Lactobacillus rhamnosus GG encapsulation by spray-drying: Milk proteins clotting control to produce innovative matrices

A well-known probiotic strain, L. rhamnosus GG, was encapsulated by spray-drying in milk water-insoluble matrices upon reconstitution in hot water by exploiting and controlling the clotting reaction of milk proteins during the process. The feed solution, composed of probiotic bacteria and milk proteins, was or not subjected to the action of chymosin, a proteolytic enzyme. To optimize microencapsulation efficiency, different outlet air temperatures were tested (55, 70 and 85 °C). After spray-drying, small microparticles were recovered for further characterization. All drying conditions led to excellent bacterial survival rates (<0.5 log reduction) whereas only the highest outlet air temperature allowed the production of microparticles with acceptable moisture contents (<7%) to ensure storage stability. Finally, enzymatic cleavage of milk proteins by chymosin before atomization led to matrices presenting innovative functionalities when microparticles are reconstituted with water: rehydration or dispersion in cold (8 °C) or warm (40 °C) water, respectively.