The frequency of appearance of the coliform group and enterococci in the natural butter and the properties of isolated coliform bacteria were examined. 15 samples of the marketed butter 9 samples of the laboratory preparations, 15 samples of the makers, total 48 butter samples, were examined. The frequency of appearance was examined by the multiplying bacteria method using the selective medium for their bacteria.
Both modified Eijkman medium and E. C. medium were used for Escherichia coli type, Koser medium for Aerobacter aerogenes type, Koser medium added Konnyaku flake for Aerobacter group decomposing Konnyaku mannan and S. F. medium for Enterococci.
Escherichia coli type was found in two of 24 samples. One of them in the butter dilutions of them in the butter dilutions of 10
-1-10
-3, and the other in 10
-1-10
-2.
Aerobacter group, chiefly Aerobacter aerogenes type, were found even in the butter dilutions as much high as 10
-4-10
-5 in some instances, but ware detected only in dilutions of 10
-2-10
-3 in many butter products, Aerobacter group decomposing mannan, chiefly Aerobacter cloacae type, were detected in lower dilutions than in the case of Aerobacter aerogenes type, and many of them were detected in dilutions of 10
-1-10
-2.
The frequency of appearance of Enterococci was the same as that of Aerobacter group decomposing mannan in dilutions of 10
-1-10
-2.
Escherichia coli type was also isolated. In the Aerobacter group, Aerobacter aerogenes type and Aerobacter cloacae type were detected Aerobacter aerogenes type was classified as 3 types by the fermentation of adonitol and dulcitol. All Aerobacter group decomposing mannan were Aerobacter cloacae type.
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