Staphylococci in a whey powder plant environment: an ecological survey as a contribution to HACCP studies

Abstract

One of the necessary steps in a HACCP study is the listing of all potential hazards associated with a certain production line. Staphylococci may be listed as such when their presence in the final product is unacceptable for public health reasons. Moreover, opportunities for growth in the line or line environment and possibilities for recontamination of the product after an effective heat treatment can also be regarded as potential hazards. As insufficient data concerning the presence of staphylococci in the environment of a spray dryer of a dairy plant were available, the line environment of a whey powder plant was examined. A total of 358 samples (Rodac plates, Biotest air agar strips, swabs and residues) were taken at various places and analysed. Staphylococcus aureus was found in four samples and in only two of four main areas sampled. S. saprophyticus and S. xylosus were predominant in ‘open’ areas. In the ‘closed’, dry area, where personnel entrance and other circulation was restricted, S. haemolyticus was the most frequently isolated species. Before the study was started, the product was incidentally found to be contaminated with a few S. aureus of a specific phage type, which was not related to any isolate found in the line or the line environment. Moreover, the S. aureus isolates, which were isolated 8 months later from a site previously found to be contaminated, were of different phage types. In hygienically operated whey powder lines, staphylococci should not be of much concern. An in-depth HACCP study should, however, be carried out to determine whether critical control points exist and how they could be controlled.