Survivability of probiotics encapsulated in alginate gel microbeads using a novel impinging aerosols method

Encapsulation of probiotic bacteria in cross-linked alginate beads is of major interest for improving the survivability in harsh acid and bile environment and also in food matrices. Alginate micro beads (10–40 μm) containing the probiotics Lactobacillus rhamnosus GG and Lactobacillus acidophilus NCFM were produced by a novel technique based on dual aerosols of alginate solution and CaCl2 cross linking solution. Extruded macro beads (approximately 2 mm diameter) produced by the conventional method and micro beads produced by novel aerosols technique offered comparable protection to L. rhamnosus in high acid and bile environment. Chitosan coating of micro beads resulted in a significant increase in survival time of L. rhamnosus from 40 to 120 min in acid condition and the reduction in cell numbers was confined to 0.94 log over this time. Alginate macro beads are more effective than micro beads in protecting L. acidophilus against high acid and bile. Chitosan coating of micro beads resulted in similar protection to L. acidophilus in macro beads in acid and extended the survival time from 90 to at least 120 min. Viability of this organism in micro beads was 3.5 log after 120 min. The continuous processing capability and scale-up potential of the dual aerosol technique offers potential for an efficient encapsulation of probiotics in very small alginate micro beads below sensorial detection limits while still being able to confer effective protection in acid and bile environment.

Research Highlights
► Novel technique involving dual aerosols of alginate and CaCl2 solutions form alginate micro beads (10–40 μm), encapsulating the probiotics L. rhamnosus GG and L. acidophilus NCFM.
► Comparison of micro and macro beads showed similar resistance in acid and bile environment for L. rhamnosus. Alginate macro beads were more effective than micro beads in protecting L. acidophilus NCFM against acid and bile tolerance.
► Chitosan coating showed best survivability of micro beads in both strains in acid and bile environment.