Microencapsulation of Lactobacillus reuteri DSM 17938 Cells Coated in Alginate Beads with Chitosan by Spray Drying to Use as a Probiotic Cell in a Chocolate Soufflé

The main objective of this work was to obtain microencapsulated probiotic cells in order to improve their resistance to heat stress and gastrointestinal conditions. A further aim was to obtain a potentially probiotic chocolate soufflé. Lactobacillus reuteri DSM 17938 cells were microencapsulated by spray drying in alginate matrix and further coated with chitosan. Bacterial survival after exposure to different heat treatments and simulated gastrointestinal conditions were measured to test the microcapsules. They were also dyed by using a LIVE/DEAD® BacLight™ Bacterial Viability Kit and characterized by epifluorescence microscope observation. Furthermore, a potentially chocolate soufflé was prepared using microencapsulated cells. The results indicated that alginate microcapsules did not improve acid tolerance or heat resistance in “in vitro” experiments, while they were able to protect 7% of the Lactobacillus reuteri population during the baking of a chocolate soufflé, compared to a survival rate of 1% of free cells. By contrast, the cells microencapsulated with alginate coated with chitosan showed, compared to free cells, improved acid tolerance, allowing the cell population to remain constant after 3 h in simulated gastric conditions. Moreover, the heat resistance of cells in co-cross-linked microcapsules significantly improved compared to free cells, both in “in vitro” and “in food” experiments. Microencapsulation led to a survival rate of 10% after baking a chocolate soufflé. However, the final level of bacterial cells in the product was too low to consider the chocolate soufflé as a probiotic product.