Micro- and nanocapsules are typically vesicular systems in which an active ingredient is confined to an aqueous or oily cavity surrounded by a single polymeric membrane. A potential application is the slow release of the active ingredient. The objective of this study was to microcapsulate probiotic strains in starch granules and to characterize the microcapsules. The probiotic, Lactobacillus rhamnosus PTCC 1637, Lactobacillus acidophilus PTCC1643, Lactobacillus casei ssp. casei PTCC 1608, Lactobacillus plantarum PTCC 1058, and Bifidobacterium bifidum PTCC 1644, were encapsulated in calcium alginate beads, acid-enzyme treated starch granules, and alginate coated starch granules with the objective of enhancing survival during exposure to the adverse conditions of the gastro-intestinal tract. All probitics were incubated in simulated gastrointestinal conditions for 0, 30, 60, 90 and 120 min. at 37 oC. The survivability of each strain was expressed as the destructive value (D-value). The alginate coated starch granules prevented reduction of all stains in simulated gastro-intestinal juice, resulting in significantly (P< 0.05) higher numbers of survivors, but there were no differences between alginate beads and starch granules (P< 0.05). After sequential incubation in simulated gastric (60 min), number of surviving cells was 6.5 log cfu mL-1 for L. acidophilus and 7.5 log cfu ml -1 for L. rhamnosus while 2.2 log cfu ml -1 was obtained for free cells. Particle size distribution was measured using laser diffraction technique. Minimum volume mean diameter was measured for starch granules capsules with 23.9 ± 0.311µm and maximum volume mean diameter was observed for alginate coated starch granules with 75.33 ± 0.209 µm. Morphology and porosity of the beads was studied by scanning electron microscopy (SEM) and the surface area was calculated using gas surface analyzer and BET equation. Glass transition temperature (Tg) of the protective substances (glucose, fructose, galactose, saccharose, lactose, maltose, manitol and soluble starch) were determined with differential scanning calorimetery (DSC) technique. Soluble starch had more protective effect for freeze dried strains. Acid production of the encapsulated strains in alginate coated starch granules was also studied. The encapsulated strains showed longer lag phase than free cells.

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