Abstract:  Sourdough was prepared with wheat flour and water with lactobacillus (Lactobacillus plantruam and Lactobacillus brevis) at the same portion (109 CFU/ml), incubated at 30℃ with the mixture of suspensions of L. plantruam and L. brevis. Beforethat, Lactobacillus was suspended in the water at 30℃. In order to measure the influence of different additives on the Lactobacillus at freezing temperature, four additives (glutanthione, fructose, sodium glutamate, and ascorbic acid) were added during freezing (-80℃) and frozen-storage (-20℃). The control sample was made without additive. The viability was measured every 10 days throughout 30 days of the frozen-storage period. The pH of the two strains before and after freezing and frozen-storage were measured by a pH meter. The viability was valued by the enumeration of CFU (colony-forming units) and the acidification activity. All additives showed a protective effect on cell viability as compared to saline solution, especially after freeze-drying procedures. Glutanthione was the most effective additives in preserving bacterial viability. After freezing and frozen-storage the viability of the strains was respectively 92.69%(10 days), 86.62%(20 days) and 84.98%(30 days). And the viability of the strains protected by sodium glutamate was respectively 86.65%(10 days), 68.35%(20 days) and 64.34%(30 days). The lag phase of the strains after using glutanthione and sodium glutamate was shorter, and the acidification activity was stronger. Moreover, the effect was better as the frozen-storage was prolonged. The research built a foundation for the development of frozen sourdough production.

Key words:  , freeze； sourdough； lactic acid bacteria； cryopreservation；