Encapsulation of Lactobacillus rhamnosus GG in double emulsions: Role of prebiotics in improving probiotics survival during spray drying and storage

The protective effect of solid fat on probiotics to reduce heat damage during spray drying was revealed in previous study. However, the direct dispersion of fresh cells in the thermo-protectants did not encapsulate the probiotics in the oil phase, but dispersed in the water phase. Therefore, this study aims to improve the protective effect of solid fat to probiotics during spray drying by encapsulating Lactobacillus rhamnosus GG (LGG) in double emulsion (W/O/W) containing solid fat. In addition, various prebiotics were added in W/O/W as wall materials, and their ability of improving the vitality of probiotics was evaluated by combining spray drying and re-culture. The results of fluorescence microscope and scanning electron microscope demonstrated the successful encapsulation of LGG in double emulsions during spray drying, which increased the survival rate from 43.23% to 65.16% while improved the integrity of the subcellular structure. In terms of prebiotic effects, the microcapsules of W/O/W + inulin showed the lowest water activity and higher glass transition temperature, leading to the best survival of LGG during storage in all tested formulations, while W/O/W + FOS had the best proliferation-promoting in re-culture due to the fact that LGG consumed more FOS than other prebiotics during re-culture. Therefore, the current study has provided valuable information for the selection of carriers and wall materials in improving the viability of probiotics during spray drying.