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Cyclodextrin in active packaging of food Fenyvesi E.*, Balogh K.*, M.Sényi J.**, Siró I.**, Szente L.* Active, controlled and intelligent packaging of food and beverages has become a growing market nowadays. In a recent review the literature on the application of cyclodextrins (CDs) in active packaging has been summarized [1]. Now we report on a Hungarian project which aimed to develop films with added functionalities, such as antimicrobial, antioxidant and odor absorbing effect, for food packaging. CD-containing polyethylene (PE) and poly(vinyl chloride) (PVC) films were developed by two universities (Eötvös University and Budapest Corvinus University), two small or medium sized enterprises (SMEs) (CycloLab and PlastLine) together with an industrial partner (BC Ongropack) in the frame of a national project in Hungary. The 2-year research has succeeded in its objectives as follows: The permeability studies showed that the films without CD were impermeable for the flavors studied, while the compounds (vanillin, carvone) able to form complexes with βCD can penetrate through the films containing "empty" βCD [1]. The mechanism of these processes (diffusion to the membrane in the donor phase, complex formation, dissociation within the film, release in the acceptor phase) is illustrated in Fig. 2. The films always included the active substances more evenly The release of the active ingredient from the films was usually slower when it was complexed [2]. An example is shown in Fig. 3 clearly indicating that the low menthol content is released fast from the films containing menthol/cellulose mixture, while a sustained release was observed from the films with menthol/βCD complex having higher menthol content due to the stabilizing effect of the CD. Films containing the complexes of antimicrobial The films modified by "empty" CD were tested as odor absorbing packaging material for garlic. The applied βCD concentration (1 and 2%), however, was not enough to find any difference neither by perception nor by gas chromatographic investigation compared to the control films. The films containing antioxidants were used for poppy seed storing experiments with the same result: the film did not contain enough complex (appr. 2% complexes were used), to show any difference in prevention of rancidity compared to foils including only vitamin E.
As a conclusion the enhancement of the CD-content is a fundamental task. The know-how of achieving the nearly 3% complex-content without significant reduction in the film’s mechanical qualities has been worked out in case of PVC films. Similar solution is planned in case of PE. In fact the objectives of the project has been complied successfully: The prior objective of the project was the enhancement of the food safety, improvement of the shelf life due to active packaging materials. Films at least partly biodegradable were developed. Although these films contain the microbicide or static, antioxidant or other active substances in a formulation, which release the active ingredient only under proper circumstances (humidity, temperature), at the necessary speed and quantity, realizing the antifungal and/or antibacterial inhibiting or preservative effects only on the surface of the packaged product to be protected preventing in this way the harmful active ingredients from getting into the food and also into the human organism. The controlled release of the active substance was implemented by inclusion complex formation. The problems of compatibility between hydrophilic CD and hydrophobic packaging material (PE and PVC) were more or less solved. In case of PVC using less hydrophilic inclusion complexes turned out to be enough while in case of PE use of lubricant and application of master blends were needed as well. The experience gained as a result of the manufacturing has been put down in a know-how. In the case of PE further technological optimization is necessary for the final description. Thanks are due to the National Competitiveness Programme of Hungary (GVOP-3.0-0217-04) for financial support and to late Prof. Jozsef Szejtli for initiating the research and development within the project. References
1. CD News editorial |
life of food products were complexed by α – or βCD and incorporated into PE and PVC films (Fig. 1). The complexation of the selected antimicrobial, antioxidant, or other e.g. ripening agents and fragrances was confirmed by thermoanalytical methods. The compounds having antimicrobial effect (imazalyl, allyl isothiocyanate) remained effective even in the complex form as it was proved by microbiological tests using various bacteria and fungi. Having solved the numerous problems in the production technology, films characterized by microscopy, mechanical and permeability studies were produced using the complexes and "empty" CD.
compared to films containing the substance in uncomplexed form by itself or in a mixture with cellulose. Volatile actives, like menthol or allyl isothiocyanate were evaporated at 170-180 oC during the manufacture of the films unless they were protected by complexation.
compounds showed antimicrobial effect, the films containing antioxidant α-tocopherol / βCD complex had antioxidant effect.
Undeniable difference was observed in case of PVC foils containing imazalyl/BCD complexes with antimicrobial effect: by increasing the complex concentration the putrefaction of the packaged bananas was reduced. Fig. 4 shows the bananas stored for 12 days at 13 ºC. The PVC film containing nearly 3% complexes turned out to be a real active packaging material, which can preserve the quality of the packaged food.
