Submitted to: Journal of Food Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/30/2008
Publication Date: 9/1/2008
Citation: Du, W., Olsen, C.W., Avena-Bustillos, R., Mc Hugh, T.H., Levin, C.E., Friedman, M. 2008. Antibacterial Activity against E. coli O157:H7, Physical Properties, and Storage Stability of Novel Carvacrol-Containing Edible Tomato Films. Journal of Food Science. 73(7):M378-383. Interpretive Summary: Dietary interest in tomatoes arises from the fact that, in addition to its flavor properties, tomatoes are reported to possess numerous non-sensory beneficial nutritional and bioactive components that may also benefit human health. These include the nutrients vitamin A, vitamin C, iron, and potassium; non-nutritive dietary fiber; the antioxidative compounds lycopene, ß-carotene, and lutein; and cholesterol-lowering and immune-enhancing glycoalklaoid tomatine. Consumption of tomatoes is reported to be associated with lowered risk of cancer, heart disease, diabetes and hypertension. These considerations suggest that edible antimicrobial films prepared from tomatoes may have multiple benefits. These include protection of food against contamination by pathogenic microorganisms associated with the antimicrobial component of the film as well as nutritional and health benefits. The present study reports on an HPLC method to measure the concentrations of the plant antimicrobial carvacrol in tomato-based films prepared by two different casting methods, on the stability of carvacrol during storage of the films for 14 weeks, and on the relationship between carvacrol levels and antimicrobial activities of the films against the foodborne pathogen E coli O157:H7. It complements a related study on antimicrobial apple films that has been accepted for publication in the Journal of Agricultural and Food Chemistry. These studies facilitate optimizing effective levels of the antimicrobial in apple and tomato films against E. coli and possibly other pathogens.
Technical Abstract: The antimicrobial activity of carvacrol, the main component of oregano oil, has received increased interest due to the increase in consumption of fresh-cut produce which has resulted in frequent outbreaks of illness associated with raw fruits and vegetables. Edible films containing carvacrol are gaining importance as potential treatment to extend product shelf-life and reduce the risk of pathogen growth on food surfaces. The main objective of the present study was to evaluate the antimicrobial activities as well as the storage stabilities and physical-chemical properties of carvacrol-containing edible tomato films. The antimicrobial activities against E. coli O157:H7 as well as the stability of carvacrol were evaluated during the preparation and storage of tomato-based films made by two different casting methods, continuous casting and batch casting. Antimicrobial assays and HPLC analysis of tomato films indicated that optimum antimicrobial effects occurred with carvacrol levels of ~0.75% added to tomato pastes prior to film preparation. Carvacrol concentrations and bactericidal effect of the films remained unchanged over the storage period of up to 98 days at 5°C and 25°C. Carvacrol addition to the tomato paste used to prepare the films increased water vapor permeability of tomato films. The continuous method for casting of the films appears more suitable for large-scale use than the batch method. Carvacrol-containing edible tomato films are useful additions to our armamentarium against foodborne pathogens.