PROJECT AMBASSADOR OF March 2015
Dr. Horst Karl / Max Rubner Institute-MRI, Germany
Dr. Horst Karl is involved in workpackage 6 (WP6), which deals with detection methods. This WP is particularly aimed at improving the visual, ultraviolet and molecular inspection methods for detection of parasites of human health significance in fishery products, making them usable by the industry, research bodies and sanitary authorities.
About Horst Karl
Dr. Horst Karl is a senior scientist at MRI and has over 20 years of experience in epidemiological studies on the occurrence and distribution of nematodes in various commercial important fish species. Based on his investigations minimum processing conditions to inactivate nematode larvae in fishery products were laid down in the former German fish regulation. He is the leader of the National Reference Laboratory for Anisakis, the German expert of the Commission’s Working Group on parasites in fishery products. He has been also chair of the West European Food Technologists’ Association (WEFTA) working group on analytical methods.
Which are the traditional methods used for detecting anisakids in fish? Are they sufficiently effective?
Several traditional methods exist to detect anisakids in fish. Generally, we have to differentiate between non-invasive and invasive methods. Non-invasive methods based on the visual inspection of whole fish and /or fillets as mandated by the EC. The intestines of whole fish can be inspected after opening the body cavity and anisakids can be removed by gutting of the fish. Fillets can be screened for parasites by candling. These methods are currently applied by industry on board of trawlers or at land based processing plants. Unfortunately, the visual inspection is relatively ineffective and cannot be applied to most processed products. The traditional invasive method is the artificial digestion of fish samples which has been applied by German control laboratories for more than 25 years. The flesh of fish is dissolved whereas anisakids remained intact and can be detected. However this technique bears several disadvantages: it is time-consuming, costly, needs laboratory equip-ment and specialized personnel.
Within the PARASITE project, new and improved methods are going to be developed. Can you tell us something about them? Which are their main advantages?
One task of the Parasite project aims to optimise and implement the UV-Press method as a simple, reliable, fast and quantitative detection of anisakids for routine inspection in fish and fishery products. The method utilises the fluorescence of deep frozen anisakid larvae and is based on visual inspection of pressed and subsequently deep frozen fillets under UV light. Prototype devices have been developed and tests are currently run by several project partners. One equipment is even set up on board of a Norwegian fish trawler. The technique allows a large-scale screening of samples in a comparatively short period of time. Other cutting-edge methodologies based on the detection of anisakid derived materials (such as specific nucleotide sequences, antigens and allergens) in fishery products are being developed within the Parasite project.
Are there different methods regarding the species to be detected or the type of product involved, i. e. fresh fish or processed fishery products (canned, surimi, etc)?
The UV-Press method can detect all anisakids in the edible part of all fresh or frozen fish species, as well as in the viscera and in some processed products like marinated or salted herring or anchovy fillets. If the nematode larvae are chopped during processing, e.g. in minced or heat treated (canned) products or surimi, we need other detection methods based molecular or immunological approaches.
The development and validation of such methods are under way, being an important part of the work package 6.
Once anisakids are detected in fish or fishery products, what should operators do? Are there alternatives to rejection?
There are alternatives to reject or to destroy valuable and sustainable caught marine fish resources. The results of the epidemiological study of WP2 will help the operators to get fish from less infected stocks or fishing locations. Anisakids are taken up by the feed of marine fish species and they are mainly located in the viscera and surrounding belly flaps. Parasites detected in the viscera can be removed by gutting of the fish and careful cleaning of the body cavity. For some fish species early gutting prevents the migration of nematode larvae from the viscera into the muscle meat. For other fish species the additional removal of the belly flaps can be a measure to reduce the risk of infection of the edible part.