Rheological properties and interactions between polysaccharides in mixed carrageenan solutions

Abstract

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 (T_agg) 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 T_agg of IC because of the strong interaction with IC chain, whereas dextran increased T_agg of KC. The IC-KC solutions showed two-step increases at the almost same temperatures with T_aggs 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.