USE OF PHOTOBACTERIUM-LEIOGNATHI IN STUDIES OF PROCESS EQUIPMENT CLEANABILITY

The aim of the EC funded Project AIRI-CT-92 is to develop methods for the cleanability testing of food processing equipment. Photobacterium leiognathi ATCC 33469 has been suggested as an indicator organism in c leanability testing. Here, this bacterium was grown as a biofilm for 5 h or 24 h at room temperature on various surfaces, clean or milk-soil ed, by immersing the surfaces in luminous medium inoculated with P. le iognathi. The surfaces were then rinsed or cleaned using a CIP procedu re before the hygienic status was determined using conventional platin g, bioluminescence output and image analysis. Rinsing did not eliminat e the bacterium from the surfaces nor did the CIP procedure when 24-h biofilms were used, as was readily seen after enrichment in luminous m edium. In image analysis the biofilm showed a spotlike growth pattern which was most evident on stainless steel. The advantage of P. leiogna thi in the cleanability assessment, which is based on the natural ligh t output of the test bacterium, is that the test is easy to perform an d can be carried out without use of expensive reagents.