RHEOLOGICAL STUDY INTO THE AGING PROCESS OF HIGH METHOXYL PECTIN SUCROSE AQUEOUS GELS/

The ageing process of high methoxyl pectin (HMP)/sucrose gels was foll owed at different ageing temperatures by small amplitude oscillatory e xperiments. Dynamic mechanical measurements allowed the characterisati on of the point at which the system undergoes the sol/gel transition. The HMP/sucrose system is extremely sensitive to temperature Variation during ageing, especially in the lower temperature range. The viscoel astic behaviour through the gel point changes with the ageing temperat ure, probably due to variations in mobility of the pectin chains, and consequently, in the lifetime of junction zones. Weaker pectin network s are formed under thermal conditions unfavourable to the development of hydrophobic interactions. Gel time and elastic modulus have a compl ex dependence on temperature, which could be attributed to the differe nt thermal behaviour of the intermolecular interactions that stabilise the nonpermanent cross links of these physical networks.