Preliminary study on the effect of pre-freezing methods on lyophilization quality and storage stability of probiotics

Abstract

This study investigated the impact of pre-freezing techniques on the quality and storage stability of probiotics. Pediococcus acidilactici CCFM6432, Lactiplantibacillus plantarum CN2018, and Bifidobacterium breve CCFM1025 were subjected to freezing at −80 °C and −196 °C using liquid nitrogen, respectively. The results indicated that liquid nitrogen pre-freezing did not cause cell death during the freezing phase. Following lyophilization, liquid nitrogen pre-freezing did not affect the survival rates of P. acidilactici CCFM6432 and L. plantarum CN2018; however, it significantly decreased the survival rate of B. breve CCFM1025 (p < 0.05). Differential Scanning Calorimetry (DSC) analysis revealed that liquid nitrogen pre-freezing increased the melting enthalpy of the cell suspension. A linear correlation between the bacterial cell survival rate and moisture content was observed, with survival rates at the pre-freezing temperature of −196 °C slightly lower than those at −80 °C. Liquid nitrogen granulation pre-freezing enhanced the storage stability of B. breve CCFM1025. This research offers valuable insights into the potential development of pre-freezing techniques for application in the food industry to enhance the quality and storage stability of probiotics.