Mixtures of konjac glucomannan and kappa carrageeean at temperatures above and below the melting point of the kappa carrageenan helix
were studied by rheometry and calorimetry. The objective of the work was to investigate the effect of alkali deacetylation of the konjac
glucomannan on the properties of the mixed gels. It was shown that the gel storage modulus, at temperatures above the helix coil transition
for kappa carrageenan, increases with increasing deacetylation of the konjac glucomannan. Values were much higher than would be expected
for konjac glucomannan in the absence of kappa carrageenan. The ability of kappa carrageenan to promote alkali gel formation of konjac
glucomannan was attributed to a segregative interaction between the two biopolymers. It is proposed that the system is single phase but
gelation of konjac glucomannan is enhanced since this reduces thermodynamically unfavourable contacts between the two polymers. The
coil to helix transition temperature for kappa carrageenan, monitored by calorimetry, generally increased in the presence of konjac
glucomannan. An exception was at the highest degree of deacetylation when the major exotherm has a similar peak temperature to kappa
carrageenan alone. This may be because at high degrees of deacetylation the konjac glucomannan chains are self-associated to such an extent
that they are initially unable to promote the formation of kappa carrageenan helices. The increase in the modulus of mixed gels formed below
the kappa carrageenan coil to helix transition temperature also increases with alkali deacetylation. It was postulated that this reflects the
increase in strength and extent of these associations with increasing deacetylation. As deacetylation increases the gels become less elastic, as
monitored by stress relaxation, which was a further consequence of increasing association.