Survival of fluidized bed encapsulated Lactobacillus acidophilus under simulated gastro-intestinal conditions and heat treatment during bread baking

In this research, a Wurster fluidized bed coater, was used to double-coat Lactobacillus acidophilus to enhance resistance to simulated gastric conditions and increase heat stability during bread baking. The first layer of coating was Xanthan (0.5, 1 and 1.5% w/v) and alginate (0.5, 1 and 1.5% w/v). The microcapsules coated by 1% alginate showed the highest relative survival in simulated gastric conditions and was, therefore, selected as the first layer of the microcapsules. Chitosan (0.5, 1 and 1.5% w/v), and gellan (0.5, 1 and 1.5% w/v) were used for the second layer. Encapsulation efficiency decreased with increasing the level of both alginate and xanthan and microcapsule containing 1% xanthan had significantly higher (p < 0.05) encapsulation yield. In the case of acid resistance, 1% alginate in the wall matrix made significantly (p < 0.05) higher viability of the probiotic. 0.5% chitosan in the outer layer of the microcapsules caused probiotic more resistant to the heat treatment of 90 degrees C for 15 min. Probiotics population was significantly decreased in 90 degrees C heat treatment for 30 min. Moreover, results from SEM indicated that chitosan represented the smoother surface that is an essential factor to protect cells against environmental condition. Evaluation of encapsulated probiotic viability in bread showed that 1% chitosan in outer layer caused higher survivability on fresh bread and 24 h after baking. These finding indicated that the application of alginate and chitosan in the microcapsules can protect the L. acidophillus and it is considered as an effective method in probiotic bread production.