Preliminary study on microbeads production by co-extrusion technology

The present paper describes preliminary results on the development of a batch lab-scale co-extrusion device for the production of alginate beads as carrier for hydrophilic compounds. A dual jet of liquid core (aqueous solution of glucose or vitamin B-12 or olive oil) and liquid shell material (aqueous solution of alginates differing for guluronic to mannuronic ratio) was pumped through concentric extrusion nozzles and droplets were formed by means of a rotating fluid jet cutter. The shell of the bead was then hardened in the hardening bath containing a calcium chloride solution. Optimization of the co-extrusion plant accounts for the management of the operative conditions within the hardening unit (incubation time, molarity of the gelling agent), and for the control of the surface-tension-driven breakup of laminar jets which was managed by varying the jet cutter - hardening unit distance. Beads enriched in vitamin B-12, that were formed according to the best plant set-up, were tested for the bioactive release when stressed under thermal conditions simulating typical dairy products processes.