Viability of Lactobacillus acidophilus NCFM Howaru Dophilus during storage at refrigeration temperatures

Abstract

Abstract A strain Lactobacillus acidophilus NCFM Howaru Dophilus is a probiotic bacterium available in dairy products and dietary supplements since 1970s. Its positive health effects have been proved by many studies. This work deals with the examination of NCFM strain’s viability during its storage at stable and unstable temperature in MRS broth and ultra-pasteurized milk. In nutritionally rich environment, Lb. acidophilus NCFM was able to survive and to metabolize the media. The relevant decrease of viable cells was observed in MRS broth about 30 days after inoculation, and in milk after 21 to 45 days at both stable and unstable temperatures, respectively. The average rate of decrease of viable cells was approximately two to three times higher in experiments at unstable temperature (GrMRS,unst = −0.149 log CFU.ml−1.d−1 in MRS broth, Grmilk,unst = 0.030 log CFU.ml−1.d−1 in milk) compared with that at stable temperature (GrMRS,st = −0.079 log CFU.ml−1.d−1 in MRS broth, Grmilk,st = 0.009 log CFU.ml−1.d−1 in milk). In the MRS broth exhausted by overnight cultivation of NCFM strain the decrease of viable cells started practically immediately (Grovernigh,unst = −0.137 log CFU.ml−1.d−1). Maintenance of the culture in milk at stable temperature was proved to be the most appropriate form of its storage.