EFFECT OF WASHING EGGS UNDER COMMERCIAL CONDITIONS ON BACTERIAL LOADS ON EGG-SHELLS

Thirty-three sample sets, each consisting of washed and unwashed eggs, and washwater were collected from 4 commercial egg grading plants in Maryland and southeastern Pennsylvania [USA]. The 4 plants used different combinations of washing compounds and sanitizing or water rinses. Bacterial loads on eggs were determined both by a surface rinse method and by a method involving evacuating and blending the shells (EB). Total plate counts at 22 and 37.degree. C were not significantly different. Surface counts on washed eggs in plants using sanitizing rinses were frequently very low (< 50/shell) and were significantly lower than in one plant using water rinse. When the sanitizer was temporarily cut off in plants using a sanitizing rinse, surface counts on washed eggs were as low as before, indicating that any beneficial effect of the sanitizer was indirect. Correlations between bacterial counts of washwater and of washed eggs were low but significant. Further examination of the data indicated that little if any contamination of eggs by washwater occurred in most cases. Bacterial counts on selective and differential agars showed generally low but variable numbers of coliforms and enterococci and substantial numbers of micrococci on the shells. Salmonellae were isolated from 2 lots of unwashed eggs and 1 of washed eggs by all the EB method.