Physico-chemical properties and rheology of alginate gel beads formed withvarious divalent cations

The physico-chemical parameters influencing the behaviour of alginate beads have not been deeply studied in the literature. In this communication, the formation and the mechanical and structural properties of alginates with d ifferent molecular weights and M/G ratio were investigated. The results obt ained showed that (1) to produce spherical beads, the product of alginate c oncentration and intrinsic viscosity C[eta] must be higher than a threshold value and the accurate value is a function of the gelling cation type; (2) the nature of the cation, the polymer and cation concentration, and the io nic strength influence the mechanical properties of alginate beads; (3) cri tical point drying and cryogenic preparation are equivalent and less distur bing methods than lyophilization for studying the structural properties of alginate beads in SEM; and (4) calcium-alginate beads are smooth and unifor m whereas copper-alginate beads are rough and seem to be formed of associat ions of independent microgels. (C) 1999 Elsevier Science Ltd. All rights re served.