Effects of small amounts of kappa-carrageenan on the rheology of aqueous iota-carrageenan
1992
Piculell, L. | Nilsson, S. | Muhrbeck, P.
The temperature dependence of the rheology (shear storage and loss moduli) of two ion forms (sodium and potassium) of aqueous iota-carrageenan was investigated in the presence and in the absence of small fractions (less than or equal to 10%) of added kappa-carrageenan. Both native iota-carrageenan (which already contains kappa-carrageenan as an impurity) and a sample purified by kappa-carrageenase was investigated. In either ion form, pure iota-carrageenan forms a weak gel as a consequence of its conformational transition, and the gel becomes stronger as the helical content increases. No marked ion specificity is seen in the rheology of pure iota-carrageenan. Small fractions of kappa-carrageenan, whether added or present as impurities, have no effect on the rheology of the sodium form but a large effect on the modulus of the potassium form of iota-carrageenan. The storage moduli of the potassium iota/kappa gels fall within the limits expected for a phase-separated gel structure.
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