Carvacrol-containing edible tomato films inhibit pathogenic bacteria.

We all know that tomatoes have many nutritional and bioactive components that can benefit human health. These include vitamin A, vitamin C, iron and potassium; non-nutritive dietary fiber; the antioxidative compounds lycopene, [beta]-carotene and lutein; and cholesterol-lowering and immune-enhancing glycoalklaoid tomatine.

Consuming tomatoes is believed to lessen our chances of getting cancer, heart disease, diabetes or hypertension. These considerations suggest that edible antimicrobial films prepared from tomatoes may have multiple health and safety benefits.

Carvacrol inhibits the growth of several bacteria, including E. coli and Bacillus cereus. Its low toxicity, together with a pleasant taste and aroma, suggest its use as an additive to prevent bacterial contamination in products. The antimicrobial activity of carvacrol, the main component of oregano oil, is gaining 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 could be used to extend a product's shelf life and reduce the risk of pathogen growth on product surfaces.

USDA-ARS scientists used a high-performance liquid chromatography technique to measure the concentrations of carvacrol in tomato-based films prepared by two casting methods--continuous casting and batch casting. The continuous method appears more suitable for large-scale use than the batch method. The researchers also examined the compound's stability after the films were in storage for 14 weeks. They looked at the relationship between the amount of carvacrol and the antimicrobial activity of the films against E coli O157:H7.

The scientists determined that carvacrol offered the best antimicrobial effects when ~0.75% of the compound was added to tomato pastes before the films were prepared. The carvacrol concentrations and bactericidal effect of the films did not change over a storage period of up to 98 days at 5 C and 25 C. Note that adding carvacrol to the tomato paste used to prepare the films increased the water vapor permeability of the films.

Further information. Wen-Xian Du, USDA-ARS Western Regional Research Center, Processed Foods Research, Room 1105, 800 Buchanan St., Albany, CA 94710; phone: 510-559-6148; fax: 510-559-5818; email: wen-xian.du@ars.usda.gov.

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