Impact of Freeze-drying Conditions on the Functional Properties of Probiotic Lactic Acid Bacteria and Methods to Assess Their Viability

Fermented dairy products contain probiotic lactic acid bacteria (LAB), which are well known for their positive health effects such as enhancing host immunity and modifying the gut microbiota. Freeze-drying (lyophilization) is the favored technique for conserving these microorganisms. However, this presents significant obstacles to their viability and functionality. Therefore, we examined the influence of cryoprotectants and freeze-drying conditions on the shelf life and functional characteristics of LAB. Current advances in freeze-drying techniques for the preservation of probiotic lactic acid bacteria (LAB) from fermented dairy foods are discussed in this review. Freeze-drying processes need to be optimized to preserve the viability, functionality, and shelf life of probiotic bacteria. Cryoprotectant formulations, freeze-drying conditions, and their impact on probiotic properties, metabolic activity, and LAB survival were also reviewed. It also shows cryoprotectant effectiveness towards certain probiotics, the effect of freeze-drying treatment on the functional and metabolic characteristics of LAB, and finally explores methodological improvements towards assaying probiotic effectiveness following freeze-drying.