Inhibition of surface spoilage bacteria in processed meats by application of antimicrobial films prepared with chitosan

A study was undertaken to evaluate the feasibility of using antimicrobial f ilms, designed to slowly release bacterial inhibitors, to improve the prese rvation of vacuum-packaged processed meats during refrigerated storage. The antimicrobial films were prepared by incorporating acetic or propionic aci d into a chitosan matrix, with or without addition of lauric acid or cinnam aldehyde, and were applied onto bologna, regular cooked ham, or pastrami. A t various times during storage, packages were opened and the amounts of ant imicrobial agents remaining in the chitosan matrix were measured. Regardles s of film composition or meat product type, propionic acid was nearly compl etely released from the chitosan matrix within 48 h of application, whereas release of acetic acid was more limited, with 2-22% of the acid remaining in chitosan after 168 h of storage. Addition of lauric acid, but not cinnam aldehyde, to the chitosan matrix generally reduced the release of acetic ac id significantly (P less than or equal to 0.05) and the release was more li mited onto bologna than onto ham or pastrami. In addition, the efficacies o f the various films for inhibiting bacterial growth were tested against ind igenous lactic acid bacteria and Enterobacteriaceae, and against Lactobacil lus sakei or Serratia liquefaciens, surface-inoculated onto the meat produc ts. Whereas lactic acid bacteria were not affected by the antimicrobial fil ms under study, the growth of Enterobacteriaceae and S. liquefaciens was de layed or completely inhibited as a result of film application. Strongest in hibition was observed on drier surfaces (bologna), onto which acid release was slower, and with films containing cinnamaldehyde, as a result of its gr eater antimicrobial activity under these conditions. (C) 2000 Elsevier Scie nce B.V. All rights reserved.