TY - JOUR
T1 - Kinetics and thermal behaviour of the structure formation process in HMP/sucrose gelation
AU - Silva, J. A. Lopes da
AU - Gonçalves, M. P.
AU - Rao, M. A.
N1 - Funding Information:
J. A. Lopes da Silva gratefully acknowledges the financial support of the Junta Nacional de Investigacfio Cientifica e Tecnol6gica (JNICT-Lisboa, Portugal). The authors are grateful to Dr C. May (HP Bulmer Pectin, Hereford, UK), for donating the pectin sample.
PY - 1995
Y1 - 1995
N2 - The concentration and temperature dependence of the gelation kinetics of high-methoxyl pectin (HMP; 60% sucrose, pH 3) was investigated using measurements of small-amplitude oscillatory shear. The rate of gelation close to the gel point can be described as a second-order rate process using the kinetic model of Ross-Murphy (Carbohydr. Polym. 1991, 14, 281) and a critical exponent close to that predicted by the percolation approach. The modulus after a long ageing time showed a power concentration dependence with an exponent around 3.1, higher than the classical square of concentration dependence, which was probably either due to the non-equilibrium state of the HMP gels even after long ageing times, or due to the proximity of the concentration range studied to the critical gelling concentration. The gelation rate of HMP/sucrose systems is strongly dependent on the temperature. An Arrhenius relationship was applied to describe this dependence. Two different processes are proposed to explain the discontinuity observed, each one having rates with different temperature dependence. The applicable kinetics at longer times are quite different, with a lower dependence on polymer concentration and ageing temperature. A non-isothermal kinetic model was used to describe the gelation process of the HMP/sucrose system during cooling.
AB - The concentration and temperature dependence of the gelation kinetics of high-methoxyl pectin (HMP; 60% sucrose, pH 3) was investigated using measurements of small-amplitude oscillatory shear. The rate of gelation close to the gel point can be described as a second-order rate process using the kinetic model of Ross-Murphy (Carbohydr. Polym. 1991, 14, 281) and a critical exponent close to that predicted by the percolation approach. The modulus after a long ageing time showed a power concentration dependence with an exponent around 3.1, higher than the classical square of concentration dependence, which was probably either due to the non-equilibrium state of the HMP gels even after long ageing times, or due to the proximity of the concentration range studied to the critical gelling concentration. The gelation rate of HMP/sucrose systems is strongly dependent on the temperature. An Arrhenius relationship was applied to describe this dependence. Two different processes are proposed to explain the discontinuity observed, each one having rates with different temperature dependence. The applicable kinetics at longer times are quite different, with a lower dependence on polymer concentration and ageing temperature. A non-isothermal kinetic model was used to describe the gelation process of the HMP/sucrose system during cooling.
KW - Gelation kinetics
KW - Gelation time
KW - High-methoxyl pectins
UR - http://www.scopus.com/inward/record.url?scp=0028956456&partnerID=8YFLogxK
U2 - 10.1016/0141-8130(95)93514-X
DO - 10.1016/0141-8130(95)93514-X
M3 - Article
C2 - 7772559
AN - SCOPUS:0028956456
SN - 0141-8130
VL - 17
SP - 25
EP - 32
JO - International Journal of Biological Macromolecules
JF - International Journal of Biological Macromolecules
IS - 1
ER -