Nanocomposite polymer films for active packaging containing essential oils

Antimicrobial activity of spices and herbs has been known and described for several centuries. In recent years, two consumer-driven demands have arisen in the food industry. The first is the provision of fresh and natural foods requiring minimal preparation, while the second is the control of food safety. Consumer demand has renewed the use of natural food antimicrobial agents for food preservation. Essential oils (EO) and/or their components are becoming increasingly popular as natural antimicrobial agents to be used for a wide variety of purposes, including food preservation, complementary medicine and natural therapeutics. At present, essential oils are used by the flavouring industry for flavour enhancement and for their antioxidant effect, while the potential use of these oils as natural antimicrobial agents has been less explored. Recently, the antibacterial properties and potential application in foods of essential oils have been reviewed. A number of essential oil components have been registered by the European Commission for use as flavouring in foodstuffs. The flavourings registered are considered to present no risk to the health of the consumer and include amongst others carvacrol, carvone, cinnamaldehyde, citral, p-cymene, eugenol, limonene, menthol and thymol. Active packaging is one of the innovative food packaging concepts that have been introduced as a response to demands of consumers for high quality, safety and extended shelf-life of food products. Antimicrobial active packaging is being increasingly experimented because it is believed to have a significant potential in improving food safety and prolonging the shelf life of food products. The binding of antimicrobial agents directly to polymeric packaging is an exciting development, which allows industry to combine the preservative functions of antimicrobials with the protective functions of the pre-existing packaging concepts. This work is a preliminary study addressed to develop antimicrobial plastic packages by using essential oils and/or their components showing the best antimicrobial performances. The activation method used for the production of antimicrobial plastic films will be reported as inclusion method. In this method the EOs have been carried into the polymer matrix by using nanoparticles (i.e. organo-modified montmorillonite) during the extrusion process. Nanocomposite blends were prepared containing 5wt% of nanomer I.28 and 10wt% of carvacrol, citral, limonene, citronellale and thymol; the doped polymer pellets were pressed at 180 °C to obtain thin films which were subjected to mechanical characterization, morphological observation, oxygen permeability and antimicrobial activity tests. Antimicrobial tests showed that films containing carvacrol and citronellale were active against brochotrix thermosphacta, thus encouraging further investigation on this type of active packaging.