mol. The apparent viscosity decreased with Na + addition and also with the addition of [Ca ++ ]<1%, while it increased with the addition of [Ca ++ ]> 1% (w/w).