Abstract
The rheological properties of carrageenan gels (0.8-1.2 g/100 ml) were investigated in comparing the texture parameters, the rupture properties, the static and dynamic viscoelasticities with those of agar-agar gels. Sulfur content, intrinsic viscosity [η], melting point and transmissivity of gels were also measured so as to obtain correlation of the rheological properties.
Both carrageenan and agar-agar are polysaccharide which are extracted from Red Alagae. Although, those two kinds of hydrogels were found to be quite different in the rheological properties. The dynamic mudulus (E') and the rupture stress (Pf) of carrageenan gels were smaller than those of agar-agar gels. Intrinsic viscosity [η] and sulfur content of carrageenan were greater than those of agar-agar. It is noted the greater sulfur content of the sample, the smaller E', Pf and melting point of gel, although the relationship between the rheological properties and [η] was not clear. In a range of temperature from 10 to 50 °C, E' of agar-agar gel was almost constant. On the contrary, E' of carrageenan gels decreased rapidly between 30 and 40 °C.
Carrageenan was found to be adequate gelling agent for jelly because of the suitable cohesiveness, softness and transparence of this gel.
