Influence of temperature, pH, and ionic strength on the rheological properties of oviductus ranae hydrogels

The main rheological features of oviductus ranae (OR) hydrogels were investigated as a function of temperature, pH and ionic strength. With respect to the steady shear measurements, a reduction in viscosity was observed as the temperature increased. The flow behavior can be well described by the Herschel-Bulkley model in the down curve at a shear rate of 300 to 0 s−1, where standard error is lower than 20, and it behaved like a viscoplastic fluid. OR gels showed greater extent of thixotropy with the increase of temperature. Temperature dependence on apparent viscosity at a specified shear rate can be described by the Arrhenius model with high R2 values. The thermostability of OR hydrogels were verified by temperature sweep test, which showed that there was no phase transition observed in the temperature range of 10 to 90°C. It was found that at pH 5 to 10 and the salt concentration of 0 to 10 g/L, the OR hydrogels showed very weakly pH-dependent and salt-dependent rheological properties and dominant elastic behavior. All data indicated that OR has great potential for application as gelling and thickening agent with multiple healthy functions.   Key words: Rheological properties, oviductus ranae hydrogels, temperature, pH, ionic strength.