The Effect of Different Cryoprotectants on the Survival Rate of Freeze-dried Lactic Acid bacteria (LAB) Powder for Cucumber Fermentation

Lyophilization, or freeze-drying, is a new methodology for cucumber fermentation that operates at low temperatures to preserve nutritional value and taste and delays the product’s deterioration. The aim of this study was to determine the effectiveness of different cryoprotectants on the survival rate for fermenting cucumbers using freeze-dried lactic acid bacteria (LAB) powder.

Mixtures of freeze-dried LAB powder with cryoprotectants (skim milk, sucrose, maltodextrin, lactose, glucose, and a mix of skim milk and sucrose) were prepared using two different ratios, namely, 1:2 and 1:10. The freeze-drying process started with freezing at -80°C for 3 to 5 hours, primary drying at -50°C for 24 hours, and secondary drying at -45°C for 2 hours. Then, the survival rate was determined in terms of physicochemical quality and sensory evaluation.

The moisture content of the freeze-dried powder ranged from 2.21% to 5.43% and 2.28% to 5.6% and water activity was between 0.153-0.283 and 0.163-0.268 for the 1:10 and 1:2 ratios, respectively. There was no significant difference in pH, total acidity, reducing sugar, total soluble solids, and salt content and the sensory evaluation was acceptable. Skim milk proved to be the most effective cryoprotectant, yielding a survival rate of approximately 70% (70.07% for the 1:10 ratio and 70.01% for the 1:2 ratio) after 24 hours of storage at 4°C.