Survival of Bifidobacterium longum 1941 microencapsulated with proteins and sugars after freezing and freeze drying

Five types of proteins and three types of sugars were examined for their effectiveness in protecting B. longum after freeze drying, including their acid and bile tolerance, surface hydrophobicity, retention of β-glucosidase, lactate dehydrogenase and adenosine triphosphatase. Sodium caseinate 12%, whey protein concentrate 12%, sodium caseinate:whey protein concentrate 6%:6%, skim milk 12%, or soy protein isolate 12% was combined with glycerol (3% w/v), mannitol (3% w/v) or maltodextrin (3% w/v). Fifteen emulsion systems containing sugars were obtained. Concentrated B. longum 1941 was incorporated into each emulsion system at a ratio of 1:4 (bacteria:emulsion). All the mixtures were then freeze dried. Water activity (aw) of freeze dried microcapsules was in the range of 0.30 to 0.35. WPC-CAS GLY provided high stability of bacteria (99.2%) during freezing, while high stability of cells after freeze drying and during exposure to acid and bile environment was achieved when CAS-MAN was applied (97.4%, 81.6% and 99.3%, respectively). High retention of β-glu of freeze-dried bacteria was achieved using SM-MAN as protectant (94.6%). ATPase and LDH were successfully retained by SM-GLY (94.9 and 83.6%, respectively) but there was no significant difference in protection effect using CAS-MAN (93.8 and 82.6%, respectively). Overall, milk proteins were superior to SPI and sugar alcohols provided more protection than MD.

► Protective effect of proteins and sugars on survival of Bifidobacterium was studied. ► Freeze drying was the final stage for obtaining microencapsulated Bifidobacterium. ► Casein-mannitol improved survival, acid tolerance and bile tolerance of the cells. ► Skim milk or casein added with glycerol or mannitol retained high enzyme activities. ► Skim milk or casein combined with sugar alcohols was effective lyoprotectant.