This report is intended to give a general view of the application of some analytical techniques to ensure seafood safety and authenticity, i.e. to prevent consumers from becoming ill and to make sure that product labels indicate actual content of the product.
Seafood has been implicated in 10-25 percent of food-borne disease outbreaks in developed countries (Nilsson and Gram, 2002; Valdimarsson, Cormier and Ababouch, 2003) due to its contamination with toxins, viruses, bacteria or parasites. Traditional methods to detect toxins are chemical analyses or the mouse test, which causes pain and death to the mice, and in addition is expensive and time consuming. There is, therefore, great interest in developing faster and user-friendly methods; immunological methods are among the best candidates for this purpose.
The discovery and characterization of pathogens and parasites has in the past depended on their size and how different they are from each other. For example, bacteria were not observed until the development of the microscope by Antony van Leeuwenhoek in the 1680s (Jay, 2000). The existence of viruses, suspected since 1892 by the Russian scientist Dimitry I. Ivanovski but not proven until the development of the electron microscope in the 1940s, permitted the visualization of individual viral particles (Britannica, 2000). Today it is suspected that the real impact of viruses on food-borne infections has been greatly underestimated because the classical techniques for detection of viruses are complicated and expensive and many viruses cannot be cultured. Development of molecular techniques may simplify detection and then their real influence on food safety can be mapped.
Parasites (trematodes or flukes, and nematodes) can cause serious seafood-borne diseases. Their study has been hampered because of their complicated life cycles, the fact that most of them do not cause immediate severe disease or quick death, and the difficulty of identifying the species and the life stage. They are also endemic in countries with poor sanitary conditions - usually poor countries where detection, treatment and eradication of these types of diseases come second to other parasitic diseases, particularly malaria. This has discouraged investment in the development of techniques for the specific detection and identification of these trematodes. The increase in international trade, travel and new fashionable food habits, such as sushi and sashimi consumption in richer countries, will undoubtedly contribute to the development of more reliable screening techniques and procedures for the elimination of these organisms from the food chain. In addition, due to the depletion of traditional fisheries (FAO, 2000a) and the need to cover the nutritional needs of increasing populations, more and more of the seafood consumed will come from aquaculture. It has been estimated that 85 percent of farmed fish is produced in developing countries, where parasitic infections are endemic in freshwater species.
It is now generally recognized that it is impossible to fully guarantee the safety of food, but it is possible to reduce the likelihood of accidents by implementing Hazard Analysis and Critical Control Points (HACCP) plans, together with good manufacturing (GMP) and good handling (GHP) practices, which include sound cleaning and disinfection procedures (see FAO, 1994,1999; NACMCF, 1992). Unfortunately, the use of some cleaning and disinfecting agents common in health care and in the food industry, has selected bacterial strains resistant to disinfectants and to some antibiotics (McDonnell and Russell, 1999; Paulsen, Brown and Skurray, 1998; Russell, 2000). Application of molecular techniques (in particular the polymerase chain reaction, PCR) and the increased accessibility of sequencing will aid in the detection and typing of unwanted bacteria and in characterizing some important properties, such as whether they are carriers of genes for resistance to antibiotics and/or disinfectants; thus, helping to reduce the impact of seafood-borne diseases in the population. Such techniques can also help to optimize processes, identify sources of contamination in natural reservoirs, processing environments and human carriers, then proceed to their elimination or treatment. In addition, they assist in selecting methods and chemicals for cleaning and disinfecting; thus avoiding the development of resistant strains and cross-resistance to antibiotics.
The second objective of this report is to describe methods to ensure the authenticity of seafood. This has become a problem mainly due to:
the great number of species used as human food (it is estimated that more than 20 000 species may be used worldwide for human consumption, about 500 in Europe alone [Rehbein, 2003]);
the increased consumption of fish products in which the morphological characteristics necessary for species identification have been removed;
increased international trade; and
the introduction of foreign species and increase of aquaculture due to overexploitation of traditional stocks (FAO, 2000a).
Consumers are entitled to truthful information about what they purchase; fishers and producers have the right to have their products known for what they are, and their quality recognized by the next link in the chain up to the final consumer; and finally, endangered stocks must be protected to allow them to recuperate to reach exploitable levels again. To fulfil those needs most countries have passed legislation to ensure correct traceability and product labelling (Anon., 2000; Commission of the European Communities, 2000). One section of this report is dedicated to the current legislation mainly in the United States of America and Europe, as these illustrate two different philosophies regarding the quantity and nature of information their citizens are entitled to have to make their choices (EC-DGA, 2003; The Fair Packaging and Labeling Act-USA).
The most suitable methods to ensure correct species identification are based on protein and DNA analyses. Consequently, databases containing species-specific protein and DNA profiles and sequences are being developed in many countries. However, in Europe these techniques are not sufficient to verify all the information that European products must or may carry: new techniques need to be developed for full authentication (freshness, method of production, geographic origin, processing parameters, etc). Isotope, trace element and magnetic resonance analyses seem to be the best candidates.
The European Council Regulation EU CR No 2065/2001 of 22 October 2001 makes it mandatory to indicate the geographical origin of capture of fish and whether it was cultivated or wild. Markers specific to breeding stocks can be used to determine the location of capture when there is also segregation between stocks. When there is not, one has to look to alternative techniques: trace element signatures and the distribution of natural isotopes seem to be among the most promising (Bilke and Mosandl, 2002; Martin and Martin, 1991; Secor et al., 2002). Wild and cultivated specimens of Atlantic salmon can also be distinguished by their lipid profiles (Aursand, Mabon and Martin, 2000).