CONTAMINATION OF MILK WITH AIRBORNE MICROORGANISMS THROUGH THE VACUUM DEFOAMER

Abstract

Serratia marcescens aerosols were generated under a hood covering the filler end of a model EPCF Pure Pak milk packaging machine. When water was packaged with the machine, contamination by the test organism occurred only when the defoamer was in operation. Milk samples were obtained from the supply line to the filler bowl, the filler bowl, and the filled package in three different plants. Airborne microorganisms were collected at the same time in the vicinity of the packaging machine by liquid impingement. Following incubation at 4.5 C and 7.0 C, the bacterial types in milk samples from the filler bowl and package but not from the supply line were similar to those in the impingement fluid for two of the trials at both incubation temperatures, and for the third at 4.5 C incubation. Air pulled through the filler bowl at rates of 3,000 to 6,000 liters/min by the defoamer contaminated the milk with psychrotrophic microorganisms.