A rapid spectroscopic method to detect the fraudulent treatment of tuna fish with carbon monoxide |
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Authors: | Giulietta Smulevich Enrica Droghetti Claudia Focardi Massimo Coletta Chiara Ciaccio Mila Nocentini |
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Affiliation: | 1. Dipartimento di Chimica, Università di Firenze, Via della Lastruccia 3, I-50019 Sesto Fiorentino (FI), Italy;2. Istituto Zooprofilattico Sperimentale delle Regioni Lazio e Toscana, Via di Castelpulci, 41, I-50010 San Martino alla Palma (FI), Italy;3. Dipartimento di Medicina Sperimentale e Scienze Biochimiche, Università di Roma Tor Vergata, Via Montpellier 1, I-00133 Roma, Italy |
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Abstract: | Carbon monoxide (CO) can be used to treat fresh meat and fish in order to retain its ‘fresh’ red colour appearance for a longer period of time. In fact, upon aging, myoglobin is oxidized to met-myoglobin with the concomitant blue-shift and broadening of the Soret maximum, which brings about a change in the colour of the fish, revealing that it is no longer fresh. The use of carbon monoxide, which reacts with the oxy-myoglobin to form a fairly stable cherry red carboxy-myoglobin complex may mask spoilage, because the CO-complex can be stable beyond the microbiological shelf life of the meat. The presence of CO in tuna fish has been investigated by optical spectroscopy as the formation of the CO adduct can be easily detected by the combined analysis of electronic absorption spectra in their normal and second derivative modes, monitoring the intense Soret band at 420 nm. The presence of met- and oxy-myoglobin can obscure the presence of small amounts of the CO adduct; however, it can be revealed by chemically reducing the met- and oxy-forms to the deoxy-form in an anaerobic environment. This spectroscopic method provides a qualitatively rapid laboratory screening procedure for food control to unmask the presence of CO in frozen or fresh fish. |
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Keywords: | Myoglobin-CO complex Electronic absorption Second derivative Tuna fish |
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