Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/1/2008
Publication Date: 3/27/2008
Citation: Du, W., Olsen, C.W., Avena-Bustillos, R.D., Mc Hugh, T.H., Levin, C.E., Friedman, M. 2008. Storage Stability and Antibacterial Activity against Echerichia coli O157:H7 of Carvacrol in Edible Apple Films made by Two Different Casting Methods. Journal of Agricultural and Food Chemistry. 56:3082-2088. Interpretive Summary: Based on the following observations, we conclude that apple films with added carvacrol hold promise for decreasing growth of pathogenic bacteria such as E. coli O157:H7 and/or for preventing microbial contamination in food applications: • Carvacrol was stable in the film for up to 7 weeks assuring antibacterial protection of coated foods during storage at 5 and 25°C. • Inhibitory zone induced by antimicrobial films increased with increasing carvacrol concentration. • Carvacrol added to apple films changed barrier and mechanical properties as well as color of films. • Method of casting films also affected carvacrol concentration and physical properties of apple films. • Addition of ~1% carvacrol to the apple puree solution used to make the films provided optimum antimicrobial effects against E. coli O57:H7. Further studies are needed to demonstrate the potential of the food-compatible edible apple films to reduce the human pathogen burden of foods. To meet this need, we are also evaluating the potential value of antimicrobial-containing apple films for use in foods.
Technical Abstract: The antimicrobial activities against E. coli O157:H7, as well as the stability of carvacrol, the main constituent of oregano oil, were evaluated during the preparation and storage of apple-based edible films made by two different casting methods, continuous casting and batch casting. Antimicrobial assays of films and HPLC analysis of film extracts following storage at 5°C and 25°C revealed that (a) optimum antimicrobial effects were apparent with carvacrol levels of ~1.0% added to the purees prior to film preparation; (b) carvacrol in the films and film weights remained unchanged over the storage period of up to seven weeks; and (c) casting methods affected carvacrol concentration, bactericidal activity, and physical properties of the apple films. Carvacrol addition to the purees used to prepare the films reduced water vapor and oxygen permeability of apple films. Our results indicate that carvacrol has a dual benefit. It can be used to both impart antimicrobial activities and to enhance barrier properties of edible films. The cited observations facilitate relating compositional and physico-chemical properties of apple puree films containing volatile plant antimicrobials to their use in foods.