Physico-chemical properties and rheology of alginate gel beads formed with various 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 different molecular weights and M/G ratio were investigated. The results obtained showed that (1) to produce spherical beads, the product of alginate concentration 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 ionic strength influence the mechanical properties of alginate beads; (3) critical point drying and cryogenic preparation are equivalent and less disturbing methods than lyophilization for studying the structural properties of alginate beads in SEM; and (4) calcium-alginate beads are smooth and uniform whereas copper-alginate beads are rough and seem to be formed of associations of independent microgels. (C) 1999 Elsevier Science Ltd. All rights reserved.