Fish Fillets Research Articles

Effect of konjac glucomannan-based preservation pads on quality changes in refrigerated large yellow croaker (Pseudosciaena crocea)

The purpose of this study was to evaluate the preservation effects of konjac glucomannan (KGM)/oregano essential oil (OEO) Pickering emulsion-based pads (K/OPE pads) on large yellow croaker (Pseudosciaena crocea) fillets stored at 4 °C. The K/OPE pads were fabricated using a freeze-drying technique. The homogeneous distribution of the OEO Pickering emulsions in the KGM matrix was observed using scanning electron microscopy. Fourier transform infrared spectroscopy confirmed that the OEO emulsions were encapsulated in the KGM and there was hydrogen bonding interaction between them. Compared with the KGM pads, the K/OPE pad groups demonstrated enhanced antioxidant and antimicrobial properties. When the content of OPE was increased from 20 % to 40 %, the antioxidant performance of the K/OPE pads increased from 48.09 % ± 0.03 % to 86.65 % ± 0.02 % and the inhibition range of Escherichia coli and Staphylococcus aureus increased to 13.84 ± 0.81 and 16.87 ± 1.53 mm, respectively. At the same time, K/OPE pads were more effective in inhibiting the formation of total volatile alkaline nitrogen and the production of thiobarbituric acid-reactive substances, thereby helping in reducing water loss and maintaining the muscle tissue structure of fish fillets for a longer storage time. Consequently, these K/OPE40 pads extended the shelf life of the fish fillets by an additional 4 days and delayed spoilage during refrigerated storage. The findings suggest that the K/OPE pads can effectively safeguard the quality of refrigerated large yellow croaker fillets, presenting their potential as an active packaging material in the fish preservation industry.

Efficient and sustainable production of intelligent nonwovens as indicators of food spoilage through solution blow spinning of proteins and natural pigments from agri-food waste

The efficient manufacturing of food spoilage indicators based on intelligent nonwovens represents a promising alternative to enable the application of these materials in food quality monitoring. The objective of this study was to rapidly produce intelligent nanofiber nonwovens made of zein/gelatin (Z/G) functionalized with various concentrations (5–15% w/w on the matrix) of anthocyanin-rich food-residue extracts from purple cabbage (CAE) or purple sweet potato (PAE) using the solution-blow-spinning (SBS) technique for use in food-quality-monitoring applications. The addition of CAE or PAE to the Z/G matrix reduced the viscosity of the solution and (consequently) the nanofiber diameters from 999 nm to 882 and 583 nm, respectively. Such incorporation also improved the mechanical, thermal, and water-related properties of the nanofibers and endowed them with antioxidant capacities. Nonwovens composed of Z/G nanofibers with added CAE or PAE, especially at concentrations of 15%, exhibited visible color changes (ΔE ≥ 3) that rapidly altered in response to pH (3–10) and when exposed to ammonia vapor. The nonwovens were successfully used to monitor the deterioration of pasteurized milk and fish fillets. They reveal a visual color change from pink at 0 h to a more intense pink at 48 h in response to milk deterioration and a color change from pink at 0 h to light brown after 48 h when the fish fillets were considered deteriorated. The use of these nanofiber nonwovens to monitor changes in food quality highlights the significant potential of the SBS technique and the use of anthocyanins from agri-food waste to produce new intelligent packaging materials for use in food applications.

Microplastics and Anthropogenic Particles in Recreationally Caught Freshwater Fish from an Urbanized Region of the North American Great Lakes.

Microplastics are a pervasive contaminant cycling through food webs-leading to concerns regarding exposure and risk to humans. We aimed to quantify and characterize anthropogenic particle contamination (including microplastics) in fish caught for human consumption from the Humber Bay region of Lake Ontario. We related quantities of anthropogenic particles to other factors (e.g., fish size) that may help in understanding accumulation of microplastics in fish. A total of 45 samples of six fish species collected from Humber Bay in Lake Ontario near Toronto, Ontario, Canada, were examined for anthropogenic particles in their gastrointestinal (GI) tracts and fillets. Using microscopy and spectroscopy, suspected anthropogenic particles were identified and characterized. We observed anthropogenic particles in the GI tracts and fillets of all species. Individual fish had a of anthropogenic particles, with a single fish containing up to 1,508 particles. GI tracts had particles/fish ( particles/gram), and fillets had particles/fish ( particles/gram). Based on a consumption rate of 2 servings/week, the average yearly human exposure through the consumption of these fish fillets would be particles. Our findings suggest that consumption of recreationally caught freshwater fish can be a pathway for human exposure to microplastics. The elevated number of particles observed in fish from Humber Bay highlights the need for large-scale geographic monitoring, especially near sources of microplastics. Currently, it is unclear what the effects of ingesting microplastics are for humans, but given that recreationally caught freshwater fish are one pathway for human exposure, these data can be incorporated into future human health risk assessment frameworks for microplastics. https://doi.org/10.1289/EHP13540.

Absence of microplastic bioaccumulation in cod fillets from plastic-polluted western Norwegian waters

Plastics are synthetic, persistent materials that are distributed worldwide. An important concern is whether microplastics (MP) can bioaccumulate in the food chain and pose a threat to human consumers. We studied MP in the fillet of resident coastal cod from a plastic-polluted area in Western Norway, where long-range transported marine litter accumulates and MP are generated on shore. We dissected the fish and processed the samples in an MP-free lab using gentle enzymatic treatment. Micro Fourier transform infrared spectroscopy (µFTIR) was used for identification of particles down to 10 µm. The fish were 40 to 74 cm, corresponding to 2-6 years old. 29 particles were observed in fillets from eight of the 23 individuals. The mean particle count was 1.55 ± 2.75 nMP/100 g, and the mean concentration was 2.81 ± 8.33 µg/kg wet weight. Six polymer groups were identified, where polypropylene (33%) and polyethylene (30%) were the most frequent. The majority (86%) of the particles were fragments ranging from 32-100 µm. Fibers and fragments over 200 µm were observed. The largest particle was a PP particle of 258.2 µm. Controls showed minimal contamination and the procedural blanks were negative. There was no significant correlation between age, body condition, time of capture, and MP concentrations, and no evidence of bioaccumulation of MP in the fillet of older fish after in situ exposure. MP in food is of concern for human consumption and emphasizes the importance of understanding MP distribution and fate as well as reducing and controlling plastic release into the environment.

In-package cold atmospheric plasma processing for shelf-life extension of gilthead seabream (Sparus aurata) fillets.

In-package cold atmospheric plasma (CAP) processing, which refers to the generation of CAP inside a sealed package, enables a local disinfecting reaction, allowing no post-process contamination and extending the shelf-life (SL) of perishable food products, such as fresh fish. In the present study, four in-package CAP treatments, differing in frequency and processing time, were applied on fresh gilthead seabream (Sparus aurata) fillets, prepacked in low-permeability pouches. Fish SL was evaluated during isothermal storage at 2°C, whereas untreated packaged fillets were used as control samples. The SL assessment of the fish fillets was based on microbial enumeration of total aerobic mesophilic count (TMC), total aerobic psychrotrophic count (TPC), Pseudomonas spp., Enterobacteriaceae, and lactic acid bacteria (LAB), pH measurement, determination of color and texture parameters, lipid oxidation, total volatile basic nitrogen (TVB-N) measurement, and sensory evaluation. All CAP treatments were effective against microbial inhibition in fish fillets, especially regarding TMC, TPC, and Pseudomonas spp., resulting in maximum reduction of 1.49, 1.24, and 1.43logCFU/g, respectively, compared to the control samples after 16 days of storage. However, minor effect was observed against Enterobacteriaceae and no effect against LAB. CAP processing did not affect the color and texture parameters of fish fillets, and TVB-N production was slightly reduced in CAP-treated samples; however, lipid oxidation was accelerated, especially at the more intense processing conditions, by a maximum of 75.5%. The results of the study indicated that in-package CAP processing could be effectively applied for inhibiting spoilage during refrigerated storage and extending SL of fresh fish fillets. PRACTICAL APPLICATION: In-package cold atmospheric plasma (CAP) processing was tested on gilthead seabream fillets, a highly perishable product with high commercial potential if its shelf-life can be extended through minimal processing. The food industry could benefit from in-package CAP technology as it is a cost effective nonthermal processing method while preventing post-processing contamination of the products. Although in-package CAP processing has not been extensively tested on fish, this study examined the quality and shelf-life of a highly perishable fish species, and the results could be further used as a reference for processing optimization of the CAP treatments.

Strategy combining mammalian fats with supplementation of pungent spices in aquafeeds, to mitigate negative impacts of fish oil replacement in fish performance, fillet quality and hepatic condition of gilthead seabream (Sparus aurata)

The replacement of fish oil (FO) in aquafeeds usually leads to imbalances in the dietary content of n-3 and n-6 polyunsaturated fatty acids (PUFA), with negative consequences for fish performance, health, and fillet quality. Animal-rendered fats are an alternative lipid source high in saturated fatty acids, potentially sparing n-3 PUFA from oxidation, and with lower n-6 PUFA contents than plant-based oils, especially in the case of mammalian fats (MF). Hence, this work assessed the effect of replacing 45% FO by MF (negative control, NC) compared to a diet containing only FO (positive control, PC) in gilthead seabream (Sparus aurata, initial body weight: 85 ± 4 g, mean ± standard deviation) at low water temperature. In addition, we studied the effect of supplementing the NC diet with a combination of pungent spices with hypolipidemic and anti-inflammatory properties at three inclusion levels: 0.05 (SPICY0.05%), 0.1 (SPICY0.1%), and 0.15% (SPICY0.15%). At the end of the trial (112 days), FO substitution by MF led to poorer fish performance in terms of body weight (BW), specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio (PER). Supplementation of the NC diet with spices numerically improved SGR, FCR and PER at all inclusion levels (non-significantly different from the PC group), being FCR and PER significantly different from the NC group in the SPICY0.1% and SPICY0.15% treatments. A remarkable increase in lipid level was observed in fillets of fish fed the NC diet, but was fully counteracted by spice supplementation, especially in fish fed the SPICY0.15% diet. A lower fat accumulation was also found in the liver of fish fed the SPICY0.1% and SPICY0.15% diets, with respect to the PC and NC groups. The fillets' fatty acid profile mostly reflected the diet composition, but the SPICY0.15% diet modified it in an inverse direction to that observed in the NC, to more closely resemble the profile of fish fed the PC diet. In particular, the SPICY0.15% diet reduced fillet levels of MUFA, linoleic and linolenic acids, and increased n-3 LC-PUFA (including EPA and DHA), compared to the NC. A microarray-based transcriptomic analysis revealed a better hepatic health status, as indicated by different biological processes associated to immunity. Overall, supplementation with the combination of pungent spices at 0.15% enabled the incorporation of alternative lipid sources, such as MF, in aquafeeds without significantly compromising growth and feeding performance, liver health, and quality of the edible product.

Modelling changes in whole body and fillet fatty acid composition of Atlantic salmon with changing levels of dietary omega-3 intake

In this study, a fatty acid dilution model was coupled with a dynamic nutrient demand model to provide an integrated model capable of predicting the whole-body and fillet lipid and fatty acid levels of Atlantic salmon (Salmo salar) following a change in dietary fatty acid profile. Based on knowledge of the initial fish and dietary fatty acid compositions, diet digestible energy density, the water temperature and duration of feeding, the model demonstrated that it was possible to predict a range of parameters, including the growth, feed utilisation, whole-body and fillet (Norwegian Quality Cut; NQC) total lipid, and fatty acid levels of the fish. The model was validated against five separate experiments, including two farm-based trials with harvest size fish. Validation experiments involved fish ranging in size (initial weights to final weights) from 138 g/fish to 5138 g/fish and running for durations of between 66 and 323 days. For the laboratory experiments, prediction of growth, feed utilisation and fatty acid deposition proved to be highly predictable (R2 > 0.998). Fatty acid profiles from both short and long-term cage trials were also highly predictable. Despite the reduced level of weight change in the short-term cage trial, and the higher variability that was observed in growth performance, the fatty acid deposition still showed high levels of correlation (R2 > 0.996), between the modelled and measured fatty acid levels in the fish fillet. Departure from linearity was more evident in the long-term cage trial, but correlation still exceeded R2 > 0.995 for all treatments. Prediction of whole-body and NQC total lipid levels was less accurate, with correlations being R2 = 0.962 and R2 = 0.909 respectively. Model outputs were generally more accurate with greater weight change and/or experiment duration. The outcome of this study shows that the model developed here provides a useful tool for the estimation of the fatty acid composition of Atlantic salmon following a change in dietary fatty acid composition. This could help assist in the more judicious use of dietary long-chain omega-3 fatty acids for commercial salmon farming.

Effect of Replacing Fishmeal with Algal Meal on Growth Parameters and Meat Composition in Rainbow Trout (Oncorhynchus mykiss W.)

Aquafarms should reduce the use of fishmeal and fish oil in nutritional feed. One such accessible and relatively inexpensive food component that could successfully meet the challenge posed by aquaculture is algae. The objective of the present study was to evaluate the algae meal inclusion of Chlorella and Spirulina sp. in a diet for rainbow trout, evaluating its effects on fish growth, histological parameters and fillet quality. Experiments were carried out to replace 50% and 100% of fishmeal with Spirulina sp. and Chlorella vulgaris in feed for rainbow trout (Oncorhynchus mykiss W.) cultured in a recirculation system. At the end of the experimental period, the highest mean live weight was measured in rainbow trout fed a feed containing 50% algal meal in the feed. The absorptive vacuolization of cells was increased the most and lamina propria was average thickened when fed 50% algae diets. Fat droplets in the hepatocytes were larger in the 50% algae meal fed group, and their nuclei were replaced in the peripheral zone of the cells. Substitution of fishmeal with 50% algal meal in fish feed resulted in a 36.44% reduction in the lipid content of rainbow trout fillets compared to control fish.

Fish Welfare – A Case Study: Reviling for the first-time side effects of vaccination in European sea bass (Dicentrarchus labrax) and barramundi (Lates calcarifer) in the Israeli fish farming

Vaccination is an effective way to control many infectious diseases in fish. Israeli fish farming has successfully used two vaccines over the last 30 years and has no problem with the side effects of vaccination. However, after introducing new species, a new problem emerged: these fish, after vaccination, demonstrated peritoneal lesions such as granulomas. At the same time, the fish did not show retarded growth or suffering during the fattening period. This study was conducted to establish the connection between vaccination and the appearance of granulomas. Evidence drawn from this research work and comparing vaccinated and non-vaccinated fish confirms that intraperitoneal granulomas do not impact the growth, performance, or fish fillet quality at harvest.

Fast and sustainable production of smart nanofiber mats by solution blow spinning for food quality monitoring: Potential of polycaprolactone and agri-food residue-derived anthocyanins

The shelf life of perishable foods is estimated through expensive and imprecise analyses that do not account for improper storage. Smart packaging, obtained by agile manufacturing of nanofibers functionalized with natural pigments from agri-food residues, presents promising potential for real-time food quality monitoring. This study employed the solution blow spinning (SBS) technique for the rapid production of smart nanofiber mats based on polycaprolactone (PCL), incorporating extracts of agricultural residues rich in anthocyanins from eggplant (EE) or purple cabbage (CE) for monitoring food quality. The addition of EE or CE to the PCL matrix increased the viscosity of the solution and the diameter of the nanofibers from 156 nm to 261–370 nm. The addition of extracts also improved the mechanical and water-related properties of the nanofibers, although it reduced the thermal stability. Attenuated total reflectance Fourier-transform infrared spectroscopy confirmed the incorporation of anthocyanins into PCL nanofibers. Nanofiber mats incorporated with EE or CE exhibited visible color changes (ΔE ≥ 3) in response to buffer solutions (pH between 3 and 10), and ammonia vapor. Smart nanofibers have demonstrated the ability to monitor fish fillet spoilage through visible color changes (ΔE ≥ 3) during storage. Consequently, smart nanofibers produced by the SBS technique, using PCL and anthocyanins from agro-industrial waste, reveal potential as smart packaging materials for food.

Mechanisms underlying the potent antimicrobial effects of plasma-activated seawater (PASW) on fish spoilage bacterium Shewanella putrefaciens

Plasma-activated seawater (PASW) presents a promising approach for marine fish preservation, yet its antimicrobial efficacy and mechanisms remain unclear. This study found that PASW exhibits superior bactericidal properties against the fish spoilage bacterium Shewanella putrefaciens compared to plasma-activated water (PAW), and increased effectiveness in preserving fish fillets. To clarify the mechanisms, a detailed investigation was conducted, including the generation of reactive oxygen/nitrogen species (ROS/RNS) and active halogen species in PASW, and their antimicrobial efficacy. Findings showed greater nitrite and hydrogen peroxide production in PASW relative to PAW, as well as the conversion of chloride/bromide ions into active species, which collectively enhanced PASW's antimicrobial activity. The synergistic action of ROS/RNS and active chlorine/bromine species in PASW promoted the generation of intracellular ROS, causing increased membrane damage, redox imbalance, and consequently higher bacterial mortality. This study enhances our understanding of PASW's antimicrobial effects and highlights its potential applications in the seafood industry.

Indicator Films Containing Dendrobium Orchid Flower Extract and TiO2 Nanoparticles for Monitoring Fish Fillet Spoilage

This work aimed to study a novel pH indicator film prepared from carboxymethyl cellulose (CMC)/tapioca starch (TS) incorporating Dendrobium orchid flowers and TiO2 nanoparticles for monitoring fish fillet freshness. The films were prepared based on carboxymethyl cellulose (CMC) and tapioca starch (TS) blend (CMC/TS) incorporated with TiO2 nanoparticles and Dendrobium orchid flower (DOF) extract. The result showed that the DOF extract contained peonidin-3,5-O-diglucoside and exhibited distinguishable color changes in different pH buffers. Likewise, the CMC/TS+TiO2+DOF film’s color changed corresponding to the extract. The X-ray diffraction analysis revealed the expansion of the film’s amorphous region, due to the intermolecular interactions. Analyzing scanning electron microscope images showed the effects of TiO2 and DOF extract on the surface morphology of films. The incorporation of TiO2 and DOF extract into the film formulation improved various film properties, such as redness, opacity, tensile strength, and water solubility. For the sensitivity testing, the color of the CMC/TS+TiO2+DOF film responded to ammonia vapor more than acetic acid vapor, suitable for monitoring seafood spoilage behavior. In addition, the application of film for monitoring the freshness of fish fillets was conducted. The CMC/TS+TiO2+DOF film color changed from purple to bluish-purple corresponding to the spoilage of samples. Indicating its potential as an indicator for monitoring fish fillets' freshness.

Effects of packaging method and temperature on the quality and lipid degradation of snakehead fish (Channa striata) fillets during frozen storage

Temperature and packaging method are considered the main factors affecting the quality of fishery products during frozen storage. In the present study, snakehead fish fillets were air (AP) and vacuum (VP) packaged and stored at -20±2°C and -25±2°C for six months to investigate the effects of temperature and packaging method on the quality of snakehead fish fillets. Changes in the quality of snakehead fish fillets were assessed by determinations of lipid hydrolysis, lipid oxidation, and their resulting changes in colour, cooking yield (CY), and total volatile basic nitrogen (TVB-N) content. Storage temperature and packaging method showed strong preservative effects on the quality of snakehead fish fillets. Higher cooking yield and lower TVB-N content were observed in the VP samples stored at -25±2°C compared to the AP samples and stored at -20±2°C. Vacuum packaging and lower storage temperature (i.e. -25±2°C) significantly retarded lipid hydrolysis and lipid oxidation development. This resulted in lower free fatty acid (FFA), lipid hydroperoxides (PV), thiobarbituric acid-reactive substances (TBARS) values, and higher phospholipid content. Significant correlations between lipid oxidation products (PV and TBARS) and yellow discolouration (b* values) were found in this study. Based on these findings, it could be suggested that frozen snakehead fish fillets should be vacuum-packaged and stored at low temperatures to maintain their quality.

Clove essential oil decreases antemortem stress and acts as an antioxidant in Nile tilapia

ABSTRACT This study investigated the effect of clove essential oil used prior to stunning by cranial percussion and hypothermia on Nile tilapia (Oreochromis niloticus) welfare and fillet quality. A total of 100 tilapias were divided into four groups in a 2 × 2 factorial design, exploring two stunning methods with and without clove essential oil. Behavioral responses, glucose, lactate, pH, water holding capacity, color parameters, lipid and protein oxidation, and oxidative stress were analyzed. The application of clove essential oil resulted in 100% numbing in swimming and stimulus response behaviors, and 96% in balance and eye vestibule reflex variables. Significant reductions in glucose (12.12 mg dL−1) for hypothermia group (p = 0.001) and lactate (3.36 mmol L−1) for cranial percussion (p = 0.004), 0.028 nmol lipid oxidation in hypothermia treatment (p = 0.009), and 0.134 nmol carbonyls/mg protein (p = 0.001) were observed. There was a reduction in luminosity (p = 0.010) and red intensity (p = 0.001) in the group of fish fillet that received cranial percussion, however, there was no difference in the group stunned by hypothermia. Clove essential oil demonstrates effectiveness in pre-slaughter stress mitigation, influencing the antioxidant system positively. Its usage in pre-slaughter protocols could contribute to improved fillet quality, presenting a promising alternative for enhancing tilapia welfare during slaughter.

A challenge test on Pseudomonas spp. as spoiling microorganism in fish fillets

Fish fillets are highly susceptible to spoilage, with Pseudomonas spp. bacteria being among the main culprits. To maintain products’ quality and safety, it is important to control the load of these microorganisms and understand their growth potential in fish fillets. However, setting up challenge tests might be hard due to the difficulty of differentiating intentionally inoculated bacteria from those already present on the fillets. To overcome this obstacle, a pilot study using Pseudomonas aeruginosa, a clinically significant bacterial species that is rare in food, was conducted. Vacuum-packed Northern cod, salmon, and plaice fish fillets were experimentally inoculated and subjected to trials at both refrigeration (4 °C) and thermal abuse temperatures (from +4 °C to +6 °C and then to +8 °C). The results showed that the growth potential of Pseudomonas aeruginosa in all the fish fillets was less than 0.5 Log10 CFU/g. This confirms that vacuum packaging could reduce the multiplication of Pseudomonas spp. in the fish fillets and underlines as it is crucial to have fish fillets containing initial loads of Pseudomonas between 104-105 CFU/g or lower at the beginning of the shelf life in order to control the deterioration rate of the product. This study provides a basis for developing further challenge tests for Pseudomonas spp. in the fish industry and highlights the importance of controlling initial loads of Pseudomonas to prevent product deterioration during the shelf life.

The Effect of Sumac (Rhus coriaria L.) Application on Oxidation Status, Sensory Attributes, Physicochemical and Microbiological Parameters of Carp (Cyprinus carpio) Fish during Chilled Storage

The aim of this study was to evaluate the impact of sumac on the oxidation status, sensory properties, and physicochemical and microbiological parameters of common carp (Cyprinus carpio) fish during chilled storage. Fillets of carp were treated with ground sumac at percentages of 0% (T0), 0.5% (T1), 1.5% (T2) and 2.5% (T3) and analysed after 24 and 72 h of chilled storage. The fat content, oxidation parameters (thiobarbituric acid reactive substances, TBARS), antioxidant capacity, total volatile basic nitrogen (TVB-N), free fatty acids (FFA), sensory properties, colour indicators (lightness L*, redness a*, yellowness b*), water activity, pH value, aerobic plate count (APC), psychrotrophic microorganism count (PMC), and coliform bacteria count were determined. The TBARS values of T1, T2, and T3 decreased significantly (p < 0.05) after 24 h of chilled storage. The antioxidant capacity increased in a dose-dependent and time-dependent manner. As regards organoleptic properties, sumac was able to reduce the natural fishy odour, increase the sour odour and flavour, and mask the fish odour and flavour significantly. A significant effect of sumac on the redness (a*) values of muscles was observed, which increased with elevation of the sumac ratio. A decrease in fillet pH and lower APC and PMC were observed. No effect was found on water activity or the growth of coliform bacteria. The study found that sumac plays a role in the oxidation status, pH value and organoleptic properties of fish fillets, which could be beneficial for the fish and fishery products industry.

DNA Barcoding Revealed a High Percentage of Mislabeling in Commercial Fish Products: The First Empirical Survey in South Texas

Seafood mislabeling is a widespread problem that have produced a growing distrust of seafood industry. In this study, we examined the prevalence of mislabeling in fish samples from regional markets in the greater Houston area and close-by coastal communities. A total of 63 fish fillet samples were purchased, labeled, and stored at -20˚C in individual packages until DNA extraction. DNA fragments of roughly 700 base pairs encoding cytochrome oxidase I (COI) were PCR-amplified from each DNA sample. With 99.6–100% nucleotide identity in the GenBank and BOLD databases, all samples were correctly identified at the species level. The scientific names identified by DNA barcoding were matched with legally acceptable market names using the US Food and Drug Administration (FDA) Seafood List. Out of the 63 samples examined, 13 samples (20.6%) were mislabeled. Moreover, 24 samples (38.1%) did not use the acceptable market names, indicating that the FDA policy is poorly implemented in seafood industry. The first DNA barcoding survey this area warranted the need of continuous monitoring and the dissemination of the regulation combined with taxonomic knowledge.

Effects of different freezing methods on muscle qualities and myofibrillar protein properties of red drum (Sciaenops ocellatus) during storage

The freezing of aquatic products without causing significant changes in quality is recently attracting much attention. In this study, the effects of air freezing (AF, -20 °C), blast freezing (BF, -35 °C), liquid nitrogen freezing (LNF), and immersion freezing (IF, -35 °C) by 20 % ethanol, 20 % propylene glycol, 10 % glycerol, and 10 % sodium chloride aqueous solutions, respectively, on muscle qualities and myofibrillar protein properties of the red drum were investigated. The results indicated that the freezing rate of IF was 2.66 cm/h, which was 6.33 times higher than that in AF groups. Compared with AF and BF, the ice crystals were smaller and more uniformly shaped, with properties of lower water migration and less texture softening after cryogenic liquid freezing of IF and LNF group aquatic products. Immersion freezing showed the same superiority in maintaining the freshness of fish fillets and retaining the protein structure as liquid nitrogen storage. Overall, IF has similar effects to LNF in maintaining muscle qualities and myofibrillar protein properties. This study describes a new freezing method that uses 20 % ethanol, 20 % propylene glycol, 10 % glycerol, and 10 % sodium chloride aqueous solutions as immersion freezing medium. The multi-compound freezing medium has the potential to be used for the freezing of aquatic products.

Differentiation between fresh and frozen-thawed mackerel fish using low-cost portable near infrared spectrometry devices

Mislabelling frozen-thawed fish fillets as fresh is one of the most important fraudulent practices during commercialisation. This study aimed to determine the ability of two portable miniaturised low-cost near-infrared spectroscopy (NIR) devices intended for consumers to discriminate between fresh and thawed mackerel (submitted to one or two frozen-thawed cycles) and between different freezing systems. The effect of different fish seasonal characteristics on the performance of the model was also evaluated. The low-cost NIR devices were able to discriminate between fresh and thawed samples with a classification rate of 90.3% and 94.1% and the freezing system to which they were submitted with a classification rate of 91.2% and 89.7%. These findings suggest that low-cost portable NIR spectroscopy can be a valuable tool for detecting mislabeled frozen-thawed products sold as fresh, providing consumers with a rapid and affordable method for fraud detection.

Effects of packaging methods and temperature variations on the quality and microbial diversity of grouper (Epinephelus Lanceolatus) during cold storage

Microbial growth and its metabolism are the primary reasons for fish spoilage. In this study, the effects of temperature fluctuations and modified atmosphere packaging (MAP) on the quality and microbial diversity of grouper (Epinephelus lanceolatus) during cold storage were investigated. Fish fillets were packed in air packaging (AP), vacuum packaging (VP), MAP1 (40% CO2/55% N2/5% O2), and MAP2 (60% CO2/35% N2/5% O2), and stored at T1 (4 °C) and T2 (4–8 °C temperature fluctuations), respectively. Total viable counts (TVC), psychrophilic bacteria count, Pseudomonas count, and H2S-producing bacteria count all increased during cold storage. Pseudomonas, Serratia, and Carnobacterium were the dominant genera in AP, VP, and MAP2 at T1 storage, with relative abundances of 82.7%, 54.5%, and 57.3%, respectively. Temperature fluctuations accelerated the spoilage process of the grouper, and increased the relative abundance of Serratia in the samples, but had less effect on the composition of these spoilage bacterial members. The microbial community was more affected by the different gas atmospheres. MAP inhibited the growth of Pseudomonas and increased the relative abundance of Carnobacterium and Psychrobacter in the samples. Low temperature and MAP effectively suppressed the rise of pH, total volatile basic nitrogen (TVB-N), trimethylamine (TMA), thiobarbituric acid reactive substances (TBARs), and K values and maintained the water holding capacity (WHC) and sensory quality of the samples. Grouper had the longest shelf life under MAP2-T1 treatment. The MAP2-T1 samples maintained lower levels of TVB-N (151.8 mg/kg), TMA (7.6 mg/kg), TBARs (0.90 mg MDA/kg), and K value (48.5%) and higher levels of WHC (77.6%) on the 18th day, with a lower degree of spoilage compared to other samples.