Incidence of different types of sporeforming bacteria in pasteurised market milk supplies*

A total of 51 pasteurised milk samples from different organised dairies in and around Kolkata were collected and analysed for enumerating the population of different groups of spore forming organisms. Tryptone glucose yeast extract agar was used for plating purpose and temperature time combinations of 55°±1°C for 48 h, 37°±1°C for 24 h, 22°±1°C for 3–5 d and 7°±1°C for 7–10 d were used for incubating thermophilic, mesophilic, psychrophilic and psychrotropic spore forming hacteria, respectively. The average counts of spore forming bacteria in pasteurised milk were between 1784.75 and 2908.67 cfu/ml, of which the mesophilic spore forming bacteria was highest (823.72 cfu/ml) in population. The counts of thermophilic (572.74 cfu/ml) and psychrophilic spore formers (633.13 cfu/ml) were medium in population. The psychrotropic spore forming bacterial count (88 cfu/ml) was comparatively less than that of other three groups.