Food Safety Magazine, February/March 2013

PACKAGING“Primary packaginghas a great influenceon food quality andsafety.”450/2009/EC define specific rules forthe use of new types of materials andarticles designed to actively maintain orimprove the condition of the food. Inparticular, Regulation 1935/2004 offeredfor the first time the opportunity to useactive packaging in Europe by allowingthe application of materials with agentsthat could migrate into foods. This regulationregarding all materials and articlesintended to come into contact with foodcontains general provisions on the safetyof active and intelligent packaging andsets the framework for the EuropeanFood Safety Agencyevaluation process. 2Currently, one ofthe most interestingapproaches to improvethe performance of activepackaging systemsis the development,on a laboratory scale,of hybrid organicinorganicmaterials.Two different approaches can be used:1) systems in which the active inorganicparticles are dispersed at the nanometriclevel into the polymer matrix, and 2)systems in which the inorganic particlesare embedded into the polymer matrixand act as a carrier that enables the controlledrelease of the active compoundfrom the packaging into the food.An example of the first approach isgiven by inorganic phyllosilicate claysthat can be used as support for silvernanoparticles (AgNPs) to generate a newclass of antimicrobial systems. The plateletclays, which possess intensive chargeson their surfaces, swell in water andgenerate a stable pseudo-cross-linkingnetwork that interacts and stabilizesthe AgNPs. The silver-supporting materialcan control the release kinetics ofsilver ions because of weak electrostaticinteractions, which are established withsurface platelets of montmorillonite(MMT). We have recently shown thatsilver-MMT (Ag-MMT) antimicrobialnanoparticles can be obtained by incorporatingsilver ions into natural MMT. 3These Ag-MMT nanoparticles can beembedded in bio-based polymer matricesto explicate antimicrobial activitiesagainst microorganisms. It was shownthat water uptake by the organic matrixplays a key role in the antimicrobial efficacyof the developed active films. Agarhydrogel nanocomposites, which exhibitthe highest water content uptake, werethe most active against the tested microorganisms.An example of the second approachis given by highly ordered mesoporoussilicas that have been long recognizedas very promising materials with a widerange of possible applications, such asthe capability to actas a reservoir for theaccommodation ofdrug molecules in thepharmaceutical fieldor active compoundsin the food packagingfield. 4 In fact, the wellknownpossibility ofchemically functionalizingthe pore surfaceof siliceous mesostructures with differentorganic moieties 5 constitutes a route forcontrolling drug release by diffusionunder specific conditions. When the interactionsbetween desorbing moleculesand silica pore walls are significantlystrong and/or show some kind of specificity,the release also depends on the stabilityof the complex between the functionalgroups of the drug/active compoundand those of the substrate. Thisphenomenon permits the fine-tuning ofthe release of specific molecules from agiven mesostructure by simply changingthe functional groups that are attachedto its pore walls during the process ofsynthesis. We have recently reported thatan amino-functionalized SBA-15 mesoporoussilica exerts a profound influenceover the antioxidant release of tocopherolcontained in low-density polyethylenepolymer films. 6 When tocopherol waspreincorporated into such a mesostructure,active polymer films containing thefunctionalized carrier showed a slowerantioxidant release when compared withsamples containing either free tocopherolor tocopherol loaded into a purelysiliceous SBA-15 substrate.In general, active materials already onthe market are not very widespread inEurope. This is most likely due to somedegree of diffidence of the average consumertoward these kinds of new packagingmaterials. Notwithstanding, foodcompanies, food packaging suppliersand consumers should bear in mind thatthese new concepts can be a valuable solutionto new market requirements suchas the emerging social tendency to buyfood products at longer time intervals.For this reason, it is highly desirable tocontinue developing new packaging systemsable to maintain the characteristicsof fresh food as long as possible.Future Advances of ActivePackagingThe field of food packaging can beconsidered one of the emerging applicationsof stimuli-responsive polymermaterials. They are an interesting, innovativeand challenging class of materialsthat can adapt to surrounding environmentsand regulate the transport of moleculesas a reaction to external stimuli.To sustain life and maintain biologicalfunction, nature requires selectively tailoredmolecular assemblies and interfacesthat provide a specific chemical functionand structure as well as a change in theirenvironment. Synthetic polymer systemswith very similar attributes are oftenprepared for a broad range of applicationssuch as controlled-release systems.Recently, stimuli-responsive macromolecularnanostructures have been developed;they are capable of conformationaland chemical changes upon receptionof external signals such as change in temperature,pH or chemical composition. 7These materials will permit triggering therelease of active compounds only whenstrictly needed by the system.Edible CoatingsEdible films and coatings are otherstrategies widely investigated to meetconsumer demands for more naturalfoods and environmental protection.They can be developed using agriculturalcommodities and/or wastes of industrial(continued on page 44)34 F o o d S a f e t y M a g a z i n e