The influence of multi stage alginate coating on survivability of potential probiotic bacteria in simulated gastric and intestinal juice

The probiotics, Lactobacillus acidophilus PTCC1643 and Lactobacillus rhamnosus PTCC1637, were encapsulated into uncoated calcium alginate beads and the same beads were coated with one or two layers of sodium alginate with the objective of enhancing survival during exposure to the adverse conditions of the gastro-intestinal tract. The survivability of the strains, was expressed as the destructive value (decimal reduction time). Particle size distribution was measured using laser diffraction technique. The thickness of the alginate beads increased with the addition of coating layers. No differences were detectable in the bead appearance by scanning electron microscopy (SEM). The alginate coat prevented acid-induced reduction of the strains in simulated gastric juice (pH 1.5, 2 h), resulting in significantly (P < 0.05) higher numbers of survivors. After incubation in simulated gastric (60 min) and intestinal juices (pH 7.25, 2 h), number of surviving cells were 6.5 log cfu mL−1 for L. acidophilus and 7.6 log cfu mL−1 for L. rhamnosus by double layer coated alginate microspheres, respectively, while 2.3 and 2.0 log cfu mL−1 were obtained for free cells, respectively.