Effect of temperature on high-methoxyl pectin gelation

High methoxyl pectin (HMP) gelation was investigated by small amplitude oscillatory experiments. The system studied was 1%HMP+60% sucrose (citrate buffer, pH 3). Time sweep experiments and mechanical spectra were performed at different temperatures between 5 °C and 60 °C. The gel time and the shear modulus have a complex dependence on temperature, which could be explained by the opposing effects of increasing temperature on both types of interactions that stabilize the HMP gels. The `final' viscoelastic behaviour of the HMP gels also changes with the ageing temperature at which the system has been submitted. Between 15-50 °C the behaviour is typical of a true gel, but for lower and higher temperatures, the behaviour changes to that of weak gels, with higher dependence on frequency for the dynamic moduli.