A COMPARISON OF THE BACTOSCAN-8000S TO 3 CULTURAL METHODS FOR ENUMERATION OF BACTERIA IN RAW-MILK

The bacteriological load of bulk tank raw milk samples was determined using the Bactoscan (BSN) 8000S and three cultural methods: standard p late count (SPC), spiral plate count (SPC) and plate loop count (PLC). A total of 3640 milk samples (2918 natural and 722 spiked) were analy zed. The repeatability of each system was assessed at critical cut-off counts of log(10) 4.0 and log(10) 5.0. In descending order, kappa val ues of within-system-agreement (repeatability) at log(10) 4.0 were: SP C=0.87, SPC=0.70, BSN=0.67 and PLC=0.42. Descending kappa values at lo g(10) 5.0 were: BSN = 0.96, SPC = 0.95, PLC = 0.84 and SPC = 0.78. BSN results demonstrated good correlation with the three methods: SPC (r = 0.79), PLC (r = 0.72) and SPC (r = 0.73). These results suggest that the rapid and automated Bactoscan 8000S could provide a reasonable al ternative to the three cultural methods for enumeration of bacteria in bulk tank raw milk when counts fall within the instruments specified applicable range of log(10) 4.0-log(10) 5.477. (C) 1997 Canadian Insti tute of Food Science and Technology. Published by Elsevier Science Ltd .