The 31st annual meeting of the WEFTA Working Group on Analytical Methods took place under the chairmanship of J. Oehlenschläger / H. Karl, Germany, at the MAX RUBNER - INSTITUTE, Federal Research Institute of Nutrition and Food, Institute of Safety and Quality of Milk and Fish products, Palmaille 9, in 22767 Hamburg on Thursday / Friday June 11-12, 2009.
The meeting of the “Working Group on Analytical Methods” was attended by representatives from 7 institutions of the following countries: Belgium, Denmark, Germany, Iceland, Italy, Spain and Turkey.
- Reorganisation of the work of the analytical working group, publication of WEFTA and home methods on WEFTA homepage
- Importance of tropical species in each country
- Collaborative trial on canned sardines (France)
- Parasites progress report
- Results of inter-laboratory trial on fat determination (Germany)
- Actual laboratory questions, problems and “good to know” issues
- Date and place of the next meeting
Publication of WEFTA Analytical Working Group activities on WEFTA homepage
The methods have still to be placed on the home page: Method Salt determination, TVB-N, nitrogen (protein), pH-value, fat, species identification , indol, sulfite
Importance of tropical species in each country
The questionnaire was cancelled, as no reliable data on the importance of tropical species were available in the different countries.
New additives (water-binding substances; e.g. citric acid and Na-carbonate) are applied for Pangasius (mainly problems with frozen fillets from China or SE-Asia) which are more difficult to detect. The ratio Na/K (naturally 10:100 in marine fish) will be an indicator. Determination via atomic absorption spectrometry (AAS) or via stable isotopes is possible.
Adding of water can also a problem with shrimps.
The nitrogen factor was used in former times (in relation to water content).
Collaborative trial on canned sardines (France)
Ifremer is interested to organize a collaborative trial with different sardine species. Possible participant are Germany, Ifremer, Portugal, Belgium, Spain (Vigo) and Maroc. One problem is to obtain six different authentic species of at least 10 kg each.
Some heavily infested fish (species) have been found during the research cruise of German research vessel Walther Herwig III in a cooperative work of Spain and Germany. Infestation seems to increase. Problem: what do fishermen do with the gut? In practise it is thrown out although this is forbidden in some countries. Problems are also sushi (only frozen for 24 h – not reaching -20C in the center) and marinated anchovies (if fish not frozen before). From Dec 2006 it is compulsory in Spain to freeze at 20ºC for 24 h in the thermal center for institutions (restaurants, cafeterias, hotels, hospitals, schools, catering companies etc) serving food to final consumers.
Important is the standardisation of the analytical procedures. During frozen storage the surface of some individuals of Anisakis may be damaged. The Codex method is based on pepsin (digestion). If the cuticle is damaged the resistance to pepsin decreases and the larva may be destroyed so that the analysis may not find all. In Norway they use image analysis (non-destructive) for cod. The group has discussed a ring test or practical experiment at the next meeting.
Results of inter-laboratory trial on fat determination
The results of the second inter-laboratory trial (according to international standards) on fat determination applying a modified method according to Smedes were presented. Participants: Germany (second lab), Italy (2x), Belgium, France, Turkey, Spain and Denmark.
Samples were raw mackerel (blind duplicate), matjes, smoked salmon and raw cod.
The z-score for proficiency tests proved that this method can be used as standard method. Most labs will continue to use the method. The method worked also fine for eel samples (fat content 35%).
Actual laboratory questions, problems and “good to know” issues
H. Karl gave information on protein determination applying Dumas technique (Leco instrument; approx. 23.000 Euro). Fish flesh, meal and sauce were compared with traditional Kjeldahl. Advantages are no solvents and no waste. For milk the results differ too much and the method has to be adopted. H. Palmadottir is getting higher values for protein in fish meal. M. Timm-Heinrich informed about “Sprint” instrument for protein determination – will be able to test the instrument after summer holiday. Problem: some fish species have a high content of NPN (non-protein-nitrogen = nucleotides).
Date and place of the next meeting
The 32nd meeting will be held in Lisbon, Portugal, 3rd June 2010.