Rheological properties and interactions between polysaccharides in mixed carrageenan solutions

The possibility of phase separation in the mixture of iota-carrageenan (IC) and kappa-carrageenan (KC) was elucidated by comparing rheological properties for carrageenan mixtures. In temperature sweeping experiments, lambda-carrageenan (LC) chain slightly lowered the aggregation temperature (Tagg) of IC and KC in the mixture solutions of IC-LC and KC-LC, respectively, by obstructing the aggregation. On the other hand, dextran chain largely lowered the Tagg of IC because of the strong interaction with IC chain, whereas dextran increased Tagg of KC. The IC-KC solutions showed two-step increases at the almost same temperatures with Taggs in single component solutions of IC and KC. This exhibits independent aggregations of IC and KC chains in the mixture and suggesting the phase separation in the IC-KC solution. In the time courses of G', the IC-LC solution showed increases of G' by local aggregation of IC chain and by growing of aggregation of IC chain through the obstructive LC chains. The IC-dextran mixture solution showed a depressed increase of G' caused by a strong interaction between IC and dextran. The time courses of G' for the IC-KC solution showed two-step increases suggesting the induced aggregation of KC chains by the aggregation of IC chains.