A Comparative Study of the Rheological Behavior of Solutions of the Chitin-Glucan Complex from the Fruit Bodies of Armillaria mellea in Acetic and Hydrochloric Acids

Abstract

Objective: The rheological properties of the chitin-glucan complex (CGC) in aqueous solutions of hydrochloric and acetic acids were studied. The CGC sample was isolated from the fruit bodies of the honey mushrooms (Armillaria mellea), biotechnologically obtained from an easily renewable plant raw material. Methods: The flow behavior of the solutions of the chitin-glucan complex with a concentration of 1, 5, and 10 wt % in hydrochloric acid and of 1, 3, and 5 wt % in acetic acid was studied by the method of rotational viscometry in the shear rate range of 10 to 1000 s^–1 at temperatures from 20 to 50°C. Results and Discussion: The values of the rheological coefficients of the Ostwald de Waele power-law equation were determined. Viscosity anomalies indicating non-Newtonian flow behavior were revealed. The high viscosity of the solutions may be due to the presence of an internal supramolecular structure in the solutions of the chitin-glucan complex. The predominantly pseudoplastic nature of the rheological behavior of the studied solutions was shown. The flow index in this case varies from 0.18 to 0.79 for the solutions of the chitin-glucan complex in hydrochloric acid and from 0.01 to 0.47 for those in acetic acid with a concentration of 3 to 5 wt %. The pseudoplastic flow mechanism for such solutions can be explained by the destruction of the internal structure of the solution with increasing shear load. The dilatant nature of the flow of 1 wt % solutions of CGC in acetic acid at a shear rate of 10 to 100 s^–1, with the flow index ranging from 1.28 to 1.57, was also revealed. Conclusions: Dilatant behavior may be explained by the predominance of the processes of the formation of a new internal structure in the solution over those of the destruction of the existing structure in the solution at a low concentration of the chitin-glucan complex. The influence of temperature on the rheological behavior of the solutions is strongly distorted by the contribution from other factors.