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 films, designed to slowly release bacterial inhibitors, to improve the preservation of vacuum-packaged processed meats during refrigerated storage. The antimicrobial films were prepared by incorporating acetic or propionic acid into a chitosan matrix, with or without addition of lauric acid or cinnamaldehyde, and were applied onto bologna, regular cooked ham, or pastrami. At various times during storage, packages were opened and the amounts of antimicrobial agents remaining in the chitosan matrix were measured. Regardless of film composition or meat product type, propionic acid was nearly completely 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 cinnamaldehyde, to the chitosan matrix generally reduced the release of acetic acid significantly (P < or = 0.05) and the release was more limited onto bologna than onto ham or pastrami. In addition, the efficacies of the various films for inhibiting bacterial growth were tested against indigenous lactic acid bacteria and Enterobacteriaceae, and against Lactobacillus sakei or Serratia liqueficiens, surface-inoculated onto the meat products. Whereas lactic acid bacteria were not affected by the antimicrobial films under study, the growth of Enterobacteriaceae and S. liquefaciens was delayed or completely inhibited as a result of film application. Strongest inhibition was observed on drier surfaces (bologna), onto which acid release was slower, and with films containing cinnamaldehyde, as a result of its greater antimicrobial activity under these conditions.