Antimicrobial packaging of chicken fillets based on the release of carvacrol from chitosan/cyclodextrin films

• Fast release of carvacrol from a chitosan–cyclodextrin device
• Antimicrobial effect of carvacrol depends on the headspace concentration.
• Great retention of carvacrol by chicken proteins reduces antimicrobial activity.
• Sensorial deterioration of product limits the amount of carvacrol to be incorporated.

Chitosan/cyclodextrin films (CS:CD) incorporating carvacrol were obtained by casting, and conditioned at 23 °C and 75% relative humidity prior to being immersed in liquid carvacrol until they reached sorption equilibrium. In a previous work, the in vitro antimicrobial activity of these films was studied. In this work, active films were used to inhibit microbial growth in packaged chicken breast fillets. Samples of CS:CD films loaded with carvacrol, of different sizes and thus with different quantities of antimicrobial agent, were stuck to the aluminium lid used to seal PP/EVOH/PP cups containing 25 g of chicken fillets. These samples were stored for 9 days at 4 °C. The packages were hermetically sealed and it was confirmed that they provided an infinite barrier to carvacrol. The partition of the antimicrobial agent within the food/packaging system was analysed. The antimicrobial devices rapidly released a large percentage of the agent load, amounts that were gained by the adhesive coating of the lid and especially by the chicken fillets. The latter were the main sorbent phase, with average concentrations ranging between 200 and 5000 mg/Kg during the period of storage. The microbiota of the packaged fresh chicken fillets – mesophiles, psychrophiles, Pseudomonas spp., enterobacteria, lactic acid bacteria and yeasts and fungi – were analysed and monitored during storage. A general microbial inhibition was observed, increasing with the size of the active device. Inhibition with a 24 cm2 device ranged from 0.3 log reductions against lactic acid bacteria to 1.8 logs against yeasts and fungi. However, the large amount of antimicrobial that was sorbed or that reacted with the fillet caused an unacceptable sensory deterioration. These high sorption values are probably due to a great chemical compatibility between chicken proteins and carvacrol.