Use of Counts After Preliminary Incubation to Improve Raw Milk Quality for a Denver Plant

Abstract

A Denver processing plant was dissatisfied with limited ability of Standard Plate Counts to reflect production conditions on farms. They adopted Preliminary Incubation (PI) at 13 C (55 F) for 18–20 h and reduced the maximum permissible counts in their Milk Quality Rating Program. As a result the percentage of samples with counts > 100,000/ml dropped from 23.9 in April 1973 to 0.5 in September 1974. High PI counts on tanker loads were traced to contamination from farm bulk tank outlets. This contamination was not revealed in counts without PI.