59. Studies in the Bacteriology of Low-Temperature Pasteurisation. I. The Significance of Heat-Resisting Organisms in Raw Milk Supplies

Abstract

In the course of routine bacteriological examinations of milk carried out at one of the United Dairies pasteurising depots during the past three years, a remarkable lack of constant relationship between the numbers of colonies reported on the 1/10, 1/100 and 1/1000 dilution plates, when standard agar (the Ministry of Health formula) was used, has been observed. When, however, standard agar, enriched with 0·5 per cent, milk, has been used as a plating medium, many of the discrepancies between different dilutions of the same milk have disappeared.