Production of alginate beads by emulsification/internal gelation.

Alginate microspheres were produced by emulsification/internal gelation of an alginate sol dispersed within vegetable oil, followed by a reduction in pH to release calcium from an insoluble salt. Microspheres with mean diameters ranging from 50 to 1,000 microm were obtained with standard deviations ranging from 35 to 45% of their mean value. Smooth, spherical beads were obtained with the narrowest size dispersion when using low guluronic and low viscosity alginate and a carbonate complex as calcium vector. The calcium salt must also be included within the alginate sol as a very fine powder to promote homogeneous gelation. Internal gelation was also tested with the dropping method. Observation of the beads produced revealed that the structure of the beads is more homogeneous than observed with external gelation. Shrinking is more important, although the diffusion of large molecules is faster with internal versus external gelation.