The gelation temperatures of the examined formulations of P407 solutions were determined using the ‘‘Visual Tube Inversion
Method’’ [20]. Briefly, two glass vials, one containing 1 g of the
P407 solution and the other 1 g of water, were placed in a water
bath. The temperature was slowly increased and the temperature
at which the solution stopped flowing upon tilting was noted as
the gelation temperature (t1). Similarly, the temperature of the
water bath was lowered and the temperature, at which the gel
started flowing, was noted (t2). The thermo-couple of a digital thermometer
(Fluke, USA) was placed in the water tube. The mean ± SD
of t1 and t2 is reported as the critical gelation temperature (CGT).
Each measurement was repeated three times