Effect of palmitoylated alginate microencapsulation on viability of Bifidobacterium longum during freeze-drying

• Viability of encapsulated Bifidobacterium longum by extrusion/spray processing was investigated.
• Encapsulation yield was determined after bacteria loading in alginate microbeads.
• Beads obtained by spray were the most effective in preserving bacterial viability.
• SEM analysis allowed characterizing the structure of microbeads.
• Size and chemical composition of beads were related to probiotic viability.

In the present research the viability of microencapsulated Bifidobacterium longum 15708 by extrusion and spray technique was investigated. Native (NA) and O-palmitoylated (PA) alginate were used as matrix for immobilization. Beads obtained by extrusion were characterized to assess the encapsulation yield (EY). Higher EY (67%) was found for bacteria immobilized in 3% PA. The effects of freeze drying on viability of entrapped B. longum were evaluated. Results indicated that microbeads obtained by spray were the most effective in preserving bacterial viability with a loss of viability of 2 log after 24 h as compared to extrusion beads and free cells where a loss of 2.9 and 2.75 log were respectively observed. No significant difference (P > 0.05) between NA and PA was observed. Scanning electron microscopy (SEM) analysis of beads showed globular structures and confirmed differences between the NA and PA alginates as to their appearance (porosity, fatty acid content), while the use of spray contributes to reduce the size of beads by 1/10. Present results showed that several alternatives such as beads size, alginate concentration, as well as polymer functionalization can be managed to allow probiotic viability.