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materials from the food production are focused on here because no extra production process is required. The quantity of foods produced is hence not diminished and the carbon footprint is improved. Nevertheless, the barrier properties of biobased packaging materials remain a challenge. Their water vapor permeability is generally high and only in a few cases does the oxygen permeability match that of crude oil based polymers. The expertise and knowledge-based technologies of the Fraunhofer IVV are sought after here for the development of improved systems to meet food packaging requirements.
Packaging systems with customized permeation properties
The most important function of packaging is to protect products from, for example, contamination, microorganisms, and mechanical damage. Oxygen and water vapor permeation are, however, the most detrimental factors for product shelf-life.
For foods, packaging with “suitable” barriers must be selected. Oversized impermeable packaging can have adverse consequences if, for example, fresh salad produce or vegetables are no longer able to breathe oxygen and metabolize. Such over-packaged products can also be very expensive. Neither packing companies nor consumers want this over-packaging. In order to customize packaging for a specific food product, it is vital to have knowledge about the maximum permissible exposure to oxygen and water vapor. Other factors are the desired shelf- life and storage temperature (storage on open shelves or refrigerated shelves). Known algorithms allow permeability values for oxygen and water vapor to be calculated. At the Fraunhofer Institute for Process Engineering and Packaging IVV a data table can be used to select a suitable packaging material, based on the material thickness and whether a seal is necessary. Printing, size, and sterilization are other factors that have to be into account here.
Very sensitive food products sometimes require modified atmosphere packaging (MAP). Here the permeability of the packaging material to the MAP gas plays a key role. If the permeation in and out is not matched, then shrunken packaging can result. This occurs when gases inside the packaging permeate out faster than gases permeate in from the ambient air. Swollen packaging can also arise, with consumers often incorrectly believing this is due to microbial spoiling. If customized, as with packaging for crisps, the gas can also provide mechanical protection for the product. So-called active barriers in the packaging material are another promising approach. For example, oxygen- scavengers can be incorporated into a film or coating. These remove the oxygen from the packaging headspace and protect the contents until the oxygen absorption capacity of the scavenger has been exhausted. Such scavengers also exist for ethylene (produced in ripening processes) and for water vapor. A special case here is purposeful creation of an ideal relative humidity in a packaging, namely below the limit for microbial growth yet above the level at which the food dries out.
Packaging systems made from renewable raw materials should come from sources that do not compete with food production. Residual
In general, the highest barrier requirements are required for technical films. Photovoltaic cells, whether they be thin film photovoltaic cells or organic photovoltaic cells, must be encapsulated in an effective water vapor barrier otherwise the cells would lose their functionality after a short time. This involves multilayer systems comprising inorganic layers applied by vapor deposition and organic or hybrid polymer coatings. Depending on the requirements, one or two pairs of layers are used. Other technical products that require barriers against oxygen and water vapor are electrochromic displays, thin film batteries, vacuum insulation panels, thin film transistors, and OLEDs, with the latter having the highest barrier requirements.
The Fraunhofer IVV is actively involved in all these areas and is an expert partner for innovative development work, characterizations, and evaluations. A broad range of R&D work can be carried out using the specialist analytical equipment and pilot plant facilities.
Author: Dr. Klaus Noller, Fraunhofer Institute for Process Engineering and Packaging IVV
10 - 12 March 2015 • Munich Trade Fair Centre, Germany
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Branchen-News | Industry News ICE
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