Spices and herbal plant species have been recognized to possess a broad spectrum of active constituents that exhibit antimicrobial (AM) activity. These active compounds are produced as secondary metabolites associated with the volatile essential oil (EO) fraction of these plants. A wide range of AM agents derived from EOs have the potential to be used in AM packaging systems which is one of the promising forms of active packaging systems aimed at protecting food products from microbial contamination. Many studies have evaluated the AM activity of synthetic AM and/or natural AM agents incorporated into packaging materials and have demonstrated effective AM activity by controlling the growth of microorganisms. This review examines the more common synthetic and natural AM agents incorporated into or coated onto synthetic packaging films for AM packaging applications. The focus is on the widely studied herb varieties including basil, oregano, and thyme and their EOs.

15The migration of antimicrobial (AM) agents carvacrol, thymol and linalool from heat pressed 16 and coated starch-based packaging films into isooctane, a recommended fatty food simulant, 17 was investigated. The AM agents were effectively released into isooctane and their overall 18 release consistently obeyed first-order kinetics. When the test temperature was increased 19 from 15 to 35°C, the diffusion coefficients increased from 6.3 × 10 -13 to 12.

:  Significant interest has emerged in the introduction of food packaging materials manufactured from biodegradable polymers that have the potential to reduce the environmental impacts associated with conventional packaging materials. Current technologies in active packaging enable effective antimicrobial (AM) packaging films to be prepared from biodegradable materials that have been modified and/or blended with different compatible materials and/or plasticisers. A wide range of AM films prepared from modified biodegradable materials have the potential to be used for packaging of various food products. This review examines biodegradable polymers derived from polysaccharides and protein‐based materials for their potential use in packaging systems designed for the protection of food products from microbial contamination. A comprehensive table that systematically analyses and categorizes much of the current literature in this area is included in the review.

Thermoplastic starch (TPS) films containing relatively low [0.75 ± 0.08% (w/w)], intermediate [1.08 ± 0.04% (w/w)] and high [3.20 ± 0.29% (w/w)] levels of the antimicrobial (AM) agents carvacrol, linalool and thymol were prepared, and their physico‐mechanical and optical properties were evaluated. Addition of these AM agents to TPS film reduced the tensile strength with increasing AM agent content, with a significant effect observed at the highest AM agent concentration. The Young's modulus and elongation at break increased with increasing AM agent concentration, especially at the highest formulation concentration of AM agent. Films having a low or intermediate formulation concentration of AM agent exhibited no significant effect on their water vapour permeability, transparency and thermal properties when compared to the control film. Although scanning electron microscope imaging suggested a significant and progressive change in the surface morphologies of the films with AM agent concentration, the overall effects on the tested properties were not significant. This suggests that the direct incorporation of AM agents into TPS films did not adversely affect the films, particularly at lower AM agent concentrations. Copyright © 2013 John Wiley & Sons, Ltd.

The antimicrobial (AM) activity of starch-based films coated with linalool, carvacrol or thymol against Saccharomyces cerevisiae in vitro and/or inoculated on the surface of Cheddar cheese was investigated. In solid medium using the agar diffusion method and in experiments involving the inoculation of the microorganism on the surface of Cheddar cheese, all the films containing these AM agents in coatings demonstrated an inhibitory effect against S. cerevisiae. The results suggest that the overall inhibitory effect of linalool, carvacrol or thymol increased significantly (p ≤ 0.05) with the concentration of each of the AM agents in the film coating and that the response is linear in the concentration range of 1% to 5% (w/w) of the AM agent. Thymol had the highest AM efficacy followed by carvacrol whereas linalool had the lowest efficacy amongst the three systems. The zones of inhibition in the agar diffusion test method at 25˚C for S. cerevisiae were found to be 7.6, 7.1 and 6.1 mm for thymol, carvacrol and linalool at 1% (w/w) loading and 13.2, 12.2 and 11.2 mm at 5% (w/w) loading of the AM agents respectively. The death rates of S. cerevisiae on cheddar cheese wrapped in films coated with thymol, carvacrol and linalool and stored for up to 28 days at 15°C were found to be 0.044, 0.043 and 0.038 day -1 at 1% (w/w) loading and 0.077, 0.073 and 0.063 day -1 at 5% (w/w) loading of the AM agents respectively.