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Pectins with degree of methylation lower than 50% are able to gel in presence of divalent ions such as calcium. A phase diagram of a sodium pectinate (DM=28%) in wate, pH 7.4, and 20°C was established, evidencing three phases: sol, gel, and syneresis. From rheological experiments, the calcium concentration at the sol-gel transition was determined, [Ca2+]t/[COO−] ≈ 0.168, for a polymer concentration of 5.8 g/l and it was shown that this transition was accurately described by the scalar percolation theory. Under the same conditions, potentiometric studies showed that the binding of calcium ions seemed to be independent from physical state (sol or gel). Furthermore, this calcium binding decreased only slightly with the amount of added calcium, whereas the sodium one decreased sharply in the same time. By following the evolution of the 23Na NMR longitudinal relaxation time, and abrupt increase was found around [Ca2+]t[COO−]=0.182, which was close to the results of the rheological study.

Amylose is known to dissolve in water at temperatures above 130°C. The literature unanimously reports that, provided the polymer content exceeds about 1%, any solution will form a gel upon cooling. The phenomenon is attributed to liquid-liquid phase separation followed by crystallization. In the present work, gels were prepared using carefully controlled thermal histories in sealed glass tubes. The crucial parameter is the dissolution temperature T d , i.e., the maximum temperature at which the solution was heated. If T d

The aim of this study is to get a better understanding of the rheological behavior of starch-hydrocolloid mixtures under gelling and non-gelling conditions of the latter. Crosslinked waxy maize starch (CWMS) was used because it is free of amylose and crosslinking avoids granule rupture. Hence, swelled granules are dispersed in a phase containing essentially the hydrocolloid. Application of mixtures with K-carrageenan (kC) in the food industry provided further motivation to this work.