SPORICIDAL EFFECT OF DISINFECTANTS ON BACILLUS-CEREUS ISOLATED FROM THE MILK PROCESSING ENVIRONMENT

The sporicidal efficacy of sodium hypochlorite and a combination of pe racetic acid and hydrogen peroxide on Bacillus cereus spores isolated from the milk processing environment was examined using the European S uspension Test and by a surface disinfection test on stainless steel a nd rubber, The results of the laboratory tests were compared with fiel d trials in a milking installation. In general, it was difficult to ob tain consistent results, as the repeatability and reproducibility of t he tests were found to vary according to the test strain, spore suspen sion preparation, disinfectant test solution, organic load, contact ti me and temperature. The sporulation medium used to obtain spores influ enced the sporicidal effect considerably. To overcome this problem a s tandard method for preparation of spore suspensions should be pl escri bed. The various disinfectants were move effective in suspensions than on surfaces and in field trials. For the suspension tests SE values r anging from 1.0 to 3.0 were reached within 10 min at 50 degrees C, dep ending on the disinfectant used Sodium hypochlorite-based pr oducts we re most effective. The activity on spores on surfaces and in field tri als was limited. In surface rests reductions of 0.4-0.8 were observed within 10 min at 50 degrees C depending on the type of surface. The SE values obtained for rubber were lower compared with stainless steel. The decrease in spore levels found in the milking installation was com parable with the surface experiments, i.e. 0.4-1.0. It is important to develop standard test procedures to assess the sporicidal efficacy of disinfectants used in food hygiene. Surface tests should be included to reflect the in-use conditions more closely and minimum standards sh ould be determined for both suspension tests and surface tests. Copyri ght (C) 1996 Elsevier Science Ltd