Lactobacillus casei immobilized onto montmorillonite: Survivability in simulated gastrointestinal conditions, refrigeration and yogurt.

This study evaluated the survival of Lactobacillus casei when immobilized onto montmorillonite (MMT) and sodium exchanged montmorillonite (Na-MMT) under stress conditions. The results showed that adsorption of L. casei onto MMT and Na-MMT surface reached equilibrium after 1.5h. The percentages of L. casei adsorbed onto the surfaces of MMT and Na-MMT at equilibrium were 55.3% and 83.7%, respectively. L. casei-mineral complexes were characterized by X-ray diffraction, Fourier transformed infrared and thermogravimetric analysis, indicating that L. casei cells were successfully immobilized onto MMT and Na-MMT. Characterization with scanning electron microscope showed that cells attached well to the surface of clay minerals and numerous L. casei cells were observed to form aggregates with clay mineral particles. Immobilization on MMT and Na-MMT protected L. casei from simulated gastrointestinal conditions. Immobilization preserved the counts of L. casei higher than 107CFUmL-1 throughout the storage at refrigerated conditions. Yogurts prepared with L. casei-mineral complex presented lower values for post-acidification and higher stability compared to the product prepared with the addition of L. casei in free status. The results of this study suggested the efficiency of immobilization by adsorption onto clay minerals to increase the survival of L. casei in simulated gastrointestinal conditions, refrigerated storage and yogurt.