Properties of Lactic Acid Microorganisms: Long-Term Preservation Methods

Among the relevant studies on lactic acid bacteria there are projects devoted to the multienzyme complexes of starter cultures, new competitive bacterial concentrates and their use in fermented functional milk products. In fermented milk production, the process of albuminolysis has a significant impact on the consistency, taste, and smell of the product. Therefore, lactic acid bacteria with high proteolytic properties are of the greatest interest for fermented milk industry. The present research features long- term methods for preservation of the properties of lactic acid microorganisms. The experiment defined the regime parameters of combined starter lyophilisation. The results prove that fermented milk production requires high-quality starter strains. The authors developed a long-term method for preservation of properties of particular strains of lactic acid microorganisms. The method presupposes freeze-drying with the following parameters: freezing temperature – minus 25°C in a protective 5%-glycerol medium (90 minutes); the drying temperature – 30°C (6 hours); refrigerating load – 5.45 kW/m²; residual pressure – 0.6‒0.8 kPa, bed depth – 2 mm. The authors also developed the necessary documentation (No. 9225-096-02054145-2013), procedures, and formula of the fermented milk product with a combined direct application starter.