Ciguatoxin Detection in Flesh and Liver of Relevant Fish Species from the Canary Islands

The Canary Islands are a ciguatoxin (CTX) hotspot with an established official monitoring for the detection of CTX in fish flesh from the authorised points of first sale. Fish caught by recreational fishermen are not officially tested and the consumption of toxic viscera or flesh could lead to ciguatera poisoning (CP). The objectives of this study were to determine the presence of CTX-like toxicity in relevant species from this archipelago, compare CTX levels in liver and flesh and examine possible factors involved in their toxicity. Sixty amberjack (Seriola spp.), 27 dusky grouper (Epinephelus marginatus), 11 black moray eels (Muraena helena) and 11 common two-banded seabream (Diplodus vulgaris) were analysed by cell-based assay (CBA) and Caribbean ciguatoxin-1 (C-CTX1) was detected by liquid chromatography mass spectrometry (LC-MS/MS) in all these species. Most of the liver displayed higher CTX levels than flesh and even individuals without detectable CTX in flesh exhibited hepatic toxicity. Black moray eels stand out for the large difference between CTX concentration in both tissues. None of the specimens with non-toxic liver showed toxicity in flesh. This is the first evidence of the presence of C-CTX1 in the common two-banded seabream and the first report of toxicity comparison between liver and muscle from relevant fish species captured in the Canary Islands.

Development of a Quality Index Method Scheme for Sensory Assessment of Chilled Yellowfin Tuna

Background: Quality monitoring and/or assessment are parts of a freshness/quality control system, which is of utmost importance for fresh seafood, especially Scombridae fish. The quality index method (QIM) is a simple, convenient, unique, and reliable tool to determine the sensory status and estimate the remaining shelf life of aqua products. Objective: This study aimed to develop a QIM scheme for chilled stored yellowfin tuna and apply the protocol in the fish quality evaluation and storage time estimation. Method: Eight gutted yellowfin tuna of 20, 30, and 40 kg up were used in the study. Five panelists participated in the QIM development, training and application. Control and/or validation analyses were sensory assessment by a control sheet, total volatile basic nitrogen (TVB-N) quantification, and total viable count (TVC) determination. Chilled storage of tuna was performed in liquid ice and traditional crushed block ice. Partial least square regression (PLS-R) was conducted on quality index (QI) dataset over storage time to find the regression line and prediction accuracy. Results: The established QIM protocol for gutted yellowfin tuna comprised 6 attributes (namely, color of whole fish, odor of whole fish and flesh, eyes, appearance of whole fish, flesh color and flesh texture) and a maximal QI of 15. The PLS-R showed that QI could be used to estimate the remaining time with a precision of ± 2.0 and 1.4 days for fish stored in slurry ice and crushed ice, respectively. The TVB-N content in the fish flesh maintained below the acceptable level of 25 mg N/100 g throughout the storage period, which made the parameter impractical to detect the fish shelf life. The TVC overreached the allowable level of 107 CFU/g around the time of fish rejection by the sensory method. Conclusion: The developed QIM scheme for yellowfin tuna showed to be more advantageous in detecting fish quality changes compared to the control sensory method and could be used to estimate the fish's remaining shelf life.

Mesopelagic flesh shear viscosity estimation from in situ broadband backscattering measurements by a viscous–elastic model inversion

In fisheries acoustics, target strength (TS) is a key parameter in converting acoustic measurements to biological information such as biomass. Modelling is a versatile tool to estimate TS of marine organisms. For swimbladdered fish, flesh shear viscosity is one of the required parameters to correctly calculate TS around the resonance frequency, where the target scatters most strongly. Resonance of mesopelagic swimbladdered fish can occur over a range of frequencies and can be within commonly used frequencies (e.g. 18, 38, or 70 kHz). Since there is little information on flesh shear viscosity of fish, especially for mesopelagic species, their resonance can bias the biological information extracted from acoustic measurements. Here, first, the applicability of using a spherical model to estimate resonant backscattering of a generic swimbladder is investigated. Subsequently, a viscous–elastic spherical gas backscattering model is used to estimate the flesh shear viscosity of swimbladdered mesopelagic fish (most likely Cyclothone spp., Family: Gonostomatidae) from in situ broadband backscattering measurements. Finally, the effects of flesh shear viscosity on the TS of swimbladdered mesopelagic fish at 18, 38 (a widely used channel to study mesopelagic layers), and 70 kHz are examined.

The Effect of Using Bromelain and Papain Enzymes on the Quality of Pure Fish Oil from Milkfish Silage (Chanos chanos)

Highlight ResearchMilkfish silage oil fatty acid profileThe quality of pure fish oil from milkfish silage (Chanos chanos)The effect of using bromelain and papain enzymesAbstractMilkfish has a high nutritional content, especially fat content. The processing of milkfish oil into pure oil has not been done much. Proper processing is needed so that the fatty acids contained in fish can be utilized optimally for pharmaceutical and medical needs. Enzyme extraction is known to extract fish oil with better quality than the heating method. The aim of this research was to study the effect of the enzymes bromelain and papain on the quality of pure fish oil from milkfish silage by treating different body parts used. The experiment was carried out with Factorial Complete Randomized Design with three replications involving two factors. The first factor was the type of enzyme using two types of enzymes, namely bromelain and papain with a concentration of 15%, the second factor used was the difference in body parts that was whole fish, flesh, and waste (head, viscera, and bones). The results showed that the type of enzyme had no significant effect on the quality of fish oil, but the different treatments of fish body parts had a significant effect on the quality of the fish oil produced. The best treatment was adapted from fish oil treated using the bromelain enzyme with the flesh. This treatment resulted in yield of 1.25%, density 0.903 g/mL, FFA content of 0.56%, and peroxide value of 7.64 meq/kg.

Fatty Acid Composition and Cholesterol Content of Some Economic Marine Fish in Turkish Waters

The basic concept of balanced and healthy nutrition depends on the consumption of right foods at the right amounts. The nutrient of foods is affected by variable factors such as geographical and ecological characteristics, harvest time, processing and transportation, storage, and consumption conditions. High qualified instrumental analyses techniques should be done while the determination of the nutrient levels. Because, the quality of results of the analysis are the most important criterion in creating food composition tables, the database and data sets. In this study, the basic nutrient composition of some economic marine fish was determined. For this, fish were collected from the Black Sea and the Marmara Sea was composites formed from the fish flesh separately for each region. Then, moisture, ash, fat, protein, fatty acids composition, and cholesterol levels were examined with the composites. While the average values were obtained according to the results of the analysis, differences among regions were examined. While the fat content in anchovy, bluefish, bonito, and barbatus is above %10 g/100g, in whiting was approximate %1. Average EPA and DHA values in anchovy are %15,86 and %17,01 respectively. The highest cholesterol was obtained in whiting as around 77 mg/100g.

Efficient water treatment achieved in recirculating aquaculture system using woodchip denitrification and slow sand filtration

For a recirculating aquaculture system (RAS), a passive water treatment system was designed for efficient discharge nutrient removal and water reuse in RAS production. Denitrification in a woodchip bioreactor filled with birch wood (Betula pendula) followed by sand filtration was introduced into a side-loop of an experimental RAS rearing rainbow trout (Oncorhynchus mykiss). Denitrification efficiency remained high (96%) throughout the experiment and reached a nitrogen removal rate of 15 g NO3-N m−3 per day. Sand filtration was used to remove dissolved and particulate matter and improve water quality before being returned to water circulation. To ensure the absence of harmful substances in the system, heavy metals were quantified. Additionally, off-flavor-inducing compounds were quantified in the circulating water and in fish flesh. Significantly higher concentrations of geosmin (GSM) (p<0.05) were observed in the controls compared to side-looped systems, but a similar effect was not observed in the case of 2-methylisoborneol (MIB). Among heavy metals, concentrations of Co (30 μg L−1), Ni (40 μg L−1), and Pb (140 μg L−1) decreased to below 10 μg L−1 in the side-loop water after the start-up of the system. Only low concentrations of Cu (5–30 μg L−1) were found in the rearing tank water, in both the side-loop and controls. The results indicated that this type of process design is suitable for safely producing fish of high quality.

Use of aromatic root vegetables in the technology of freshwater fish preserves

The expediency of using freshwater fish and aromatic root vegetables in the technology of preserves has been substantiated. Based on the organoleptic analysis, the compatibility of freshwater fish and aromatic vegetables as part of preserves has been determined. The conditions for pretreatment of salted semi-finished products to ensure their maturation as part of preserves have been theoretically substantiated and experimentally determined. It has been found that pretreatment of freshwater fish flesh with 1.0% and 1.5% malic acid for 60 minutes provides soft, tender and juicy consistency, which corresponds to an organoleptic rating of 5 points. Changes in the fatty acid composition of preserves are mainly associated with an increase in the amount of polyunsaturated fatty acids that have been introduced with linseed oil, which is a positive factor. It has been found that, in comparison with the control sample, the level of all mineral elements in preserves with aromatic root vegetables is significantly increased, with fiber present, which indicates the expediency of introducing aromatic root vegetables into this product to enrich it with essential mineral and carbohydrate elements to obtain a high-value and healthy food product. Enriching the formulation of preserves made of freshwater fish with a variety of herbal additives increases their nutritional value and allows to get a product of high value enriched with such vital nutrients as carbohydrates, calcium, potassium, phosphorus, sulfur, sodium, magnesium, manganese, and iron. Aromatic root vegetables such as horseradish, parsley, and ginger have been found to exhibit antiseptic properties and delay the activity of microbial enzymes as they content phenol. Therefore, the use of aromatic root vegetables helps to inhibit the oxidation and hydrolysis of fats, which may be due to the presence of phenols in their composition.

Characteristic Distribution of Ciguatoxins in the Edible Parts of a Grouper, Variola louti

Ciguatera fish poisoning (CFP) is one of the most frequently encountered seafood poisoning syndromes; it is caused by the consumption of marine finfish contaminated with ciguatoxins (CTXs). The majority of CFP cases result from eating fish flesh, but a traditional belief exists among people that the head and viscera are more toxic and should be avoided. Unlike the viscera, scientific data to support the legendary high toxicity of the head is scarce. We prepared tissue samples from the fillet, head, and eyes taken from five yellow-edged lyretail (Variola louti) individuals sourced from Okinawa, Japan, and analyzed the CTXs by LC-MS/MS. Three CTXs, namely, CTX1B, 52-epi-54-deoxyCTX1B, and 54-deoxyCTX1B, were confirmed in similar proportions. The toxins were distributed nearly evenly in the flesh, prepared separately from the fillet and head. Within the same individual specimen, the flesh in the fillet and the flesh from the head, tested separately, had the same level and composition of toxins. We, therefore, conclude that flesh samples for LC-MS/MS analysis can be taken from any part of the body. However, the tissue surrounding the eyeball displayed CTX levels two to four times higher than those of the flesh. The present study is the first to provide scientific data demonstrating the high toxicity of the eyes.