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B1-IL: DEVELOPMENT AND VALIDATION OF A RAPID SPECTROSCOPIC METHOD TO DETECT THE FRAUDULENT TREATMENT OF TUNA FISH WITH CARBON MONOXIDE
Enrica Droghetti (1), Claudia Focardi (2), Gian Luca Bartolucci (3), Massimo Bambagiotti Alberti (3), Mila Nocentini (2), Giulietta Smulevich (1)
1 Dipartimento di Chimica “Ugo Shiff”, Università di Firenze,
Via della Lastruccia 3, I-50019 Sesto Fiorentino (FI), Italy
2 Istituto Zooprofilattico Sperimentale delle Regioni Lazio e Toscana,
Sezione di Firenze,
Via di Castelpulci 41, I-50010 San Martino alla Palma (FI), Italy
3 Dipartimento di Scienze Farmaceutiche, Università di Firenze,
Via Ugo Schiff 6,I-50019 Sesto Fiorentino (FI), Italy
Carbon monoxide (CO) is commonly employed in the United States and in the Netherlands to treat fish products at industrial level [1]. CO forms with ferrous myoglobin (Mb) of fish tissues a very stable complex, MbCO, which impairs for a long period a cherry-like colour to these products. This treatment can mislead the consumers, who often evaluate the freshness of fish fillets exclusively by their colour, that in the fresh product is impaired by the bright red complex MbO2 (oxy-Mb) and is subjet to changes upon aging due to the oxidation of oxy-Mb (Fe2+) to brown met-Mb (Fe3+). The treatment with CO, which partially prevents this oxidation process, avoids the change of colour of fish tissues, thus hiding to the consumer the degradation process of tuna fish. This treatment may mask spoilage, because the CO-complex can be stable beyond the microbiological shelf life of the meat.Although CO-treated food consumption does not represent a risk for the consumer, it is very important to assess the toxicological risk associated to the prolonged shelf-life of these products. As far as aquatic food is concerned, in particular for histidine-rich fishes such as tuna, mackerel, sardine, herring, swordfish, the use of CO provides an additional risk since histamine, responsible of toxicological effect, can be formed as a consequence of decomposition of histidine.
Recently, a confirmative method for quantitative determination of CO in commercially treated tuna and mahi-mahi tissues using gas chromatography/mass spectrometry (HS-GC/MS) has been proposed to detect CO in the tissue of tuna fish [2]. This method reaches low detection and quantitation limits, however the official laboratories of food control need not only confirmatory methods, but also rapid low cost screening methods for everyday activity. Thus we have developed a simple and rapid spectrophotometric method to detect qualitatively the presence of MbCO in CO-treated tuna fish [3]. This procedure is based on the combined analysis of electronic absorption spectra (UV-Vis) in their normal and second derivative modes. The different forms of Mb can be distinguished by their peak positions and relative intensities, since the wavelength maxima vary according to the oxidation, spin, and coordination states of the heme iron. This method is presently used as a screening method in the laboratory of food control of the Italian Istituto Zooprofilattico Sperimentale delle Regioni Lazio e Toscana.
In the present work a method that allows the quantitative determination of CO in the meat drip of tuna fish by UV-Vis spectroscopy is proposed. It consists of: i) preparations of CO standard solutions titrated against horse heart Mb primary standard solutions; ii) determination of calibration curves to measure CO concentration in treated and untreated samples. The calibration curves will be presented together with the results obtained on different treated and untreated samples of meat drip of tuna fish.
Moreover, the quantitative UV-Vis results will be compared with those obtained via a HS-GC/MS method. CO level measured by UV-vis in tuna fish samples is substantially lower than that revealed by HS-GC-MS. The origin of this discrepancy will be discussed.
References
- L. Martínez, D. Djenane, I. Cilla, J.A. Beltrán, P. Roncalés, Meat Sci., 2005, 71, 563-570.
- C.R. Anderson, W.H. Wu, J. Agr. Food. Chem., 2005, 53, 7019-7023.
- G. Smulevich, E. Droghetti, C. Focardi, M. Coletta, C. Ciaccio, M. Nocentini, Food Chem., 2007, 101(3), 1071-1077.
Prof. Giulietta Smulevich is a professor at the Chemistry Department, University of Florence, Italy. Prof. Smulevich has been teaching: Physical Chemistry, Environmental Physical Chemistry, Biophysical Chemistry, Applications of Optical Spectroscopies to Biological Molecules and Physical Chemistry of Biological Macromolecules. Her research interests include: structure–function relationships in heme proteins via vibrational (IR and resonance Raman) and electronic absorption spectroscopies; Raman and SERRS (Surface Enhanced Resonance Raman Scattering) of biological molecules with application to the detection of residuals of drugs in food; development and validation of optical spectroscopic methods to detect carbon monoxide in fish and meat products; intramolecular excited state proton transfer of model compounds via fluorescence excitation and emission; transform analysis and resonance Raman spectra of model compounds, anthracyclines and their DNA complexes.
