Examinations were made on measurement of psychrophilic, mesophilic and thermophilic bacteria found in milk from U.H.T. process and bottling process, by the use of maltiple tube method.
Milk samples were fortified with sterilized yeast-extr. solution and glucose solution, to give a final concentration of 0.25% and 0.5% respectiveiy, and colored by small amount of sterilized litmus solution. Then, 0.05-100ml aliquots of the samples were poured into test tubes or erlenmeyer flasks aseptically, and these materials were incubated for 2 days at 60°C for the enrichment culture of thermophile, 3 days at 37°C for mesophile and 10 days at 8°C for psychrophile.
After the enrichment culture incubation, the test tubes that gave changes in external appearance of the culture medium for thermophile were defined as thermophile positive. The test tubes that gave positive growth of bacteria on standard agar medium, that was smeared by a loopful of the enrichment culture for mesophile and incubated for 2 days at 37°C, were defined as mesophile positive. The test tubes that gave positive growth of bacteria on standard agar medium, that was smeared by a loopful of the enrichment culture for psychrophile and incubated for 5 days at 8°C, were defined as psychrophile positive designated by Standard Methods. And the test tubes that gave red colonies on C. V. T. medium, that was smeared by a loopful of the enrichment culture for psychrophile and incubated for 3 days at 21°C, were defined as psychrophile positive designated by Hucker.
Using the procedures reported in this paper, the extent of reduction of bacterial numbers by the U.H.T. processing could be determined and the mesophilic and psychrophilic contamination could be demonstrated in the bottling processes.