Storage stability and antibacterial activity against Escherichia coli O157:H7 of carvacrol in edible apple films made by two different casting methods

The antimicrobial activities against Escherichia 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 high-performance liquid chromatography (HPLC) analysis of film extracts following storage up to 49 days at 5 and 25 degrees C revealed that (a) optimum antimicrobial effects were apparent with carvacrol levels of similar to 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 7 weeks, and (c) casting methods affected carvacrol concentration, bactericidal activity, physicochemical properties, and colors of the apple films. Carvacrol addition to the purees used to prepare the films reduced water vapor and oxygen permeability of apple films. The results indicate that carvacrol has a dual benefit. It can be used to both impart antimicrobial activities and enhance barrier properties of edible films. The cited observations facilitate relating compositional and physicochemical properties of apple puree films containing volatile plant antimicrobials to their use in foods.