Abstract:The effects of moisture content and water activity (aw) on the storage stability of Lactobacillus casei LC-134 (LC-134) lyophilized powder were studied. LC-134 lyophilized powders with different moisture contents and aw values were stored at -18 ℃ for 12 months and at 25 ℃ for six months, respectively. Viable cell count variation of the powders were measured regularly, and the influence of polydextrose concentration in the lyoprotectant on the moisture content and aw of the powders was explored. The results showed that during 12 months of storage at -18 ℃, no significant decrease was found in the viable cell counts of the LC-134 lyophilized powders with a moisture content of less than (5.14±0.06)?10-2 g/g or an aw value of less than 0.31±0.01. However, the viable cell count was stable at 25 ℃ during six months of storage if the moisture content was less than (3.06±0.05)?10-2 g/g or aw was less than 0.25±0.01. The addition of polydextrose could reduce the aw value of LC-134 lyophilized powders with the same moisture content. Moreover, the higher the moisture content, the more significant the effect.
