Sulfate groups position determines the ionic selectivity and syneresis properties of carrageenan systems

The salt sensitivity and selectivity feature of alpha-carrageenan (alpha-Car) were investigated and compared with kappa-carrageenan (kappa-Car) and iota-carrageenan (t-Car). These carrageenans are identified by one sulfate group on the 3,6-anhydro-D-galactose (DA) for alpha-Car, D-galactose (G) for kappa-Car and on both carrabiose moieties (G and DA) for t-Car. The viscosity and temperature, where order-disorder transition have been observed, were greater in presence of CaCl2 for alpha-Car and t-Car compared with KCl and NaCl. Conversely, the reactivity of kappa-Car systems were greater in presence of KCl than CaCl2. Unlike kappa-Car systems, the gelation of alpha-Car in presence of KCl was observed without syneresis. Thus, the position of sulfate group on the carrabiose determines the importance of counterion valency too. The alpha-Car could be a good alternative to kappa-Car to reduce the syneresis effects.

Automated summary

The salt sensitivity and selectivity of alpha-carrageenan (alpha-Car), kappa-carrageenan (kappa-Car), and iota-carrageenan (t-Car) were studied and compared. It was found that alpha-Car and t-Car had higher viscosity and temperature in the presence of CaCl2, while kappa-Car showed greater reactivity in the presence of KCl. Unlike kappa-Car, alpha-Car gelated without syneresis in the presence of KCl.