Service Communautaire d'Information sur la Recherche et le Développement - CORDIS

Final Activity Report Summary - MICRO-GMAP (Multipurpose Tuneable Microwave Plasma Source of Germicidal Modified Atmospheric Packaging for Food Industries)

Food and drink is the major industrial sector in the EU, dominated by SMEs and threatened by erosion of world markets and slowing growth. Continued wealth creation requires innovation built on a strong scientific and engineering base for training, new knowledge and innovation to support the sector. Collaboration and knowledge transfer between engineering and microbiology are required for rapid progress. The two year, interdisciplinary MICRO-GMAP at Liverpool John Moores University (LJMU) has created new competencies on the interface of engineering and microbiology. The MICRO-GMAP project involved in the development and testing of a novel microwave plasma UV and ozone source operating at various frequencies from 2.45 to 18 GHz and its application to new food packaging and water/wastewater technologies.

The microwave plasma UV/O3 source differs significantly from conventional UV lamps. It has no warm up time; it is tuneable in wavelength and can operate in continuous and pulse mode with intensity higher than the conventional system. Each year the food distribution chain has an increased demand for fresh products with longer shelf lives, and therefore supermarkets and food producers are constantly looking for improved production methods. Treatments with ultraviolet energy and ozone offer several advantages to available washing and sanitising methods as they do not leave residues and do not have legal restrictions or require extensive safety equipment.

The germicidal properties of UV irradiation are situated in the UV-C region of the spectrum (200-280nm), and more specifically around 254 nm. This wavelength is absorbed by the nucleic acids (DNA and RNA) of microorganisms and prevents them from multiplying. Reducing the number of bacteria and other microorganisms is especially significant in the case of minimally processed products, where UV together with refrigeration and several modifications in packaging, including modified atmospheres, can play a very important role in increasing lifespan and decreasing the risk of food poisoning. However, one of the drawbacks of UV is that it does not work in shadowed areas. However, one of the advantages of the LJMU lamp is that the shape and size can be adapted to suit the product being irradiated with various percentages of UV/Ozone.

Some products such as sliced meat present a flat surface, which lends itself readily to UV treatment. Other products such as bread have a porous crumb structure that is less easily sterilised by UV light but could be treated with ozone. Combining UV and O3 could provide sufficient sterilisation which when combined with Modified Atmospheric Packaging (MAP) results in safer product and/or extended shelf life. Traditionally the detection of viable microbes (bacteria, fungi) used culture methods using selective media. Colony counts were used to enumerate environmental populations.

These are still standard techniques and provide valuable information. However, there are now a wide variety of rapid methods based on strategies such as ATP fluorescence to non-specifically detecting viable organisms and immunological identification (ELISA) to identify them. Attention is focussed particularly on molecular biological methods, including non-culture methods (e.g. PCR and 16S rDNA sequencing) which allow the detection and identification of 'viable-but-not-culturable' organisms. Other DNA methods DGGE and FISH) allow the change in diversity of microbial populations to be assessed.

Understanding the persistence of bacteria within the environment and in particular the response of mixed populations to biocidal stress is a challenge to microbiological research. A combination of engineering and microbiological innovation at Liverpool John Moores University has advanced the technology of UV light production and its application in food and waste-water microbiology. A pilot model of the microwave plasma UV/O3 has been developed which generates both UV and O3. This is novel technology. Compared with conventional lamps, it was more efficient and had a longer lifetime and lower UV production cost per Watt of electrical power.

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United Kingdom
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