Encapsulation of probiotic bacteria by extrusion and in vitro and morphological study of the obtained particles

Technologies that can protect microorganisms from adverse conditions in processing, storage and passage through the gastrointestinal tract have been studied. The aim of this study was to encapsulate probiotic bacteria, to evaluate their viability and quality during shelf life, under gastrointestinal simulation conditions and during thermal behavior, and to characterize the particles obtained through physicochemical and morphological analyzes. The encapsulation was performed by extrusion technique, with 1% sodium alginate solution and 0.1 M calcium chloride solution, using the microorganisms L. acidophilus, L. rhamnosus and B. bifidum individually. In vitro tests to simulate passage through the gastrointestinal tract (mouth, stomach, duodenum and ileum) were performed on the day of manufacture of the probiotic capsules and with the free microorganism. Shelf life was performed every fifteen days from zero to 60 days by bacterial counting of Lactobacillus sp. and Bifidobacterium sp. in MRS agar medium, and the other physicochemical analyzes were performed after 24 hours of production and morphology after lyophilization of the capsules. The average size of the produced wet capsules was 1800 µm and morphological analyzes confirmed the presence of microorganisms inside the particles and not only on the wall. The tests showed that the extrusion encapsulation process was efficient to protect probiotic cells during the simulated passage through the gastrointestinal tract, and also protected the microorganisms during exposure to temperatures up to 50 ºC. The study indicated that the capsules produced with L. acidophilus presented higher probiotic viability, and the shelf life ended with 45 days of storage, because on day 60 they showed mold growth. The capsules produced presented positive results to be added in food products.