title: Dying in yoghurt: the number of living bacteria in probiotic yoghurt decreases under exposure to room temperature.
abstract: OBJECTIVE
  While probiotic bacteria are successfully used in the treatment of ulcerative colitis, the effect of commercially available probiotic products is still controversial. Here, we study whether the number of living probiotic bacteria in yoghurts is altered by an interruption of the cold chain.
  
  
  METHODS
  Three commonly available probiotic yoghurts were kept at 4°C or put at room temperature (RT) for 6 h or 24 h. An aliquot of each yoghurt was applied on Man-Rogosa-Sharpe agar and incubated at 37°C for 48 h. Colony forming units (CFU) were counted by microscopy.
  
  
  RESULTS
  The first yoghurt, containing Lactobacillus johnsonii, showed a significant decrease in CFU after 6 h of storage at RT, which was further pronounced after 24 h. The number of CFU of the second yoghurt, containing Lactobacillus GG, was also decreased after 6 h and further diminished after 24 h at RT. From the third yoghurt, containing Lactobacillus acidophilus, only 53.8% of the CFU remained after 6 h at RT; after 24 h, only about one fourth of the CFU were found.
  
  
  CONCLUSIONS
  Our data demonstrate that the number of living probiotic bacteria in yoghurt products decreases dramatically after exposure to RT. This represents an important information for consumers of such products.
authors.affiliation: Division of Gastroenterology and Hepatology, University Hospital Zürich, Zürich, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Scharl
authors.forename: Steffen
authors.initials: S
authors.lastname: Geisel
authors.forename: Stephan R
authors.initials: SR
authors.lastname: Vavricka
authors.forename: Gerhard
authors.initials: G
authors.lastname: Rogler
mesh_terms: D015169:Colony Count, Microbial; D005519:Food Preservation; D007778:Lactobacillus / Q000254:growth & development*; D050296:Microbial Viability; D019936:Probiotics; D012034:Refrigeration; D013696:Temperature; D013997:Time Factors; D015014:Yogurt / Q000382:microbiology*