抄録
The relationship between the environment within a milk plant and contamination of the produced milk with psychrophilic bacteria (PB) was analyzed in a plant where the UHT system of pasteurization was carried out.
1. The raw milk used contained about 108 PB. No PB were detected from any sample of sampling-cock milk or surge-tank milk immediately after collection or at 7 days of storage at 5 to 7°C. Samples of bottled milk were found to harbor 101 PB even immediately after collection.
2. Contamination was hardly observed in any machine after routine rinsing and disinfection. Exceptionally, the filling valve was proved to have been contaminated remarkably. Even a sample collected at it 4 hours after the beginning of operation contained 101 to 102 PB, which belonged to the genera Pseudomonas and Micrococcus. An adequate sanitary control was effective to reduce the contamination to a great extent.
3. No PB were detected at all from samples collected from the washing bottle or the cap.
4. The atmosphere within the plant harbored 10, to 102 PB, which belonged mostly to Pseudomonas.
5. Rather marked contamination was recognized at the fingers and clothes of employees, the floor of the plant, the conveyer, the hood of the bottling machine, and the frames of windows. Many organisms of Pseudomonas and Micrococcus were detected from the fingers and clothes of employees and the floor of the plant.
6. These results seem to indicate that the PB harbored by bottled milk are derived from the filling valve, the atmosphere of the plant, and such environmental conditions of the plant closely related to these as
