Evolution of sliced cooked ham microbiota packaged in modified atmosphere

Microorganisms colonize cooked ham (CH) packaged in modified atmosphere with a preferential growth of psychrotrophic lactic acid bacteria (LAB). Depending on the strains, the overwhelming colonization can result in a premature spoilage, characterized by pH decrease, gas and slime production, discoloration, and off-flavors formation. The LABs of 15 CH samples coming from different manufacturers were analyzed both at the beginning (T0) and at the end (Tf) of the shelf-life. Randomly selected colonies were subjected to RAPD-PCR clustering, and each biotype was taxonomically characterized through 16S rRNA gene partial sequencing. The evolution of sensorial properties was monitored by evaluation of the samples at T0 and Tf. Seven other CH samples were similarly processed when identified as flawed and withdrawn from the market before the sell-by date. The samples at the end of the shelf life and the spoiled ones shared a similar cultivable microbiota, dominated by Lactobacillus sakei, L. curvatus, and Leuconostoc carnosum. Less recurrent species were Weissella viridescens, Leuconostoc mesenteroides, Enterococcus faecalis, and Enterococcus pseudoavium. The microbiota of the flawed and unflawed (T0 and Tf) samples was further characterized by meta-taxonomic analysis. Initial population was generally represented by consortia of bacteria belonging to the order of Lactobacillales (Lactobacillus, Carnobacterium, Leuconostoc, Enterococcus, Vagococcus, Weissella, Streptococcus), Acinetobacter spp. and other Moraxellaceae, Pseudomonas spp., Bacillus, Prevotella, Weissella, Brochotrix, Vibrio rumoiensis, and Vellionella dispar. Samples that evolved into a spoiled product and samples that were delivered as flawed were often characterized by a dominant population of Lactobacillales. Among the flawed CH samples, overwhelming colonization of Brochothrix or Vibrio rumoiensis was detected.