Measurement of Gelpoint Temperature and Modulus of Pectin Gels

Methods which permit the measurement of gelpoint (setting) temperature (T_gel) and rigidity modulus (G) of pectin gels were improved. Gel development on cooling was determined with an oscillatory pressure testing device capable of detecting a modulus as low as 3 Pa and strain values no greater than 5∞10^?3. Sample was set in a glass “U” tube during pressure oscillatory assay for T_gel determination, and transferred after gelling in the same tube for G modulus determination with modified Saunders-Ward apparatus. Results confirmed rheological behavior reported for these kinds of gels and compared favorably with small amplitude oscillatory measurements performed with a stress controlled rheometer using cone and plate (4°, dia = 4 cm) geometry at different frequencies (0.5 to 1.5 Hz) and cooling rates (1 to 3°C/min).