Comparative study of the germs counting in milk onto the "standard" agar plates and the milk- tryptone-glucose agar, and incubated at temperatures of 32 to 37oC

Abstract

The comparative study of about 398 samples of pasteurized milk planted on standard agar and Tryptone-glucose milk agar, incubated at 32°C. and 37°C, led to the following conclusions: 1. An increase in count was observed in 100 per cent of the samples when planted on Tryptone-glucose milk agar, instead of standard agar, both incubated at 32°C; 2. Incubation at 32°C. in combination with the use of Tryptone-glucose milk agar, resulted in increases in plate count of considerably greater magnitude than were obtained by the use of the agar and incubation at 37°; 3. The differences between the average of standard agar and Tryptone-glucose-milk-agar, at 37, and between the average of standard agar and milk agar, at 32°C, show very clearly that this difference is real and not occasional, thus proving the 'I'ryptone-glucose-milk-agar to be a more convenient medium for the growth of the germs contained in miIk than the standard agar. This growth is increased when there is used for the incubation of the plates, a temperature of 32° instead of 37°C.