MICROENCAPSULATION OF PROBIOTIC BACTERIA IN XANTHAN-CHITOSAN POLYELECTROLYTE COMPLEX GELS
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In recent years, increasing evidence indicating numerous health benefits associated with the intake of probiotic bacteria has created a big market of probiotic foods worldwide. However, maintaining high numbers of viable cells in probiotic food products during the shelf life of the product and during gastrointestinal transit is a challenge. The goal of this research is to develop a novel microencapsulation system using xanthan gum and chitosan polyelectrolyte complex gels in order to protect the probiotic cells against adverse environmental conditions, and to increase their recovery rates. The extrusion method was used to form the xanthan-chitosan microcapsules.The effects of initial polymer concentration and chitosan solution pH on the crosslinking density of the capsule network were investigated by swelling studies and modulated differential scanning calorimetry (MDSC) analysis. Once the capsule formulations resulting in a highly crosslinked network structure were determined, P. acidilactici cells were successfully encapsulated using these formulations. Efforts were made to study the release kinetics of probiotic cells from these capsules in gastrointestinal conditions. Cell release was found to be negligible in simulated gastric juice. In simulated intestinal conditions, the release was relaxation controlled and complete cell release was achieved in at least 5 hours. After exposure to simulated gastric fluid (pH=2.0), encapsulation with xanthan gum and chitosan provided up to six-log and four-log preservation of the freeze-dried probiotic cells over free suspending cells for 1 and 2 hours, respectively. These results suggest that xanthan-chitosan capsules have a good potential for delivery of probiotic cells to the intestines in high numbers where the cells can release and colonize to benefit the consumer.