EVALUATION OF THE EXTENT AND TYPE OF BACTERIAL-CONTAMINATION AT DIFFERENT STAGES OF PROCESSING OF COOKED HAM

In an attempt to determine the composition and origin of the spoilage flora of refrigerated vacuum-packed cooked ham, the changes in microbi al numbers and types were followed along the processing line. Results revealed Lactobacillus sake and Leuconostoc mesenteroides ssp. mesente roides as the major causative agents of spoilage of sliced ham stored at 4 degrees C and 12 degrees C, due to recontamination in the cutting room. On the contrary, the progressive deterioration of whole ham und er the same storage conditions was associated with a non-identifiable group of leuconostoc-like bacteria. Except for lactic acid bacteria, n o other organism grew in vacuum packs of either sliced or whole ham. A lthough atypical leuconostocs could not be detected among isolates rec overed from freshly produced whole ham, they appeared to survive cooki ng and proliferate during storage. Neither these organisms however, no r Lact. sake and Leuc. mesenteroides were important in curing and tumb ling as carnobacteria, mainly Carnobacterium divergens, and Brochothri x thermosphacta dominated at this stage. A progressive inversion of th e ham microflora from mostly Gram-negative at the beginning of process ing to highly Gram-postive prior to cooking was noted. Listeria monocy togenes cross-contaminated ham during tumbling. However, the pathogen was always absent from the vacuum-packed product provided that heating to a core temperature of 70 degrees C occurred and recontamination du ring slicing and packing was prevented. The percentage distribution of different species of lactic acid bacteria as well as the uncommon phe notypic characteristics of some strains were discussed.