Drying characteristics and some properties of spouted bed dried semi-refined carrageenan

The study was focused on the evaluation of spouted bed drying as a method for achieving dried carrageenan gels suitable for grinding, in order to obtain a final product in the form of a powder. Cubes formed from semi-refined carrageenan gels K12, K73, and their blends with carrageenan 92S (iota) were dried in a spouted bed at three temperatures: 60, 100, and 150 °C. Functional properties of the dried product were assessed in terms of density (bulk, apparent, and true), water activity, color parameters, rheological properties, and solubility. The results revealed that the decrease in the moisture ratio with time during spouted bed drying of carrageenan gels can be described by the Page model, which was characterized by satisfactorily fitting parameters such as R2, RMSE, and Ve. On the other hand, the decrease in the spouted bed volume ratio versus moisture content had linear characteristics, and depended significantly only on the kind of material. The increase in hot air temperature from 60 to 150 °C decreased the drying time for all types of carrageenan gels by ca 50%, contributing to lower equilibrium moisture content and water activity, as well as a lighter color of the dried product, apart from K73 + iota. However, drying at 100 °C provided product with the best solubility and high gelling ability. The differences in the final values of the bulk and apparent densities of dried carrageenan samples were explained, taking into account the effect of temperature and the materials' properties on the behavior of shrinkage.