Effects of temperature and concentration on the rheological properties of mucilage extracted from Pereskia aculeata Miller

Abstract

This work analyses the rheological properties of the mucilage extracted from leaves of the Pereskia aculeata Miller (HOPN) dependent of concentration and temperature. The concentrations studied were 1–5% (w/w) at temperatures 2–42 °C. The stationary shear test was performed to determine the fluid's behavior to the flow and the apparent viscosity (at 100 s−1). The oscillatory dynamic shear tests were performed by varying the deformation of 0.5% to 700% (at 1 Hz). The frequency sweep was performed by varying the frequency of 0.1 to 10 Hz (at 1%). The power and exponential models and the Arrhenius model were used to evaluate the effect of concentration and temperature, respectively. The mucilage solutions were classified as pseudoplastic and the behavior was explained by the power law. The HOPN concentration had a positive effect and temperature had a negative effect on the apparent viscosity. The linear viscoelasticity region exceeded the 1% deformation in all systems which were characterized as natural polymeric gels. Higher concentration yielded the higher mucilage deformability and the greater structural resistance. The frequency sweep showed that the mucilage with concentration of 1% at 2 °C do not have defined behavior; concentrations of 1% (12–42 °C), 2%, 3% and 4% (2 °C, 12 °C and 22 °C) were characterized as concentrated solutions and concentrations of 4% (32 °C and 42 °C) and 5% were characterized as gel.