Factors affecting results obtained with European Community tests for pasteurized milk sampled at the heat treatment...

A total of 3000 samples of pasteurized milk taken at the heat treatment establishment over a 1-year period were examined for the presence of phosphatase and by a plate count at 30 degrees C, a coliform count at 30 degrees C, and a plate count at 21 degrees C after pre-incubation of the sample for 5 days at 6 degrees C, performed as prescribed in EC Directive 85/397/EEC. Samples were also examined for presence of Listeria species. Of 2690 samples (1713 from small dairies and 977 from large commercial premises) received at 4 degrees C or less, 96 (3.6%) has a plate count at 30 degrees C exceeding 30,000 organisms per ml, 608 (22.6%) contained 1 or more coliforms per ml, and in 1327 (49.3%) the pre-incubated count exceeded 100,000 organisms per ml. Thirty two samples from 23 dairies contained phosphatase. Listeria species were detected in 25 samples; only three of these strains were identified as Listeria monocytogenes. Results were analysed to determine relationships between factors which might affect test results. Samples from small dairies showed significantly higher coliform counts and pre-incubated plate counts than did those from large commercial premises. They were also more likely to contain phosphatase or Listeria species. Samples were significantly more likely to contain coliforms when taken in the July-September quarter or if received in glass containers.