Role of Broiler Carcasses and Processing Plant Air in Contamination of Modified-Atmosphere-Packaged Broiler Products with Psychrotrophic Lactic Acid Bacteria

Some psychrotrophic lactic acid bacteria (LAB) are specific meat spoilageorganisms in modified-atmosphere-packaged (MAP), cold-stored meatproducts. To determine if incoming broilers or the production plantenvironment is a source of spoilage LAB, a total of 86, 122, and 447LAB isolates from broiler carcasses, production plant air, and MAPbroiler products, respectively, were characterized using a libraryof HindIII restriction fragment length polymorphism (RFLP)patterns of the 16 and 23S rRNA genes as operational taxonomic units innumerical analyses. Six hundred thirteen LAB isolates from the total of655 clustered in 29 groups considered to be species specific.Sixty-four percent of product isolates clustered either withCarnobacterium divergens or withCarnobacteriummaltaromaticum type strains. The third major product-associatedcluster (17% of isolates) was formed by unknown LAB. Representativestrains from these three clusters were analyzed for the phylogeny oftheir 16S rRNA genes. This analysis verified that the two largest RFLPclusters consisted of carnobacteria and showed that the unknown LABgroup consisted ofLactococcus spp. No product-associated LABwere detected in broiler carcasses sampled at the beginning ofslaughter, whereas carnobacteria and lactococci, along with some otherspecific meat spoilage LAB, were recovered from processing plant air atmany sites. This study reveals that incoming broiler chickens are notmajor sources of psychrotrophic spoilage LAB, whereas the detection ofthese organisms from the air of the processing environment highlightsthe role of processing facilities as sources of LABcontamination.