Viability of Lactobacillus Acidophilus and Lactobacillus Bulgaricus Cultures Stored at Various Temperatures

Summary 1.Milk cultures of L. acidophilus have been stored at refrigerator temperatures for several days without causing any marked reduction in the number of living organisms. 2.Less reduction in numbers of L. acidophilus occurred at refrigerator temperature, 9°C. (48°F.) or even at 0°C. (32°F.), than occurred at 37°C. (99°F.). 3.There was little difference in viability between organisms in acidophilus milk kept several days at refrigerator temperature, 9°C. (48°F.), and at 22°C. (72°F). 4.Judging from the results obtained at 9° and 0°C. it seems probable that cultured milk could be held at the usual storage temperatures of 4.4°C. (4°F.) or below for several days without greatly affecting the number of viable acidophilus organisms. 5.The various strains of L. acidophilus examined reacted in a similar manner to the different storage temperatures. 6.The strain of L. bulgaricus examined reacted to the storage temperatures in a manner similar to L. acidophilus. 7.The stock cultures of L. acidophilus and the recently isolated fecal strain used in the experiments were alike in their reactions to the storage temperatures. 8.Results of one acidophilus commercial broth culture indicated that refrigerator storage was also preferable to storage at room temperatures for that product. 9.Stock cultures of L. acidophilus whether old or recently isolated strains, remained viable when held in the refrigerator and transferred once in 4 to 6 weeks or longer. In one case a sealed tube of a recently isolated fecal strain stored at refrigerator temperatures for one year was viable when removed.