Cod Samples Research Articles

High-intensity ultrasound treatment of Atlantic cod: Impact on nutrients, structure, sensory quality, bioactivity, and in-vitro digestibility

This study evaluates the impact of high-intensity ultrasound (HIU) on the physicochemical properties and in-vitro digestibility of Atlantic cod (Gadus morhua). Various ultrasound durations (0–60 min) were applied to assess changes in color attributes, total antioxidant capacity (TAC), total flavonoid content (TFC), total phenolic content (TPC), total protein content, and in-vitro protein digestibility (IVPD). Results indicated HIU maximumly increased TAC, TFC, TPC, and peptide content before digestion by 7.28 % (US60), 3.00 % (US30), 32.43 % (US10), and 18.93 % (US60), respectively. While HIU reduced total protein content, it enhanced IVPD by up to 12.24 % (US30). Color attributes electron microscopy reflected structural changes in the cod samples, suggesting the effectiveness of HIU in altering protein structures. These findings highlight HIU’s potential as a non-thermal technique for improving the sensory and nutritional quality of Atlantic cod, offering valuable insights for the seafood processing industry and consumers.

Quality changes in cod (Gadus morhua) and redfish (Sebastes marinus) loins and tails during frozen storage

The muscle structure and composition may vary along the different portions of fish fillets, which can complicate the quality and storage stability of products. Loins and tails from Atlantic cod (Gadus morhua) and redfish (Sebastes marinus) fillets were therefore stored at −25 °C up to 16 months and 20 months, respectively, to investigate the quality changes influenced by the duration of frozen storage within the fillet portions. Throughout the storage period, the loss of total sulfhydryl groups correlated with increased disulfide bonds, indicating partial oxidative protein degradation. This may be linked with protein denaturation as evidenced by the decrease of soluble proteins, as well as decreased water holding capacity and increased thawing drip loss and cooking loss. The results from the cod samples reveal that stronger degradation changes occurred in the tail. The loin, therefore, had more storage stability as well as higher nutritional value. However, other quality attributes were similar between the two portions in the redfish fillets. Higher free fatty acid (FFA) values, lower soluble protein contents, and higher disulfide bond contents were obtained in the cod samples compared to the redfish samples at the same storage time, indicating that lipid hydrolysis and protein degradation effects were stronger in the cod (lean fish) compared to redfish (medium fat species).

Accumulation and dietary risks of perfluoroalkyl substances in fish and shellfish: A market-based study in Barcelona

Since the 1940s, per- and polyfluoroalkyl substances (PFAS) have been widely produced and used in various applications due to their unique properties. Consequently, the principal exposure routes of PFAS have been broadly studied, leading to the conclusion that dietary exposure (more specifically, the consumption of fish and seafood) was one of their main contributors. Thus, developing an analytical method that determines the level of PFAS in fish and seafood has become a relevant subject. In this work, a previous analytical method has been optimized to determine 12 PFAS in fish muscle from salmon, tuna, cod, hake, sardine, anchovy, and sole, as well as in seven different seafood species (i.e., cuttlefish, octopus, squid, shrimp, Norway lobster, prawn, and mussel) by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Subsequently, the PFAS profile of the different species was studied to determine if it was consistent with that previously reviewed in the literature and to know the most relevant contribution of PFAS for each species. Finally, human exposure to PFAS through their consumption was estimated by the daily intake for seven different age/gender groups.PFAS were obtained from 0.014 to 0.818 ng g−1 wet weight in fish samples. Sardines, anchovies, and soles presented the highest PFAS levels. However, cod samples also showed some PFAS traces. Regarding seafood, PFAS levels range from 0.03 to 36.7 ng g−1 dry weight for the studied species. A higher concentration of PFAS has been found in the cephalopods' spleens and the crustaceans' heads. PFOS and PFBS were the predominant compounds in each seafood species, respectively. On the other hand, in the case of mussels, which are the less polluted species of the study, contamination by longer-chained PFAS was also observed.Finally, the total intake of PFAS due to fish and shellfish consumption for the Spanish adult population was estimated at 17.82 ng day−1. Nevertheless, none of the analyzed samples exceeded the European Food Safety Authority (EFSA) risk value for the supervised PFAS in any age/gender group reviewed.

Winter Water Quality Modeling in Xiong'an New Area Supported by Hyperspectral Observation.

Xiong'an New Area is defined as the future city of China, and the regulation of water resources is an important part of the scientific development of the city. Baiyang Lake, the main supplying water for the city, is selected as the study area, and the water quality extraction of four typical river sections is taken as the research objective. The GaiaSky-mini2-VN hyperspectral imaging system was executed on the UAV to obtain the river hyperspectral data for four winter periods. Synchronously, water samples of COD, PI, AN, TP, and TN were collected on the ground, and the in situ data under the same coordinate were obtained. A total of 2 algorithms of band difference and band ratio are established, and the relatively optimal model is obtained based on 18 spectral transformations. The conclusion of the strength of water quality parameters' content along the four regions is obtained. This study revealed four types of river self-purification, namely, uniform type, enhanced type, jitter type, and weakened type, which provided the scientific basis for water source traceability evaluation, water pollution source area analysis, and water environment comprehensive treatment.

Isotopic turnover in polar cod (Boreogadus saida) muscle determined through a controlled feeding experiment.

Polar cod (Boreogadus saida) is an important trophic link within Arctic marine food webs and is likely to experience diet shifts in response to climate change. One important tool for assessing organism diet is bulk stable isotope analysis. However, key parameters necessary for interpreting the temporal context of stable isotope values are lacking, especially for Arctic species. This study provides the first experimental determination of isotopic turnover (as half-life) and trophic discrimination factors (TDFs) of both δ13 C and δ15 N in adult polar cod muscle. Using a diet enriched in both 13 C and 15 N, we measured isotopic turnover times of 61 and 49 days for δ13 C and δ15 N, respectively, with metabolism accounting for >94% of the total turnover. These half-life estimates are valid for adult polar cod (>3 years) experiencing little somatic growth. We measured TDFs in our control of 2.6‰ and 3.9‰ for δ13 C and δ15 N, respectively, and we conclude that applying the commonly used TDF of ~1‰ for δ13 C for adult polar cod may lead to misrepresentation of dietary carbon source, while the use of 3.8‰ for δ15 N is appropriate. Based on these results, we recommend that studies investigating seasonal shifts in the diet of adult polar cod sample at temporal intervals of at least 60 days to account for isotopic turnover in polar cod muscle. Although isotopic equilibrium was reached by the fish in this study, it was at substantially lower isotope values than the diet. Additionally, the use of highly enriched algae in the experimental feed caused very high variability in diet isotope values which precluded accurate calculation of TDFs from the enriched fish. As a result of the challenges faced in this study, we discourage the use of highly enriched diets for similar experiments and provide recommendations to guide the design of future isotopic turnover experiments.

Evaluating dried salted cod amino acid signature for nutritional quality assessment and discriminant analysis.

Thus, the aim of this study was to answer three scientific questions: (1) Are the protein content and amino acid profile of dried salted cod influenced by species (Gadus morhua and Gadus macrocephalus)? (2) Are the protein content and amino acid profile of dried salted cod influenced by the geographical area of capture (Iceland and Norway)? and (3) Does the amino acid profile have the potential to be used as a discriminator of species and geographical areas of capture? A total of 45 dried salted cods (2-3 kg of dry weight; n = 15 samples/origin) were used in this study. The Atlantic cod was fished in the Atlantic northeast (FAO 27 area) within the Exclusive Economic zones (EEZ) of Norway (n = 15) and Iceland (n = 15), while the Pacific cod was caught in the Pacific northeast (FAO 67 area) within the Alaska EEZ (n = 15). Total protein content was determined by the Kjeldahl method, in accordance with the AOAC procedures. The amino acid profile was analyzed by HPLC with fluorescence detection (at excitation and emission wavelengths of 338 and 425 nm, respectively). The Atlantic cod presented higher contents of total protein (33.90 versus 33.10 g/100 g of cod edible portion; p = 0.017) and total amino acid contents (32.52 versus 32.04 g/100 g of cod edible portion; p = 0.015) but displayed lower percentage of indispensable amino acids (32.16 versus 32.83 g/100 g of protein; p < 0.001) than Pacific cod. Among the Atlantic cod harvesting locations, the Norwegian cod displayed higher total amino acid contents (96.91 versus 96.81 g/100 g of protein; p = 0.012) and higher percentage of indispensable amino acids (35.38 versus 28.94 g/100 g of protein; p = 0.042) than the Icelandic counterpart. A correct classification of 100% was obtained for the Pacific and Icelandic cod varieties, but the classification accuracy in the Norwegian cod was of just 86.67%, since 2 samples out of 15 were incorrectly classified as Icelandic. The comparison of cod species showed that the Atlantic cod had a significantly lower EAAI than the Pacific cod (p < 0.001; 88.23 versus 88.61). On the other hand, the comparison of the two origins in the Atlantic cod, showed that Norwegian cod displayed a significantly higher EAAI than the Icelandic cod (99.15 versus 77.32). The assessment of the EAAI allows the classification of the protein's nutritional quality, allowing us to classify both cod species as a good protein source to human diet. However, within the Atlantic cod, the Norwegian cod's protein is classified as high quality, while the Icelandic cod attain the classification of useful quality. Regarding the amino acid profile discriminatory potential to classify cod samples. The results show that the AA profile has 100% accuracy in the separation of cod species, but was not globally efficient in the differentiation of the Norwegian from the Icelandic cod.

Effect of High Hydrostatic Pressure Processing on the Microbiological Quality and Bacterial Diversity of Sous-Vide-Cooked Cod

High hydrostatic pressure (HP) is a promising method to improve the microbiological quality of sous-vide foods. Monitoring the composition and behavior of the microbial communities in foods is of most importance for the production of high-quality and safe products. High-throughput sequencing (HTS) provides advanced approaches to determine food's microbial community composition and structure. The aim of the present study was to determine the impact of different HP treatments on the microbial load and bacterial diversity of sous-vide Atlantic cod. Sous-vide cooking at 57.1 °C for 30 min followed by HP treatment at 500 MPa for 8 min reduced viable cell counts (total aerobic mesophiles) in the cod samples below detectable levels for 45 days of storage under refrigeration. In a second trial with cod cooked sous-vide at 52 °C for 20 min followed by HP treatments at 300 or 600 MPa (with HP treatment temperatures of 22 °C or 50 °C for 4 or 8 min, depending on treatment), only the treatments at 600 MPa delayed bacterial growth for at least 30 days under refrigeration. The optimal HP conditions to improve the microbiological quality of sous-vide cod cooked at low temperatures were obtained at 600 MPa for 4 min at a pressurization temperature of 50 °C. Bacterial diversity was studied in cod cooked sous-vide at 52 °C for 20 min by HTS. In the absence of HP treatment, Proteobacteria was the main bacterial group. A succession of Pseudomonadaceae (Pseudomonas) and Enterobacteriaceae was observed during storage. Firmicutes had low relative abundances and were represented mainly by Anoxybacillus (early storage) and Carnobacterium (late storage). The HP-treated sous-vide cod showed the greatest differences from controls during late storage, with Aerococcus and Enterococcus as predominant groups (depending on the HP conditions). The application of HTS provided new insights on the diversity and dynamics of the bacterial communities of sous-vide cod, revealing the presence of bacterial genera not previously described in this food, such as Anoxybacillus. The significance of Anoxybacillus as a contaminant of seafoods should be further investigated.

A novel fluorescence resonance energy transfer (FRET)-based paper sensor with smartphone for quantitative detection of Vibrio parahaemolyticus

In recent years, food poisoning events caused by Vibrio parahaemolyticus have shown an upward trend. Therefore, there is a growing need for a rapid, sensitive and simple detection method for V. parahaemolyticus . The aim of this study was to develop a novel aptamer-based paper sensor for the rapid, sensitive, portable and specific detection of V. parahaemolyticus in seafood through the fluorescence resonance energy transfer (FRET) principle. The capture probes for this strategy were made by chemically coupling carbon dots (CDs) to amino-modified single-stranded DNA. Switches were double-stranded DNA formed by hybridization of anti- V. parahaemolyticus aptamers (aptamer) and gold nanoparticles (AuNPs)-probes. Once V. parahaemolyticus was introduced, the aptamer in the double-stranded DNA bound specifically to the target bacteria and the sensor was ‘On’, releasing the AuNPs-probes to bind to the capture probes. The fluorescence color of the CDs changed significantly from bright blue to colorless because of the FRET between CDs and AuNPs. As expected, when filter paper was used as the assay liquid carrier, an ingenious FRET-based paper sensor was presented for accurate field reporting of V. parahaemolyticus , with a linear range of 10 1 -10 6 cfu/mL. This strategy has a detection limit of 8.9 cfu/mL for V. parahaemolyticus in culture and 6.7 × 10 1 cfu/mL in artificially contaminated cod samples. The results indicate that this study has good potential as a new portable sensor for the detection of V. parahaemolyticus in complex food matrices. • Novel FRET-based paper strip was developed to detect Vibrio parahaemolyticus. • FRET-based paper strip with smartphone for field detection of Vibrio parahaemolyticus. • Fast response time, high sensitivity and specificity of this sensor for Vibrio parahaemolyticus. • The sensor has good practicability in fish samples.

Separated by Space and Time but United by Kinship: Phylogeographical and Phylogenetic History of Two Species of Eleginus (Gadidae) Based on the Polymorphism of Cyt b Mitochondrial DNA Gene

Fishes of the genus Eleginus (Gadidae) are typical representatives of the ichthyofauna of the Northern Hemisphere; they play an important trophic role in the marine ecosystems of the Arctic and North Pacific and serve as targets of commercial and artisanal coastal fishing in many areas of the Russian North and Far East, as well as in areas of the coast of Alaska and northern Japan. The level of knowledge about the intraspecific organization of representatives of the genus Eleginus that is necessary for the rational exploitation of their stocks remains insufficient and their interspecific relationships have so far been analyzed using limited materials. This paper presents the first study of the interspecific relationships and intraspecific structure of navaga (E. nawaga) and saffron cod (E. gracilis) using a large-scale material (986 specimens in 29 samples from most of the species ranges) based on analysis of the polymorphism of mtDNA gene Cyt b. It is shown that they are independent, genetically differentiated species and their comparison with representatives of the genus Microgadus indicates that both species of the genus Eleginus might originate from a common ancestor close to M. proximus, while the divergence in the genus Microgadus occurred much earlier. Data on the haplotypic composition of saffron cod samples inhabiting areas from the Peter the Great Bay to Alaska waters and navaga samples inhabiting areas from the White Sea to the Ob Bay of the Kara Sea are given, which makes it possible to consider the phylogeographic history of both species and their intraspecific organization within the studied areas. Three groups can be distinguished for saffron cod: (1) Pacific–Japanese–Sakhalin group, (2) Chukchi–Bering seas group, and (3) intermediate group, which includes samples from the Sea of Okhotsk and waters of the northern Kurils.

Polymorphism of mtDNA gene Cyt b of the Chukchi Sea polar cod, Boreogadus saida (Gadidae, Gadiformes)

Polar cod (Boreogadus saida) is a species with an extensive pan-Arctic distribution. Although it is not an important target of commercial fisheries, due to its extremely high abundance and as a keystone species linking zooplankton with higher trophic levels of mammals and birds, polar cod are considered a critical component of the Arctic Ocean pelagic ecosystem. For the Chukchi and Beaufort Seas, either a complete absence of a population structure or very weak differences between this part of its range and others is shown. The purpose of this work is to identify the intraspecific organization of the polar cod based on mtDNA from most areas of the Chukchi Sea and the adjacent part of the Beaufort Sea. This is the first presentation of results from analysis of the Cytb gene polymorphism of mitochondrial DNA in samples of polar cod from the western Chukchi Sea. Results indicated that there is no genetic differentiation of polar cod in the surveyed area. The exception are several samples from the Kotzebue Sound, central Chukchi Sea and western Beaufort Sea, which may be due to the transport of polar cod eggs, larvae or early juveniles by currents from the spawning grounds of Kotzebue Sound first to the central Chukchi Sea, and then to the western Beaufort Sea. The Kotzebue Sound population differs in nucleotide diversity index, as well as in pairwise values of the FST genetic differentiation index, which may be due to the isolation of this site from main currents in the area.

Effects of E-beam irradiation on the physicochemical properties of Atlantic cod (Gadus morhua)

Electron beam (E-beam) irradiation can effectively inactivate severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in cold-chain seafood. This study evaluated the effects of E-beam irradiation at doses killing SARS-CoV-2 on quality indicators of Atlantic cod. The cod samples were exposed to 0, 2, 4, 7, and 10 kGy E-beam irradiation, and nutrition, texture, color, and sensory attributes were investigated. The results showed that E-beam irradiation significantly increased thiobarbituric acid (TBA) value and decreased hardness, chewiness, and a* value of Atlantic cod (P < 0.05). E-beam irradiation with 10 kGy significantly lowered total volatile base nitrogen (TVB-N) and reducing sugar content while increasing moisture and ash content (P < 0.05). A significant color change was observed after irradiation with 2 kGy–7 kGy E-beam (P < 0.05). E-beam irradiation had no effects on sensory attributes (P > 0.05). A dose of 4 kGy was recommended considering the keeping quality in Atlantic cod.

Probing 1D convolutional neural network adapted to near-infrared spectroscopy for efficient classification of mixed fish

Salmon and Cod are economically significant world-class fish that have high economic value. It is difficult to accurately sort and process them by appearance during harvest and transportation. Conventional chemical detection means are time-consuming and costly, which greatly affects the cost and efficiency of Fishery production. Therefore, there is an urgent need for smart Fisheries methods which use for the classification of mixed fish. In this paper, near-infrared spectroscopy (NIRS) was used to assess salmon and cod samples. This study aims to evaluate feasibility of a back-propagation neural network (BPNN) and a convolutional neural network (CNN) for identifying different species of fishes by the corresponding spectra in comparison to traditional chemometrics Partial Least Squares. After comparing the effects of different batch sizes, number of convolutional kernels, number of convolutional layers, and number of pooling layers on the classification of NIRS spectra comparing different structures of one-dimensional (1D)–CNN, we propose the 1D-CNN-8 model that is most suitable for the classification of mixed fish. Compared with the results of traditional chemometrics methods and BPNN, the prediction model of the 1D-CNN model can reach 98.00% Accuracy and the parameters are significantly better than others. Meanwhile, the parameters and floating-point operations of the optimal model are both small. Therefore, the improved CNN model based on the NIRS can effectively and quickly identify different kinds of fish samples and contribute to realizing edge computing at the same time.

Dry‐salted cod (Gadus morhua) rehydration assisted by pulsed electric fields: modelling of mass transfer kinetics

BACKGROUNDDry‐salted cod (Gadus morhua) must be rehydrated before consumption and this step can take up to 5 days. Desalting of cod on an industrial scale poses many problems, mainly related to the long processing times and the quality of the final product. For this reason, many researchers have focused on finding new desalting methods to improve mass transfer. The application of pulsed electric fields (PEF) has been proposed as an alternative method for improving mass transfer in many food processes. However, there is no previous literature on the use of PEF to improve animal tissue rehydration. Therefore, the present study aimed to investigate the influence of two PEF pre‐treatments [PEF (1) 500 V cm−1 and PEF (2) 1000 V cm−1] on mass transport kinetics during the rehydration process of salted cod. The rehydration process was carried out under static conditions for 6 days, immersing dry‐salted cod samples in tap water (5 ± 0.5 °C).RESULTSThe results show that the use of PEF technology increases the rate of the rehydration process of dry‐salted cod and influences the redistribution of salt. In general, the samples pre‐treated with PEF showed higher weight gain and lower salt loss than the control samples during the rehydration process.CONCLUSIONThe application of PEF prior to rehydration of salted cod samples could be of interest to the food industry as a result of a higher process yield (higher weight gain) and the possibility to reduce the water renewal because less NaCl is lost in the wastewater. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

A Multi-Sensor System for Sea Water Iodide Monitoring and Seafood Quality Assurance: Proof-of-Concept Study.

Iodine is a trace chemical element fundamental for a healthy human organism. Iodine deficiency affects about 2 billion people worldwide causing from mild to severe neurological impairment, especially in children. Nevertheless, an adequate nutritional intake is considered the best approach to prevent such disorders. Iodine is present in seawater and seafood, and its common forms in the diet are iodide and iodate; most iodide in seawater is caused by the biological reduction of the thermodynamically stable iodate species. On this basis, a multisensor instrument which is able to perform a multidimensional assessment, evaluating iodide content in seawater and seafood (via an electrochemical sensor) and discriminating when the seafood is fresh or defrosted quality (via a Quartz Micro balance (QMB)-based volatile and gas sensor), is strategic for seafood quality assurance. Moreover, an electronic interface has been opportunely designed and simulated for a low-power portable release of the device, which should be able to identify seafood over or under an iodide threshold previously selected. The electrochemical sensor has been successfully calibrated in the range 10–640 μg/L, obtaining a root mean square error in cross validation (RMSECV) of only 1.6 μg/L. Fresh and defrosted samples of cod, sea bream and blue whiting fish have been correctly discriminated. This proof-of-concept work has demonstrated the feasibility of the proposed application which must be replicated in a real scenario.

High occurrence of Anisakidae at retail level in cod (Gadus morhua) belly flaps and the impact of extensive candling

The presence of Anisakidae at retail level, after the routine screening via candling, was investigated in cod, the most commonly consumed fish species in Belgium. A total of 780 pre-packed belly flap samples destined for one branch of retail shops were collected from a Belgian wholesale company. To recover all larvae, each sample was first candled and thereafter enzymatically digested. Larvae were morphologically identified to the genus level and a subset was additionally molecularly confirmed by amplification of the ITS fragment and HinfI/HhaI enzyme restriction. The PCR/RFLP profiles of Contracaecum spp. were determined and confirmed with sequencing by the European Reference Laboratory for Parasites (Istituto Superiore di Sanità). The positivity rate of Anisakidae in the individual cod samples was 18% [95%-CI: 15–21%], with a mean intensity of one larva [range: 1–6]. Belly flaps were sold packed primarily by two, with a one-in-three chance of buying an infected package. Pseudoterranova spp. infections (single infections) were most frequently detected (positivity rate 9% [95%-CI: 7–11]), closely followed by Anisakis spp. (7% [95%-CI: 6–9]). Co-infections of Pseudoterranova spp. and Anisakis spp. comprised 8% of the infections, with a positivity rate of 1% [95%-CI: 1–3%]. All belly flaps reportedly were candled prior to our sampling, nonetheless our results indicated that an additional candling screening before packaging would identify an extra third of the infections and larvae. In 19 of the 139 infected samples, all larvae were recovered by the additional candling, thereby removing the infection risk for consumers. In conclusion, this study shows that cod belly flaps infected with zoonotic parasites reach the Belgian consumer. Although a second candling step at retail level could be helpful in reducing the consumer risk, additional measures are needed since 66% of infections would still remain undetected.

Genomic analysis reveals neutral and adaptive patterns that challenge the current management regime for East Atlantic cod Gadus morhua L.

Challenging long‐held perceptions of fish management units can help to protect vulnerable stocks. When a fishery consisting of multiple genetic stocks is managed as a single unit, overexploitation and depletion of minor genetic units can occur. Atlantic cod (Gadus morhua) is an economically and ecologically important marine species across the North Atlantic. The application of new genomic resources, including SNP arrays, allows us to detect and explore novel structure within specific cod management units. In Norwegian waters, coastal cod (i.e. those not undertaking extensive migrations) are divided into two arbitrary management units defined by ICES: one between 62° and 70°N (Norwegian coastal cod; NCC) and one between 58° and 62°N (Norwegian coastal south; NCS). Together, these capture a fishery area of >25,000 km2 containing many spawning grounds. To assess whether these geographic units correctly represent genetic stocks, we analysed spawning cod of NCC and NCS for more than 8,000 SNPs along with samples of Russian White Sea cod, north‐east Arctic cod (NEAC: the largest Atlantic stock), and outgroup samples representing the Irish and Faroe Sea's. Our analyses revealed large differences in spatial patterns of genetic differentiation across the genome and revealed a complex biological structure within NCC and NCS. Haplotype maps from four chromosome sets show regional specific SNP indicating a complex genetic structure. The current management plan dividing the coastal cod into only two management units does not accurately reflect the genetic units and needs to be revised. Coastal cod in Norway, while highly heterogenous, is also genetically distinct from neighbouring stocks in the north (NEAC), west (Faroe Island) and the south. The White Sea cod are highly divergent from other cod, possibly yielding support to the earlier notion of subspecies rank.

Analysis of sulfonamides, fluoroquinolones, tetracyclines, triphenylmethane dyes and other veterinary drug residues in cultured and wild seafood sold in Montreal, Canada

Freshwater and marine seafood products purchased in Montreal, Canada, were screened for diverse veterinary drug residues including sulfonamides and potentiators, macrolides, lincosamides, nitrofurans, nitroimidazoles, amphenicols, quinolones and fluoroquinolones, one triphenylmethane dye and its leuco-metabolite, and tetracyclines. QuEChERS extraction ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) was validated in three model matrices (fatty fish, lean fish, and shrimp edible meat). Method detection limits were in the range of 0.002–3 μg/kg, and the accuracy of matrix-matched extracted calibrants was generally within acceptance criteria. The aquaculture or wild-caught samples of pangasius (basa), cod, salmon, sole, tilapia, trout, white shrimp and giant tiger prawn originated from Canada, China, India, Southeast Asia (Indonesia, Thailand, Vietnam), and other regions worldwide. Overall, 38 % of the tested fish and shrimp samples had detectable residues of at least one veterinary drug or metabolite, and 25 % were not compliant to Canadian guidelines. Leucomalachite green was detected across various sample types (detection frequency: 13 %; maximum: 0.9 μg/kg). Other detected compounds (2–11 % of samples) included tetracycline (maximum: 36 μg/kg), 4-epi-oxytetracycline (18 μg/kg), oxytetracycline (13 μg/kg), metronidazole (13 μg/kg), sulfamethazine (4.8 μg/kg), sulfamethoxazole (4.2 μg/kg), trimethoprim (0.59 μg/kg), florfenicol (0.27 μg/kg), flumequine (0.21 μg/kg), enrofloxacin (1.6 μg/kg), and ofloxacin (0.52 μg/kg).

Predicting liquid loss of frozen and thawed cod from hyperspectral imaging

As the ability to appraise the quality of every fish in a delivery in a consistent, objective, and rapid manner has numerous advantages for both sellers and buyers, there has been much research into methods to achieve this. One possible proxy for quality assessment is liquid loss, which correlates with undesirable sensory attributes. This study evaluated whether hyperspectral imaging could predict liquid loss on samples that had undergone a program of freezing and thawing. Vacuum-packaged cod loins were split into two groups, one which was kept chilled and the other that underwent a program of freezing and thawing. Multivariate analysis of the hyperspectral imaging data on the chilled samples could predict liquid loss with good accuracy for samples that underwent no further processing. Analysis of data from the hyperspectral images of the frozen and thawed cod samples also showed a good ability to predict their liquid loss. These results indicate that hyperspectral imaging is a promising method for non-invasive quality monitoring of cod products in different processing states. Also, whereas previous research had been unable to predict sample processing protocols, improvements to the hyperspectral imaging technology now enables identification of samples based on freezing and thawing procedures.

A high-quality genetic reference database for European commercial fishes reveals substitution fraud of processed Atlantic cod (Gadus morhua) and common sole (Solea solea) at different steps in the Belgian supply chain

Seafood is an important component of the human diet. With depleting fish stocks and increasing prices, seafood is prone to fraudulent substitution. DNA barcoding has illustrated fraudulent substitution of fishes in retail and restaurants. Whether substitution also occurs in other steps of the supply chain remains largely unknown. DNA barcoding relies on public reference databases for species identification, but these can contain incorrect identifications. The creation of a high quality genetic reference database for 42 European commercially important fishes was initiated containing 145 Cytochrome c oxidase subunit I (COI) and 152 Cytochrome b (cytB) sequences. This database was used to identify substitution rates of Atlantic cod (Gadus morhua) and common sole (Solea solea) along the fish supply chain in Belgium using DNA barcoding. Three out of 132 cod samples were substituted, in catering (6%), import (5%) and fishmongers (3%). Seven out of the 41 processed sole samples were substituted, in wholesale (100%), food services (50%), retailers (20%) and catering (8%). Results show that substitution of G. morhua and S. solea is not restricted to restaurants, but occurs in other parts of the supply chain, warranting for more stringent controls along the supply chain to increase transparency and trust among consumers.

Colorimetric detection of Gadidae species using probe-modified gold nanoparticles

Codfish is an essential part of the world's marine fishery resources. It contains several commercially important species. The aim of the present work is to develop a rapid codfish colorimetric detection system based on gold nanoparticles (AuNPs) and a specific probe targeting the 12S rDNA of Gadidae species. Three cod species from Gadidae family (Gadidae morhua, G. macrocephalus and Melanogrammus aeglefinus) were selected as the target species in this colorimetric detection system. No positive results were obtained when non-Gadidae samples challenged this system, indicating its high specificity. The detection limit of G. morhua, G. macrocephalus and M. aeglefinus was 2.2, 3.15 and 2.65 ng/μL, respectively. Furthermore, 20 commercial cod samples were detected by this method, and the results were consistent with those of obtained by PCR and DNA sequencing. As the results were judged by the naked eye and detection performed in fast mode (less than 30 min), the 12S rDNA-probe-AuNPs system had strong applicability, and thus it would facilitate further advances in food species authentication.