The analysis of egg wash water for the rapid assessment of microbiological quality

A total of 101 egg wash water samples from five different egg grading stations in eastern Ontario were analyzed for a variety of physical and chemical variables in an attempt to find a correlation with total bacterial counts. Temperature, pH, total chlorine, and percentage transmission at 600 nm (%T) were found to be significant variables, and a multiple regression equation was derived that accounted for 65% of the total variation. The equation was used to classify wash water samples as acceptable (< or = 10(5) cfu/mL) or unacceptable and correctly classified 77.2% of the samples. Classification of a second (validation) data set from 58 wash water samples was correctly predicted in 72% of the cases. The predictive value of the equation was especially good for those wash water samples obtained from stations that had used a chlorinated alkaline detergent, 90.4 and 100% for the modeling and validation data, respectively. Maintenance of wash water at recommended levels for temperature and pH (i.e., > or = 40 C and pH > or = 10) was insufficient to ensure bacterial numbers would be < or = 10(5) cfu/mL. Under normal operating conditions a minimum total available chlorine concentration of .45 mg/L should be maintained in wash water to ensure that bacterial numbers are kept at an acceptable level. Monitoring of temperature, pH, total chlorine, and %T will assist in maintaining wash water quality and minimize the number of samples returned to laboratories for microbiological analysis.