Survival, Acid and Bile Tolerance, and Surface Hydrophobicity of Microencapsulated B. animalis ssp lactis Bb12 during Storage at Room Temperature

Survival, acid and bile tolerance, and surface hydrophobicity of microencapsulated Bifidobacterium animalis ssp. lactis Bb12 were studied during storage at room temperature (25 degrees C) at low water activity (0.07, 0.1, and 0.2). Two types of alginate-based systems were prepared with and without mannitol as microencapsulant of B. animalis ssp. lactis Bb12. Formation of gel beads containing cells was achieved by dropping each emulsion into CaCl2 solution; then, the beads were freeze dried. Survival, acid tolerance during 2-h exposure in de Man, Rogosa, Sharpe (MRS) broth at pH 2.0, bile tolerance during 8-h exposure in MRS broth containing taurocholic acid at pH 5.8, and retention of surface hydrophobicity were determined after freeze drying and during storage. The result showed that neither alginate nor alginate-mannitol formulation was effective in protecting B. animalis ssp. lactis Bb12 during freezing and freeze drying. The viability in alginate-mannitol and alginate formulations after freeze drying was 6.61 and 6.34 log CFU/g, respectively. Storage at low aw improved survival, acid tolerance, bile tolerance, and surface hydrophobicity retention of microencapsulated B. animalis ssp. lactis Bb12 when compared with controlled storage in an aluminum foil (with aw of 0.38 and 0.40 for alginate-mannitol and alginate formulations, respectively). Alginate mannitol was more effective than the alginate system during a short period of storage, but its effectiveness decreased during a long period of storage (80% survival at 10 wk). Nevertheless, storage of microencapsulated B. animalis ssp. lactis Bb12 in an aluminum foil without aw adjustment during 10 wk at room temperature was not effective (survival was 64% to 65%).