Development of silver based antimicrobial films for coating and food packaging applications

Abstract

or stiff materials (bottles, tanks, caps, etc) in any imaginable size or shape. Another very important feature is their ability to be formed, filled and sealed within an in-line process, which can be highly advantageous from an economic point of view. Optical properties (transparency, colour) can also be adapted to suit specific product requirements. have been developed in response to consumer demands for minimally processed foods of better quality and freshness, as well as to corporate sales changes with a clear increase in exports, centralized processing and greater distribution distances. Among the different active packaging strategies aiming to extend the shelf-life of food products, we find oxygen, moisture or ethylene scavenging systems, as well as strategies to release ethanol, flavours, functional ingredients or antimicrobial substances. 3. Coating or adsorbing antimicrobials onto polymer surfaces. 4. Immobilization of antimicrobials to polymers by ion or covalent linkages. 5. Use of polymers that are inherently antimicrobial. The most successful commercial application of active packaging has been sachets enclosed loose or attached to the interior of a package mostly containing moisture absorbers, oxygen scavengers or ethanol vapour generators [10]. But for antimicrobial packaging, this approach is only feasible with volatile compounds, which extremely limits the range of available antimicrobials. Volatile compounds may not be suitable for plastic processing due their poor heat resistance. Additionally, the incorporation of volatile compounds may release off-flavours within the packaged product. The direct application of antibacterial substances onto foods has limited benefits because the active substances are neutralized by product constituents on contact or diffuse rapidly from the surface into the food mass. As bacterial contamination occurs primarily on the surface, the incorporation of the biocide in a film or as a coating has many advantages due to the high exposure areas for the biocide and a reduction antimicrobial substances, like nisin, or incorporated in chitosan [15-18]. Chlorine and sulphur dioxide gases are also very effective in preventing mould growth. However, accumulation of these gases can lead to inacceptable colour alterations and toxicological problems in the treated food [19]. However, there is a growing trend to prevent artificial chemicals from being incorporated to food products or food contact materials. Therefore, many efforts are being done to replace artificial chemicals for natural substances, like enzymatic extracts, bacteriocins, essential oils, etc. potential for the development of new antimicrobial packaging concepts and there is extensive literature as to its antimicrobial efficiency, either alone or in blends with other polymers [28-30]. Another set of volatile antimicrobial compounds of great importance in research are natural essential oils (EOs), extracted from integrated plant material dental care, skin therapy, etc for more than half a century [32-33]. More recent...