Dynamic rheological properties of Lepidium perfoliatum seed gum: Effect of concentration, temperature and heating/cooling rate

Dynamic rheological properties of Lepidium perfoliatum seed gum (LPSG) in the linear viscoelastic region were investigated as a function of concentration (1.5, 2, 2.5 and 3% w/v), temperature (5-85 degrees C) and heatingecooling rate (1, 5 and 10 degrees C/min). It was clearly observed that the gum dispersions exhibited viscoelastic properties in a given temperatures. The storage modulus (G') was always higher than the loss modulus (G '') in all concentrations and temperatures. Mechanical spectra of LPSG were classified as weak gels based on the frequency sweep, complex viscosity (eta*) and tan delta results. Moreover, G' and G '' changes were found to be dependent on concentration, temperature and heatingecooling rate. At 5 degrees C, the storage modulus increases with increase in gum concentration. Similar results were observed for 85 degrees C, except for sample containing 2.5% LPSG. Gum solutions measured at 85 degrees C had higher storage modulus compared to those evaluate at 5 degrees C. The effect of temperature on LPSG was investigated during heating and cooling. At higher gum concentrations (2.5-3%), as the temperature increased from 50 to 85 degrees C, the storage modulus started to increase. While for low LPSG concentrations, increase in temperature had no significant effect on the storage modulus. The storage modulus of 3% LPSG increased drastically by cooling the samples from 85 to 5 degrees C. This increase was much higher for samples with 1 degrees C/min cooling rate. (C) 2013 Elsevier Ltd. All rights reserved.