Development of active packaging solutions with natural antimicrobial compounds for organic leafy greens

Increasing consumer awareness may lead to the introduction of active packaging solutions with natural compounds that do not only preserve and protect the produce, but also maintain quality by its additional antimicrobial functions. The use of active packaging relays on a steady release of volatile active compounds into the atmosphere of the package. A procedure for the development of active packaging solutions was developed for two model systems: i) unwashed, organic wild rocket (Diplotaxis tenuifolia L.) stored for 6 days at 5°C and ii) ready-to-eat, organic iceberg lettuce (Lactuca sativa L.) stored for 5 days at 4°C. The starting point for the work was in vitro testing of eugenol, carvacrol, trans-anethole, and trans-cinnamaldehyde against storage rot. All tested compounds had high antimicrobial activity in vitro. The next step was to develop sachets releasing active compounds and to test their efficacy in vivo under laboratory condition, pellets were loaded with eugenol, carvacrol, and trans-anethole and placed inside sachets in packages. Carvacrol and trans-anethole had minor effects on the microbial load. The next step was to test the efficacy of the compounds in vivo at industrial scale. Trays with organic wild rocket containing sachets at the bottom of the package showed that eugenol and trans-anethole had no significant effect on the microbial load. This result showed that further optimization of sachet placement was necessary to allow better release of active compounds into the atmosphere during storage. The experiment with sachets attached to the upper layer of packaged ready-to-eat organic iceberg lettuce demonstrated that it was not enough to improve efficacy of active packaging. The results demonstrate that the use of active packaging with natural compounds at industrial scale is very complex, and needs careful optimization before use.