Influence of fermentation time, cryoprotectant and neutralization of cell concentrate on freeze‐drying survival, storage stability, and acid and bile exposure of Bifidobacterium animalis ssp. lactis cells produced without milk‐based ingredients

Aims:  To investigate the stability of Bifidobacterium animalis ssp. lactis VTT E-012010 (=Bb-12) during freeze-drying, storage and acid and bile exposure. The effect of harvesting time and composition and pH of the cryoprotectant on the survival was evaluated. The procedure was performed by using a milk-free culture medium and cryoprotectants to produce cells for nonmilk-based applications. Methods and Results:  Bifidobacterial cells were grown in fermenters in general edible medium for 15 or 22 h. The cell mass was freeze-dried either as non-neutralized or neutralized using sucrose, betaine or reconstituted skim milk (control) as cryoprotectants. For stability studies freeze-dried powders were stored at 37, 5 and −20°C for 2–6 months. In addition, acid and bile tolerance of the powders was tested. Sucrose-formulated B. animalis ssp. lactis preparations had an excellent stability during storage at refrigerated and frozen temperatures for 5–6 months. They also had a good survival during storage at 37°C for 2 months as well as during exposure to pH 3 and 1% bile acids. No difference was observed between 15 and 22 h grown cells or between non-neutralized and neutralized cells. Betaine proved to be a poor cryoprotectant compared with sucrose. Conclusions:  Fermentation time and neutralization of cell concentrate before freeze-drying had no impact on the storage stability and bile and acid tolerance of freeze-dried bifidobacterial cells. The nonmilk-based production protocol using sucrose as a cryoprotectant yielded powdery preparations with excellent stability in adverse conditions (storage at elevated temperatures and during acid and bile exposure). Significance and Impact of the Study:  The results indicate that it is feasible to develop nonmilk-based production technologies for probiotic cultures. This provides new possibilities for the development of nondairy-based probiotic products.