Effect of marination and smoking on lipid and fatty acid composition of thornback ray (Raja clavata) and spiny dogfish (Squalis acanthias)

The effects of different processing methods (marinated and smoked) on proximate compositions and fatty acids of thornback ray (Raja clavata) and spiny dogfish (Squalis acanthias) were investigated. Total lipid content was 3.39% in thornback ray and 5.90% in spiny dogfish. The lipids of raw fish consisted mainly of polyunsaturated fatty acids in thornback ray and saturated fatty acid in spiny dogfish. The n?3/n?6 ratio of thornback ray (3.78) was higher compared to spiny dogfish (2.87). After processing, water content decreased significantly while crude protein, lipid, and ash contents increased in both fishes. In general, processing techniques significantly (p?<?0.05) affected fatty acid fractions; in both species, SFA content increased, MUFA and PUFA content decreased. In addition, after processing n?3/n?6 ratios increased although total n?3 and n?6 contents decreased. The results indicated that heat treatment and acidic medium during processing had considerable affects on the proximate and fatty acid composition of the final products. Marinated and smoked products prepared from both fish species offer a balanced fatty acid composition for human nutrition. In terms of fresh and processed products, while the spiny dogfish appears to have a higher PUFA content, the thornback ray is a richer source of EPA?+?DHA.     

Fast determination of arsenic,selenium, nickel and vanadium in fish and shellfish by electrothermal atomic absorption spectrometry following ultrasound-assisted extraction

Ultrasound-assisted extraction of As, Se, Ni and V from fish and shellfish has been applied as a fast and reliable sample pre-treatment method for accurate determination of the four elements by electrothermal atomic absorption spectrometry with Zeeman (As, Se) or Deuterium (Ni, V) background correction. A multivariate optimization approach has been employed for establishing the effect of variables influencing the extraction process. Under suitable conditions, quantitative extractions occurred from a 10 mass sample (particle size <100 μm) suspended in 1.5 mL of acidic extractant (0.5 or 3% v/v HNO₃) and subjected to high intensity ultrasound (50% amplitude; 3 min). The method was successfully validated against the following certified reference materials: NRCC-DORM-2 dogfish muscle, NRCC-DOLT-2 dogfish liver, NRCC-TORT-2 lobster hepatopancreas, NIST-SRM 1566b oyster tissue and BCR 627 tuna fish. The following seafood samples were analyzed: hake (Merluccius merluccius), sole (Solea solea), clam (Venerupis rhomboides), prawn (Panaeus kerathurus), cuttlefish (Sepia officinalis), shrimp (Palaemon elegans), razor shell (Ensis ensis), cockle (Cardium edule), Mussel (Mytilus galloprovincialis), edible crab (Cancer pagurus), meagrin (Lepidorhombus whiffiagonis). The concentration ranges (μg/g, dry weight) for the elements determined were as follows: As (12.6–190), Se (0.73–2.34), Ni (2.94–46) and V (0.82–5.14). The detection limits (LODs), defined as 3s/m (s being the standard deviation of 10 blank and m the slope of the calibration graph), in dry tissue were 0.6, 0.3, 0.2 and 0.4 μg/g for As, Se, Ni and V, respectively. Between-batch precision was expressed as relative standard deviation from three separate extractions was in the range 3–10%.     

C NMR as a tool for authentication of different gadoid fish species with emphasis on phospholipid profiles

The aim of this study was to evaluate if phospholipid profiles obtained by ¹³C nuclear magnetic resonance (NMR) spectroscopy is characteristic enough to separate species of lean gadoid fish. ¹³C NMR data were obtained from muscle lipids of five categories of lean gadoid fish, namely, north-east arctic cod and Norwegian coastal cod (Gadus morhua), haddock (Melanogrammus aeglifinus), saithe (Pollachius virens), and pollack (P. pollachius). A total of 27 fish caught at the same location on the Norwegian coast in the traditional fishing season (March/April) in 2006 were analysed. The sn-2 position specificity of 22:6n-3 (docosahexaenoic acid, DHA) in phosphatidyl choline (PC) and phosphatidyl ethanolamine (PE) for the different species/stocks were investigated, and the full ¹³C NMR spectra applied in multivariate analysis. Stereospecific distribution calculations showed significant differences among species in the distribution of 22:6n-3 in PC and PE, and the pollack group displayed the lowest values for 22:6n-3 in sn-2 position, both in PC and PE. This first screening showed that by using the ¹³C NMR fingerprint of muscle lipids, linear discriminant analysis gave a correct classification rate of 78% according to the five categories of lean gadoid fish, while successful classification (100%) was achieved with Bayesian belief networks (BBN) predictions.     

Molecular identification of Anisakis type I larvae isolated from hairtail fish off the coasts of Taiwan and Japan

Anisakid nematodes are known to cause the zoonotic disease, anisakiasis, through the consumption of raw or undercooked fish. The parasites most frequently associated with the disease in humans are categorized as Anisakis type I, which comprise several species of the genus Anisakis. The larvae show primitive forms and lack the detailed morphological characteristics required for precise species identification. Thus, molecular characterization is necessary for determining the species of Anisakis type I larvae and acquiring important clinical and epidemiological information. In this study, we isolated Anisakis type I larvae from hairtail fish caught off the coasts of Taiwan and Japan. The ribosomal DNA (rDNA) internal transcribed spacer (ITS) region was sequenced, and restriction fragment length polymorphism (RFLP) analyses using HinfI and HhaI was carried out for species identification. Most larvae isolated from hairtail caught in Taiwan were Anisakis typica (84%), while those isolated from hairtail caught in Japan were almost exclusively identified either as Anisakis simplex sensu stricto (65%) or Anisakis pegreffii (33%). This is the first report of A. typica in fish obtained from Taiwan. Our results shed the light on the epidemiology of Anisakis type I larvae, which is a potential cause of human anisakiasis in Taiwan and Japan.     

Alteration of the electrophoretic pattern of myofibrillar proteins in fish mince during frozen storage

A study was made of the variations in the electrophoretic profile of myofibrillar proteins in the muscles of blue whiting (Micromesistius poutassou R.), horse mackerel (Trachurus trachurus L.) and mackerel (Scomber scombrus L.). It was shown that all species presented different deterioration patterns during frozen storage. The fish were caught at two separate times of the year (winter and summer) and were stored frozen at -18°C for 1 year. The results indicate that during frozen storage, electrophoretic patterns varied according to species. Comparison of myosin heavy chain/actin (MHC/A) ratios indicates that blue whiting is the species that undergoes most alteration, and that this is more intense in fish caught in the summer than in the winter. Alteration of the MHC/A ratio was similar in horse mackerel and mackerel caught in the winter, whereas in the summer horse mackerel proved to be the most stable species. In all cases, the reduction of the MHC/A ratio was due essentially to alteration of the MHC, an effect which was particularly marked in blue whiting. Tropomyosin remained stable throughout the storage period in all three species.     

The assessment of organic mercury in Baltic fish by use of an in vitro digestion model

The organic mercury content of five commercially valuable fish species (cod, flounder, turbot, perch and herring) was determined by use of an invitro digestion model in order to assess health risk of fish caught within the Polish Exclusive Economic Zone of the Baltic Sea. Concentrations of total mercury and organic mercury were measured in the muscle tissue of fish and in the products of two-stage gastrointestinal digestion, using atomic absorption spectroscopy (AMA 254). The highest concentrations of organic mercury were found in the muscles of predatory fish that dwell in near-bottom waters. Based on a bioaccessibility estimate obtained from the in vitro digestion model, it was found that only 26-62% of organic mercury, depending on the species of fish, was released into the intestinal lumen during the digestion of muscle. Therefore, to postulate the potential toxicity of fish, based on the organic mercury content of the muscle tissue ingested by consumers, is unfounded. The risk assessment should be carried out on the basis of another parameter - the bioaccessibility of organic mercury.     

Contaminant metals in black scabbard fish (Aphanopus carbo) caught off Madeira and the Azores

Total mercury, cadmium and lead concentrations were measured in black scabbard fish (Aphanopus carbo), caught off Madeira and the Azores archipelagos (Portugal). The metal contents were expressed in mg kg⁻¹ wet weight. The mean mercury levels in liver were 4.50 and 2.37 whereas, in skin, such values were 0.59 and 0.36 (Madeira and Azores, respectively). On average, the muscle content was around 0.9 in fish from both areas. Cadmium maximum levels in muscle and skin were found in Azores samples (0.09 and 0.11, respectively). Mean lead contents in all samples were always below than 0.10. In general, the results obtained did not allow the establishment of any relationship between metal accumulation and fish weight or length. According to the permissible WHO and FAO levels, these results, suggest that this species does not represent a risk for human consumption if the liver is excluded and the edible part consumed with moderation.     

Determination of metals in fish and mussel species by inductively coupled plasma-atomic emission spectrometry

The concentrations of cadmium, iron, lead, zinc, copper, manganese, nickel, chromium and cobalt were determined by ICP-AES in muscles, livers, gills and skins of two fish (Clarias gariepinus and Carasobarbus luteus), and in muscles and gills of two mussel species (Unio terminalis and Potamida littoralis) sampled from the Lake Gölba??. Iron showed the highest levels in all examined tissues of both fish species. Following Fe; Zn showed the second highest levels in all examined tissues of both fish species except Mn levels in muscle and gill of C. luteus. In both mussel species, to the contrary fish, manganese showed the highest levels in examined tissues, and followed by Fe. In both fish species, the all metal concentrations in livers were higher than those in muscles. Concentrations in tissues of the analyzed metals were significantly affected by species. There were differences between the metal levels in the similar tissues of the different species (p < 0.05). At the same time, there was also the differences between the metal concentrations in different tissues of the same species (p < 0.05). Metal levels in tissues were compared with national and international permissible limits. Metal concentrations in both edible and other tissues of the sampled species were within the permissible safety levels for human uses.     

Biogenic and volatile amine-related qualities of three popular fish species sold at Kuwait fish markets

Three fish species commonly consumed in Kuwait were studied for their total volatile base nitrogen (TVBN) and biogenic amine composition during normal commercial activities at the fish markets. Samples of the fish species Zubaidi or silver pomfret (Pampus argenteus), Hammour or orange–spotted grouper (Epinephelus coioides), and Negrule or grunt (Pomadasys kaakan) were analyzed using steam distillation and high performance liquid chromatography (HPLC) procedures. Fish samples collected in the morning had lower levels of TVBN, ranging from 25.9 mg/100 g to 30.2 mg/100 g compared with the range of 31.2 mg/100 g to 40.9 mg/100 g for samples collected in the evening. Among all three fish species, Zubaidi (Pampus argenteus) showed the lowest TVBN content while Negrule (Pomadasys kaakan) had the highest. Biogenic amine levels were also low in the fish species. The data suggest that fish handling practices at the fish markets in Kuwait do not result in significant abuse of fish temperatures, and that the amounts of volatile and biogenic amines produced during normal activities did not rise to levels indicating fish decomposition.     

Accumulation of arsenic in different fresh water fish species – potential contribution to high arsenic intakes

The aim of the study was to evaluate total arsenic (As) in five tissues (gills, mouthpiece, intestine, liver and muscles) of 10 fish species caught from As contaminated Manchar Lake (26°3′N: 67°6′E) Sindh Pakistan during 2006–2007. The total As concentration was determined by hydride generation atomic absorption spectrometry (HG-AAS), prior to microwave assisted acid digestion. The certified reference material DORM-2 (dogfish muscle) was used to check the quality control of the technique. The good agreement with the certified value at 95% confidence limit confirmed the validity of As determination method. The limit of detection (LOD) and limit of quantitation (LOQ) of As were 0.034 and 0.11 μg/g, respectively.     

Effects of catching methods on quality changes during storage of cod (Gadus morhua)

The catching method, storage time and composition of fish are factors that influence the quality of fish. Different opinions have been expressed concerning the effect of catching methods on the fish quality. In this work cod caught at the same time and location, using different catching methods (gillnet and longline) has been stored for up to 16 days. The same soaking time was used for both fishing gears. No differences due to fishing gear was observed in the quality attributes QIM score, water content, TVN, DMA, TMA, TMAO, Freshmeter-readings, total viable count, sulphide producing bacteria and P. phosphoreum during storage. The catching method had significant influence on pH only. It is shown that the pH of the fish caught by gillnet is lower than pH of fish caught by longline. It is also shown that fish caught by gillnet have higher K-factor than fish caught by longline. The pH of the fish muscle is closely correlated to K-factor; higher K-factor supports lower pH.It is also shown that by using the quality parameters water content, TVN, DMA, QIM score, Freshmeter-readings, TVC, sulphide producing bacteria, and P. phosphoreum, the storage time in ice can be predicted with a correlation of 0.99 and a prediction error of 0.8 day.     

Quality assessment of laminated fillet blocks from blue whiting (Micromesistius poutassou)

Laminated fillet blocks made from blue whiting (Micromesistius poutassou) caught in February and April were assessed for quality. The total protein nitrogen value in February-caught fish was greater than the April-caught fish. The bone content, water content and pH values were consistently lower in the February fish than the April fish. Measurement of the acceptability of deep fried, breaded fingers made from the fish and compared with cod fingers produced from fish caught at the same time of year showed a consistent difference between the cod and blue whiting. In addition, the fish fingers from fish caught in February scored consistently higher than those caught in April. The implications of the findings are discussed.     

Heavy metal contaminants and processing effects on the composition,storage stability and fatty acid profiles of five common commercially available fish species in Oron Local Government,Nigeria

Five commercially available common fish species: catfish (Chsysichthyes nigrodigitatus), tilapia (Oreochromis nilotichus), ilisha (Ilisha africana), bonga (Ethmalosa fimbriata) and mudskipper (Periophthalmus koelreuteri) in Oron Local Government Area were evaluated for their content of heavy metals and the effects of salting on nutrient contents, oxidative stability and fatty acid profiles of smoke-dried fish cakes. Concentrations of heavy metals in edible muscle, liver and gill tissues were determined while the oxidative rancidities in unsalted and salted smoke-dried fish cakes, packed in low-density polyethylene (LDPE) bags and stored at 30 ± 1 °C were assessed using peroxide value (POV), thiobarbituric acid (TBA) value, free fatty acid (FFA) contents and sensory evaluation techniques. Generally the analytical data for Cu, Zn and Pb in the muscle, gills and liver of test samples were significantly low. Similarly, insignificant concentrations (<0.001 mg/100 g) of Hg, As, Cr and Cd were obtained in the fish tissues. The protein and lipid contents of the fish cakes ranged from 60.8–63.9% to 7.3–9.1%, respectively. Salting caused minimal reductions in the nutrient contents of the dried fish cakes. The POV, TBA, FFA and taste panel scores were highest during the first week of storage and declined thereafter. Salted smoke-dried samples had higher POV, TBA and FFA values than unsalted samples. Panel preference ratings for flavour/aroma and desirability characteristics of the fish cakes were in the order: C. nigrodigitatus > O. nilotichus > E. fimbriata > I. africana > P. keolreuteri. Palmitic acid (C16:0) was the predominant saturated fatty acid in the test samples. The eicosapentaenoic acid (EPA) contents of unsalted smoke-dried C. nigrodigitatus was 4.9%, Oreochromis niloticus 6.5%, Ilisha africana 2.6%, E. fimbriata 5.6% and P. koelreuteri 7.64%. The docosahexaenoic acid (DHA) contents of salted smoked dried fish were 1.8% (C. nigrodigitatus), 4.8% (O. niloticus), 9.5% (I. africana), 5.5% (E. fimbriata) and 12.3% (P. koelreuteri).     

Effect of boiling and frying on the content of essential polyunsaturated fatty acids in muscle tissue of four fish species

Frozen samples of common fish species, sea trout (Salmo trutta), from Norway and Siberia, herring (Clupea harengus pallasi), rock sole (Lepidopsetta bilineata) and cod (Gadus morhua maris-albi), collected from a wholesale market in Krasnoyarsk city (Siberia, Russia) were analyzed. Special attention was paid to long-chain essential polyunsaturated fatty acids: eicosapentaenoic, 20:5ω3 (EPA) and docosahexaenoic, 22:6ω3 (DHA). Heat-treatment (cooking and frying) did not in general significantly decrease the contents of EPA and DHA compared to raw fish species, except for a modest reduction in Norwegian trout during frying. Boiled trout appeared to be a more valuable fish dish for obtaining the officially recommended appropriate daily intake of EPA + DHA for humans. Herring and sole had intermediate values, while boiled cod had a comparatively low value.     

Determination of methylmercury in marine and freshwater fish in Ghana using a combined technique of dithizone extraction and gas–liquid chromatography with electron capture detection

Concentrations of methylmercury (MeHg) residues were determined in different marine and freshwater fishes from Ghana. Samples were treated with ethanolic potassium hydroxide in water bath at 100 °C for 1 h. After neutralising with HCl and washing with hexane, MeHg was extracted with dithizone in toluene, cleaned up and determined by gas chromatography with electron capture detection (GC–ECD). The method was sensitive with good precision, detection limit of 0.0005 μg g⁻¹ (0.5 μg kg⁻¹) and provided good separation for organomercury compounds. The validity of the method was established using dogfish muscle certified reference material, DORM-2. The method was applied to different fish species. Concentration of MeHg in the edible muscle tissue of the tested fish ranged from 0.009 to 0.107 μg g⁻¹ wet weight. The concentrations of MeHg in the fish samples obtained do not however, constitute any significant mercury exposure to the general population through consumption of the tested fish species.     

Characterisation of furan fatty acids in Adriatic fish

Furan fatty acids (F-acids) were characterised in the fillet of European hake (Merluccius merluccius), horse mackerel (Trachurus trachurus), common sole (Solea solea), European anchovy (Engralius encrasicolus), Atlantic mackerel (Scomber scombrus), European pilchard (Sardina pilchardus) was harvested in Adriatic Sea during the spring and the summer. The main F-acids were of the saturated series: 12,15-epoxy-13-methyleicosa-12,14-dienoic acid [MonoMe(11,5)] in European hake and 12,15-epoxy-13,14-dimethyleicosa-12,14-dienoic acid [DiMe(11,5)] in all the other fish species; 12,15-epoxy-13,14-dimethyloctadeca-12,14-dienoic acid, 10,13-epoxy-11-methyloctadeca-10,12-dienoic acid and 14,17-epoxy-15,16-dimethyldocosa-14,16-dienoic acid were present in all fish species in trace amounts. Other identified F-acids were the olefinic congeners 12,15-epoxy-13,14-dimethyleicosa-12,15,16-trienoic acid and 12,15-epoxy-13,14-dimethyleicosa-10,12,14-trienoic acid. European pilchard had the highest F-acids content (30 mg/100 g fillet), whereas horse mackerel showed the lowest content (less than 0.1 mg/100 g fillet). Eicosapentaenoic acid (EPA) was positively correlated with MonoMe(11,5) and DiMe(11,5), showing that the biosynthesis of docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA) is presumably competitive with that of F-acids.     

Mercury and selenium concentrations in muscle tissue of different species of predatory freshwater fish and correlation between these elements

Concentrations of total mercury and selenium were determined in 49 and 42 muscle tissue samples, respectively, of six species of predatory freshwater fish, dace (Leuciscus leuciscus), pike perch (Sander lucioperca), pike (Esox lucius), European catfish (Silurus glanis), rainbow trout (Oncorhynchus mykiss) and asp (Aspius aspius). Muscle selenium concentration did not correlate with the corresponding total mercury concentration (R ^2?<?0.198) in all examined predatory fish species. There was an inverse correlation between the ratio Se/Hg content and the total mercury content in the muscle tissues of dace, pike perch, pike, European catfish and asp. The muscle tissue of rainbow trout exhibits a linear correlation between the ratio Se/Hg content and the total mercury content. The total mercury concentration of all examined samples did not exceed the hygienic limit for Hg for predatory fish.     

Seasonal variation in the fatty acid composition of three Mediterranean fish – sardine (Sardina pilchardus), anchovy (Engraulis encrasicholus) and picarel (Spicara smaris)

The total fat contents and the fatty acid compositions of three common Mediterranean fish, namely sardine (Sardina pilchardus), anchovy (Engraulis encrasicholus) and picarel (Spicara smaris) were determined at bimonthly intervals for a one-year period. The purpose of this work was to study the seasonal variation of the fatty acids in the three fish that are some of the best sources of n − 3 fatty acids. The fat and fatty acid content of the investigated fish species show a significant seasonal dependency. Two of the fish (anchovy and picarel) have the highest fat content during the late winter – spring period. On the other hand, sardine shows the highest fat concentrations during the spring-early summer period. The fish that showed the highest variation in fatty acid composition was the anchovy. The sardine was found to be the best source of n − 3 fatty acids during the one-year period (35.35 g/100 g fatty acids). Finally the picarel had the highest oleic acid content (on average, 13.89/100 g fatty acids).     

Effect of freezing on theβ-hydroxyacyl-CoA-dehydrogenase (HADH) activity of fish meat

Changes in the β-hydroxyacyl-CoA-dehydrogenase (HADH) activity of squid (Loligo vulgaris), mackerel (Scomber scombrus), tuna (Thunnus alalunga), sea bream (Pagellus centrodontus), sole (Solea solea), hake and small hake (Merluccius merluccius) meat due to freezing treatment at ?10° C, ?18° C, ?35° C, ?80° C or ?196° C were investigated. With the exception of the small hake, the HADH activity of aqueous extracts from meat was significantly higher (p<0.0001) in all frozen/thawed fish species studied than in unfrozen animals because during freezing there was a release of HADH. HADH activity values of frozen/thawed squid, unfrozen mackerel, frozen/thawed and unfrozen sea bream and unfrozen hake were affected by the storage time in crushed ice.     

Changes in histamine and volatile amines in six commercially important species of fish of the Thoothukkudi coast of Tamil Nadu,India stored at ambient temperature

Six commercially important species of fish, i.e. mackerel (Rastrelliger kanagurta), sardine (Sardinella fimbriata), emperor bream (Lethrinus miniatus), threadfin bream (Nemipterus japonicus), trevally (Carangoides armatus) and barracuda (Sphyraena barracuda) of the Thoothukkudi coast of Tamil Nadu, India, were examined for changes in histamine and volatile amines (TVB-N and TMA-N) under ambient temperature storage (32±2 °C). Fish were organoleptically acceptable up to 15 h of storage, except emperor bream that spoiled after 12 h of storage. Histamine and volatile amines increased progressively on storage, but the rate of change varied with the species of fish. The TVB-N content of barracuda and emperor bream exceeded the acceptable limit of 35 mg/100 g after 15 h of storage while, in other fishes, their formation was slow. However, the TMA-N contents of all the fishes were above 10 mg/100 g after 15 h of storage. The TMA-N content of fish was found to correlate more closely with the sensory changes than the TVB-N content. With regard to the histamine toxicity, the histamine content was above the USFDA maximum allowable limit of 50 ppm in mackerel after 12 h, and, in sardine and trevally, after 15 h of storage. The histamine content did not show any correlation with the sensory changes or with the content of volatile amines. In trevally, it was noted that the histamine formation was very high and similar to that of mackerel. It is therefore concluded that the mackerel, sardine and trevally could cause histamine toxicity problems before they become organoleptically unacceptable.