Optimization of Protective Agents for Freeze-Drying of Weisella cibaria N9 as a Potential Starter Culture

Abstract

In this study, it was aimed to determine the optimum cryoprotectant formulation for the lyophilization of Weissella cibaria N9 strain isolated from sourdough as a potential starter culture, the characterization of lyophilized culture and its storage stability. The optimum formulation of skim milk, lactose and sucrose as protective agents was determined by the Box-Behnken experimental design based on viability after lyophilization. The optimal cryoprotectant formulation was identified as 5.65% skim milk, 20% lactose and 20% sucrose for maximum cell survival (>99%). Lyophilized culture obtained by the optimum cryoprotectant formulation had acceptable physicochemical properties in terms of moisture and aw, glass transition, particle surface properties and crystal structure. The highest viability was observed at 4̊C (9.11 log cfu/g) with an inactivation rate of 3.37x10-3 day-1. The fastest cell reduction was observed at 70̊C as the result of an accelerated shelf life storage test, and protective agent effectively decreased thermal death. The culture produced by using cryoprotectant could be stored at room temperature for 18 months. Consequently, this protective agent formulation was an effective in protecting W. cibaria N9 viability during lyophilization and storage while lyophilized culture had ideal properties for powder materials, and accelerated shelf life storage test was a useful technique with certain predictability.