The objective of this work was to study the viability kinetics by a mathematical model of exponential decay of B. bifidum un-immobilized (free) and immobilized with sodium alginate under simulated gastrointestinal conditions in presence of food samples. The results demonstrated the protective effect of immobilization support in all experiments, compared to the free bacteria (p<0.05). The greater viability was observed in immobilized bacterial cells in the presence of breakfast model (14.7%), on the other hand greater viability loss of B. bifidum caused by beer and chili (0% after 30 min simulation) was observed. This study provides useful information on the kinetics of viability loss of immobilized bacterial cells through the upper gastrointestinal tract simulation and the effect of food samples on the viability of probiotic bacteria was demonstrated.