On the trail of good fish quality

Pollution trends in fish, risks and possibilities of nanotechnology and a new decontamination process were the topics of a symposium organized by the German Research Society of the Fish Industry and the KIN Food Institute in Neumünster on 22 March 2011.

Despite the still high contamination of the waters with household and industrial chemicals, Dr. Horst Karl of the Max Rubner Institute (MRI) in Hamburg stated that there are only little effects on edible fish and that the residue values are often far below the maximum limits. For many organic residues such as Lindan or the sum of DDT compounds a clear reduction can be seen which is due to the global production and usage restrictions or bans. However, Dr. Karl also said that the dioxin load in wild eels from rivers flowing near large industrial zones, in fat fish from the Eastern Baltic Sea, and in codfish liver is posing a problem. In these cases the maximum values may be exceeded depending on the type of fish and the fishing grounds. According to current investigations of salmon and trout from aqua culture, a clear reduction in dioxins and dl-PCB was found as long-term trend.

Dr. Carsten Meyer, MRI, lectured on the current situation of nanotechnology. Today, this technology refers to the targeted production and application of nanoscale particles. Nanotechnology deals with network structures comprising of a few to some thousand atoms or molecules which are in general sized between 1 and 100 nanometers (1 nanometer equals 10^-9 = 0,000 000 001 meter). The chemical and food industries as well as medicine and environmental technologies all expect that the nanotechnology will provide superior benefits that will affect almost any area of life. According to Dr. Meyer, carbon-containing nanoparticles, metal and metalloid oxides, semi-conductors, metal sulfides and different polymers have been used in nanotechnology up to now. These particles have been mainly employed for surface treatment, for cosmetic products and textile finishing as well as for the targeted modification of food and material properties. Carsten Meyer said that the benefits and risks of nanotechnology are under discussion. Investigations showed that nanoparticles may intrude cells and affect cellular processes, possibly modify the genetic material or cause cell death. According to Dr. Meyer there are currently no sufficient analysis methods available for the handling and clarification of environmental and/or health hazard issues. Due to the lack of toxicological evaluation possibilities, there are no sufficient fundamental parameters available for legal regulations such as limiting values, work production rules and effect-related claims.

To improve this situation, the University of Applied Sciences, Flensburg, Germany, the Syddansk University, Odense/Sønderburg, Denmark, and the KIN Food Institute, Neumünster, Germany, have started a project on the "bioanalytical characterization of nanoparticles in food" in September 2010, added Dr. Bernhard Roth of the KIN. The objective of this project is the development of a biosensor test method for the detection of these extremely small particles (in the range of 10^-9 meter) which could be used in food, packagings or surface coatings. This project shall provide answers to the question on how to find out which nanoparticles in which size and concentration may pose a health hazard.

Another current field of applied research at the KIN Food Institute is the infrared treatment of food surfaces for decontamination purposes. According to Dr. Roth, a contamination of fresh salmon and smoked salmon with Listeria is always due to an external cross-contamination that occurrs during the processing. Listeria causes listeriosis, an infection that may have serious effects in pregnant women and adults with a weakened immune system. The KIN has considered the first research results obtained with smoked salmon as being partially excellent even though they are still not uniform. Head of the project Dr. Bernhard Roth thinks that there is a possibility to improve the microbiological load on smoked salmon, in particular Listeria monocytogenes, by surface decontamination or germ reduction methods via infrared treatment. However, further investigations in terms of germ reduction, color and texture of the salmon are necessary for the optimization of the process. Subsequently, the technologists at the KIN deal with the question whether such a system could be integrated into existing fish production plants and whether this method may be suitable for the treatment of other types of fish as well.