Effect of microencapsulation conditions on the viability and functionality of Bifidobacterium longum 51A

- Microencapsulation process by emulsification was compared with spray drying method.
- Spray drying microcapsules ensures protection against simulated GI conditions.
- Cells encapsulated by spray drying show an increased hydrophobicity profile.
- Flow cytometry is useful for detecting cell damage after microencapsulation.
- Cell plate count does not reflect the state of cell injury.

This study aimed to evaluate cell injuries in Bifidobacterium longum 51A caused by different microencapsulation processes. For this purpose, the probiotic was microencapsulated by emulsification using alginate with starch or chitosan as well as by spray drying using skim milk as the matrix. The microcapsules were characterized by atomic force microscopy, and cell viability was determined by plate count during storage (−20 °C/90 days). Under simulated gastrointestinal conditions cell injury was analysed using fluorescence of two probes followed by flow cytometry, and the hydrophobicity of cells was evaluated by bacterial adhesion to hexadecane. During storage, B. longum 51A remained above 7.51 log10 CFU g−1 in all microcapsules. However, flow cytometry showed that only microencapsulation by spray drying maintained the cells without injury and ensured viability under simulated gastrointestinal conditions. The microstructural analysis showed few cells without coating in these microcapsules. In addition, flow cytometry showed the limitation of plate count method to assess cell viability, indicating that even when injured the bacterial cells grow in culture medium. Microencapsulation by spray drying also ensured the recovery of hydrophobicity during storage. Spray drying microcapsules can be an alternative to preserve the viability and functionality of probiotics to be incorporated into foods.