Use of Ultrasound to Determine Cod Fillet Composition

The relationships between the composition and ultrasonic properties of Atlantic cod (Gadus morhua) fillets were examined. The lipid, protein, moisture and ash contents of cod fillets were determined by official methods. The ultrasonic velocity and attenuation coefficient of the fillets were measured using a pulse-echo technique. The ultrasonic velocity of the fillets varied between 1575 and 1595 m s^?1, decreasing linearly with increasing moisture content (r² > 0.8 for 26 samples). No systematic relationship was observed between the attenuation coefficient and moisture content. Our experiments highlight the potential of using ultrasonic velocity measurements to rapidly and nondestructively determine the moisture content of cod fillets (and possibly their protein content by deduction).     

Liquid holding capacity,texture and fatty acid profile of smoked fillets of Atlantic salmon fed diets containing fish oil or soybean oil

This study evaluates the effects of dietary vegetable oils on the liquid-holding capacity, texture properties and fatty acid composition of Atlantic salmon fillets. Three diets containing 100% of fish oil (FO), 100% of soybean oil (SO) or a 50/50 mixture of the two oils (FO/SO) as oil dietary source, were fed to triplicate groups of salmon. After slaughter, a third of the fish were studied fresh while the rest of fish were smoked and stored at two temperatures (4 °C or 14 °C) for 5 or 15 days. The liquid-holding capacity and the texture of fresh and smoked fillets were not significantly affected by dietary oil whereas the smoking yield increased with the inclusion of soybean oil. The fatty acid profile of fresh and smoked fillets reflected these of the diets, and no selective loss of fatty acids was observed after smoking and after storage. On the other hand, increased storage time and storage temperature reduced strongly the liquid-holding capacity of all smoked salmon particularly obvious as increased fat loss, irrespective of the diets. This study showed that an increase in storage time and temperature of smoked fillets of Atlantic salmon affected the liquid-holding capacity, irrespective of the diets.     

Levels of synthetic antioxidants (ethoxyquin, butylated hydroxytoluene and butylated hydroxyanisole) in fish feed and commercially farmed fish

Several synthetic antioxidants are authorized for use as feed additives in the European Union. Ethoxyquin (EQ) and butylated hydroxytoluene (BHT) are generally added to fish meal and fish oil, respectively, to limit lipid oxidation. The study was conducted to examine the concentrations of EQ, BHT and butylated hydroxyanisole (BHA) in several commercially important species of farmed fish, namely Atlantic salmon, halibut and cod and rainbow trout, as well as concentrations in fish feed. The highest levels of BHT, EQ and BHA were found in farmed Atlantic salmon fillets, and were 7.60, 0.17 and 0.07 mg kg(-1), respectively. The lowest concentrations of the synthetic antioxidants found were in cod. The concentration of the oxidation product ethoxyquin dimer (EQDM) was more than ten-fold higher than the concentration of parent EQ in Atlantic salmon halibut and rainbow trout, whereas this dimer was not detected in cod fillets. The theoretical consumer exposure to the synthetic antioxidants EQ, BHA and BHT from the consumption of farmed fish was calculated. The contribution of EQ from a single portion (300 g) of skinned fillets of the different species of farmed fish would contribute at most 15% of the acceptable daily intake (ADI) for a 60 kg adult. The consumption of farmed fish would not contribute measurably to the intake of BHA; however, a 300 g portion of farmed Atlantic salmon would contribute up to 75% of the ADI for BHT.     

Levels of synthetic antioxidants (ethoxyquin,butylated hydroxytoluene and butylated hydroxyanisole) in fish feed and commercially farmed fish

Several synthetic antioxidants are authorized for use as feed additives in the European Union. Ethoxyquin (EQ) and butylated hydroxytoluene (BHT) are generally added to fish meal and fish oil, respectively, to limit lipid oxidation. The study was conducted to examine the concentrations of EQ, BHT and butylated hydroxyanisole (BHA) in several commercially important species of farmed fish, namely Atlantic salmon, halibut and cod and rainbow trout, as well as concentrations in fish feed. The highest levels of BHT, EQ and BHA were found in farmed Atlantic salmon fillets, and were 7.60, 0.17 and 0.07?mg?kg^?1, respectively. The lowest concentrations of the synthetic antioxidants found were in cod. The concentration of the oxidation product ethoxyquin dimer (EQDM) was more than ten-fold higher than the concentration of parent EQ in Atlantic salmon halibut and rainbow trout, whereas this dimer was not detected in cod fillets. The theoretical consumer exposure to the synthetic antioxidants EQ, BHA and BHT from the consumption of farmed fish was calculated. The contribution of EQ from a single portion (300?g) of skinned fillets of the different species of farmed fish would contribute at most 15% of the acceptable daily intake (ADI) for a 60?kg adult. The consumption of farmed fish would not contribute measurably to the intake of BHA; however, a 300?g portion of farmed Atlantic salmon would contribute up to 75% of the ADI for BHT.     

Low detection efficiency of candling as a commonly recommended inspection method for nematode larvae in the flesh of pelagic fish

The third-stage larvae of the parasitic nematode Anisakis simplex commonly occur in most commercially important fish species from the North Atlantic. In this study, the occurrence and site distribution of Anisakis larvae in various size groups of Norwegian spring spawning herring (Clupea harengus), blue whiting (Micromesistius poutassou), and mackerel (Scomber scombrus) from the Northeast Atlantic was investigated. Although most of the larvae were found in the abdominal cavity, the small proportion lodged in the flesh was sufficient to affect food quality and safety. However, the prevalence of Anisakis larvae in fish fillets varied considerably among the size groups of each species: 15 to 60% in herring, 32 to 77% in mackerel, and 89 to 100% in blue whiting. The commonly recommended nematode detection method in the fish processing industry is candling, i.e., a brief visual inspection on a light table. Comparison of successively more accurate detection methods, i.e., candling, enzymatic degradation, and UV illumination, for fillets of each fish species revealed that only 7 to 10% of the nematode larvae present in the fillets were detected by candling. The candling efficiency was apparently independent of fillet thickness. Thus, candling is not sufficient to detect the majority of the nematodes that are actually present in the fillets of pelagic fish from the Northeast Atlantic. These findings emphasize the importance of adequate deep-freezing of any fresh pelagic fish product, especially if it is intended for consumption in a raw or semiraw state.     

CHEMICAL COMPOSITION AND POSTMORTEM CHANGES IN SOFT TEXTURED MUSCLE FROM INTENSELY FEEDING ATLANTIC COD (GADIUS MORHUA, L)

Soft textured fillets from postspawning Atlantic cod caught during the influx of capelin exhibited significantly more drip than fillets from fish caught at other times of the 1983 inshore fishing season. The extent and rate of pH decline, protein, collagen and temperature of the muscle were not distinctive in fish caught during the influx of capelin. The muscle from these fish were unique in exhibiting a rapid and relatively low ultimate pH together with a stable pH after the onset of rigor mortis. The number of capelin present in the stomach of cod at the time of catch was positively related (r = 0.92) to the amount of free drip recovered from the fillets.     

Effects of different salting and smoking processes on the microstructure, the texture and yield of Atlantic salmon (Salmo salar) fillets

The effect of different conditions during the salting and smoking process on the microstructure and the texture of salmon fillets was studied in interaction with different raw salmon material; ocean-ranched Atlantic salmon (Salmo salar) from Iceland and two groups of farmed Atlantic salmon (Salmo salar) from Norway, one from Northern Norway and one from Western Norway. The ocean-ranched salmon was found to have significantly smaller fiber diameters and higher shear force compared to the farmed fish. The cross-sectional area of the muscle fibers decreased during the salting and smoking process. Small differences were noted in the cross-sectional area between smoked fillets processed by different salting and smoking methods. However, the cross-sectional area of fibers in dry salted fish fillets from the farmed groups were significantly smaller than in the brine salted fillets, as the fibers shrunk more during dry salting than brine salting. The force required to shear the smoked fillets was significantly higher than for the unprocessed fillets, but was not found to be related to the different salting and smoking processes. Yield during smoking was not related to the initial cross-sectional area or the shear force of the unprocessed muscle.     

Atlantic salmon skin and fillet color changes effected by perimortem handling stress, rigor mortis, and ice storage

ABSTRACT:  The changes in skin and fillet color of anesthetized and exhausted Atlantic salmon were determined immediately after killing, during rigor mortis, and after ice storage for 7 d. Skin color (CIE L *, a *, b *, and related values) was determined by a Minolta Chroma Meter. Roche Salmo Fan™ Lineal and Roche Color Card values were determined by a computer vision method and a sensory panel. Before color assessment, the stress levels of the 2 fish groups were characterized in terms of white muscle parameters (pH, rigor mortis, and core temperature). The results showed that perimortem handling stress initially significantly affected several color parameters of skin and fillets. Significant transient fillet color changes also occurred in the prerigor phase and during the development of rigor mortis. Our results suggested that fillet color was affected by postmortem glycolysis (pH drop, particularly in anesthetized fillets), then by onset and development of rigor mortis. The color change patterns during storage were different for the 2 groups of fish. The computer vision method was considered suitable for automated (online) quality control and grading of salmonid fillets according to color.     

Atlantic salmon (Salmo salar,L) as raw material for the smoking industry. II: Effect of different smoking methods on losses of nutrients and on the oxidation of lipids

The changes in total fat content, fatty acid composition, tocopherol, ascorbic acid, pH and oxidation were analysed in Atlantic salmon (Salmo salar, L.) in response to either cold smoking (20 or 30 °C) or electrostatic smoking. Both fresh and frozen fillets were dry-salted before smoking. The fish smoked were the lean ocean-ranched salmon caught off Iceland in June 1998 and farmed Norwegian salmon, slaughtered in either November 1998 or April 1999, differing in fresh fillet fat content from 84 to 169 g·kg⁻¹ wet weight. The fresh material used in smoking significantly affected the smoking loss of nutritive components in the fillets. The leaner the fish the higher percentile loss in fillet fat. Ascorbic acid decreased about 80 percent from the fresh value, independent of smoking temperature (20 or 30 °C). The fish that were dry-salted and electrostatically smoked only lost about 10 percent of the fresh ascorbic acid content, independent of the type of raw material used, indicating a conserving effect on ascorbic acid by the electrostatic process. Also, the electrostatically smoked fish showed a smaller drop in fillet pH than cold-smoked fillets, while tocopherol was little affected by the smoking methods tested.     

Effects of Added Salt, Phosphates, and Proteins on the Chemical and Physicochemical Characteristics of Frozen Cod (Gadus morhua) Fillets

ABSTRACT: Cod fillets were injected with brine, then immersed in brine with the same composition as used for injection, and finally frozen in a plate freezer. The composition of the brine varied with groups, containing phosphates (3%), salt (5%), and/or proteins (10%), soy protein concentrate, or hydrolyzed cod proteins. The fillets were stored at -24 °C for 3 mo and then thawed to evaluate the effects on yield after thawing and cooking, drip, water-holding capacity, pH, and chemical composition. Addition of proteins slightly increased the yield of thawed fillets, but salt and phosphates were more effective. Comparison of the different proteins showed that fish proteins were not as effective as soy proteins with respect to the physicochemical parameters evaluated with the exception of water-holding capacity. The use of both type of proteins resulted in a negative appearance of the fillets, such as discoloration and slimy surface.     

Ultrasonic characterization of Atlantic mackerel (Scomber scombrus)

The influence of frequency (1–6 MHz), temperature (5–25°C) and composition on the ultrasonic velocity and attenuation coefficient of Atlantic mackerel (Scomber scombrus) was investigated. The ultrasonic velocity was insensitive to frequency, whereas the attenuation coefficient increased with frequency. The fat, water and solids-non-fat content of mackerel tissue was determined by analyzing the temperature dependence of the ultrasonic velocity in the tissue using a semi-empirical equation. There was good agreement between the fat, water and solids-non-fat content determined by ultrasonic velocity and proximate analysis methods. In particular, there was a high correlation between the two methods for the determination of fat content (r²=0.949). There was no correlation between the composition of mackerel tissue determined by ultrasonic attenuation and proximate analysis methods. The increase in ultrasonic attenuation of mackerel with temperature, especially above about 20°C, was attributed to protein denaturation and tissue disruption.     

Computer vision-based evaluation of pre- and postrigor changes in size and shape of Atlantic cod (Gadus morhua) and Atlantic salmon (Salmo salar) fillets during rigor mortis and ice storage: effects of perimortem handling stress

The present study describes the possibilities for using computer vision-based methods for the detection and monitoring of transient 2D and 3D changes in the geometry of a given product. The rigor contractions of unstressed and stressed fillets of Atlantic salmon (Salmo salar) and Atlantic cod (Gadus morhua) were used as a model system. Gradual changes in fillet shape and size (area, length, width, and roundness) were recorded for 7 and 3 d, respectively. Also, changes in fillet area and height (cross-section profiles) were tracked using a laser beam and a 3D digital camera. Another goal was to compare rigor developments of the 2 species of farmed fish, and whether perimortem stress affected the appearance of the fillets. Some significant changes in fillet size and shape were found (length, width, area, roundness, height) between unstressed and stressed fish during the course of rigor mortis as well as after ice storage (postrigor). However, the observed irreversible stress-related changes were small and would hardly mean anything for postrigor fish processors or consumers. The cod were less stressed (as defined by muscle biochemistry) than the salmon after the 2 species had been subjected to similar stress bouts. Consequently, the difference between the rigor courses of unstressed and stressed fish was more extreme in the case of salmon. However, the maximal whole fish rigor strength was judged to be about the same for both species. Moreover, the reductions in fillet area and length, as well as the increases in width, were basically of similar magnitude for both species. In fact, the increases in fillet roundness and cross-section height were larger for the cod. We conclude that the computer vision method can be used effectively for automated monitoring of changes in 2D and 3D shape and size of fish fillets during rigor mortis and ice storage. In addition, it can be used for grading of fillets according to uniformity in size and shape, as well as measurement of fillet yield measured in thickness. The methods are accurate, rapid, nondestructive, and contact-free and can therefore be regarded as suitable for industrial purposes.     

Shelf life extension of Atlantic pomfret (<Emphasis Type="Italic">Brama brama</Emphasis>) fillets by packaging under a vacuum-skin system

The present study was aimed at improving the commercialisation strategies of Atlantic pomfret (Brama brama), a medium-size fish commonly consumed as fresh fish. With this purpose, an innovative vacuum-skin packaging system including a surface thermal treatment was tested on Atlantic pomfret fillets stored at 4 °C for up to 19 days. The results were compared with traditional vacuum packaging carried out in parallel. The investigation of three sensory features (flesh appearance, flesh odour and flesh colour), five biochemical parameters (pH, free fatty acids, conjugated dienes, fluorescent compounds and total volatile bases) and three microbiological parameters (aerobic mesophiles, anaerobes and coliforms) was carried out in both batches. The vacuum-skin packaging system showed an interesting preservative effect leading to a significantly higher quality retention and longer shelf life (12 days) with respect to both traditional vacuum packaging (7 days) and a control batch kept in air (5 days). From the results obtained, it is concluded that the vacuum-skin system allows an extended shelf life and a better maintenance of the sensory, biochemical and microbiological quality of Atlantic pomfret fillets. This innovative packaging system might be applied to other kinds of fish species to stimulate the marketing opportunities.     

Biochemical,physical and sensory quality of ice-stored Atlantic cod (<Emphasis Type="Italic">Gadus morhua</Emphasis>) as affected by pre-slaughter stress,percussion stunning and AQUI-S<Superscript>™</Superscript> anaesthesia

Biochemical, physical and sensory quality of farmed Atlantic cod subjected to percussion stunning (control), anaesthesia (AQUI-S^™) and excessive exercise (30 min chasing before slaughter, ‘stressed’) were analysed after 7 days of ice storage. The white muscle energy status (initial pH, muscle twitches and high-energy phosphates) revealed that the fish were truly representatives of rested (percussion stunned and anaesthetised) and stressed cod. Sensory evaluation showed that the fillets of cod exposed to percussion stunning and AQUI-S^™ anaesthesia prior slaughter had slightly higher whiteness scores, and that the fillets of AQUI-S^™ anaesthetised cod had slightly shinier surfaces than the fillets of cod exposed to pre-slaughter stress. Furthermore, fillets of anaesthetised (AQUI-S^™) cod had significantly higher inosine monophosphate (IMP) contents and lower K-values than fillets of cod exposed to pre-slaughter stress, after 7 days of ice storage. Pre-slaughter stress did to some extent affect fillet colour immediately after killing and after ice storage. Otherwise, no significant effects of stress were observed with regard to biochemical, physical or sensory quality (ultimate pH, water content, drip loss, water holding capacity, texture and gaping) of farmed Atlantic cod.     

Computer vision-based sorting of Atlantic salmon (Salmo salar) fillets according to their color level

ABSTRACT:  Computer vision method was used to evaluate the color of Atlantic salmon ( Salmo salar ) fillets. Computer vision-based sorting of fillets according to their color was studied on 2 separate groups of salmon fillets. The images of fillets were captured using a digital camera of high resolution. Images of salmon fillets were then segmented in the regions of interest and analyzed in red, green, and blue (RGB) and CIE Lightness, redness, and yellowness (Lab) color spaces, and classified according to the Roche color card industrial standard. Comparisons of fillet color between visual evaluations were made by a panel of human inspectors, according to the Roche Salmo Fan™ lineal standard, and the color scores generated from computer vision algorithm showed that there were no significant differences between the methods. Overall, computer vision can be used as a powerful tool to sort fillets by color in a fast and nondestructive manner. The low cost of implementing computer vision solutions creates the potential to replace manual labor in fish processing plants with automation.     

Effects of microbial transglutaminase added edible coatings based on heated or ultrasound-treated whey proteins in physical and chemical parameters of frozen Atlantic salmon (Salmo salar)

The effects of the addition of transglutaminase to heated or ultrasound-treated whey protein coatings on quality parameters of frozen Atlantic salmon (Salmo salar) were evaluated. The influence of the type of denaturation treatment (heating or sonication) was also studied. The addition of microbial transglutaminase to the coatings did not significantly modify the yields, drip losses, colour and chemical composition of the fish fillets. The yields were higher in the samples protected with heated coatings than in those with ultrasound-treated ones. Transglutaminase addition to heated whey protein coatings delayed lipid oxidation. Ultrasound-treated coatings with or without enzyme addition were equally effective for lipid oxidation reduction after frozen storage of Atlantic salmon than heated-treated transglutaminase-added coatings.     

Concentration Measurement by Acoustic Reflectance

ABSTRACT The speed of sound and the acoustic reflection coefficient of sucrose (0 to 60 wt%), glycerol (0 to 50 wt%), sodium chloride (0 to 27 wt%) solutions and tomato ketchup (0 to 100 wt%) dispersions were measured using a modified pulse-echo technique (2.25 MHz transducer, 20 °C). The density of all solutions is measured using a vibrating tube densitometer. All measured parameters are linear functions of concentration. Ultrasonic reflectance can provide equally precise measurements of concentration as conventional ultrasonic velocity measurements. For all samples except concentrated ketchup (> 50 wt%), measured reflectance is demonstrated to be a function of ultrasonic velocity and density.     

LIPID CHANGES IN FROZEN STORED FILLETS FROM PRE- AND POSTSPAWNED HAKE (MERLUCCIUS HUBBSI MARINI)

The lipid composition of frozen stored fillets from pre‐ and postspawned hake was studied. The total lipid (TL) content in the chloroform/methanol extract from unfrozen postspawned hake was four times higher than that of prespawned fish. After freezing, the TL content of postspawning hake muscle remained unchanged whereas the TL extracted from prespawning fish muscle increased about 90%. The TL extractability of muscle from fish in both different gonadal conditions was not affected by frozen storage. Lipolysis in frozen stored fillets from prespawned hake occurs principally by hydrolytic action on phospholipids (PL), and phosphatidylcholine was the main PL hydrolyzed. Triacylglycerols were the main substrates hydrolyzed in frozen stored fillets from postspawned hake. Freezing and frozen storage affected polyenoics and n‐3 fatty acids (FA). The decrease in the contents of n‐3 FA in fillets from postspawned hake was lower than that observed in fillets from prespawned fish.     

EFFECTS OF TRIMMING AND COOKING BY SEVERAL METHODS ON POLYCHLORINATED BIPHENYLS (PCB) RESIDUES IN BLUEFISH

Bluefish were captured in the Atlantic Ocean near Long Island to study the effects of trimming and cooking on reduction of residues of polychlorinated biphenyls (PCBs). The mean concentration (standard error) of PCBs in the raw untrimmed fillets of the fish captured was 1.76 ± 0.17 ppm on a dry weight basis with range of 0.58 to 7.47. A direct relation between the concentration of PCBs in the raw fish fillets and their fresh weight showed a correlation coefficient of only 0.39. About twice the concentration of PCBs were found in the skins as compared to the dorsal and ventral sections of the raw fillets. Trimming the fillets resulted in a reduction in PCB residues averaging 59.4% with a further average reduction of 7.4% from baking, broiling, frying or poaching. There were no significant (p > 0.05) differences among the combined trimming and various cooking methods in the magnitude of reduction of PCB residues. The total quantities of PCBs found in the oil collected after baking, broiling or frying the fillets were less than could be accounted for as total cooking losses thus indicating that vaporization of PCBs during cooking may also occur.     

Sensory evaluation of Atlantic salmon fed three types of herring-based diet

Atlantic salmon (Salmo salar) were fed three different types of commercial and experimental herring-based feeds and, at the end of the feeding trials, sensory panels evaluated the acceptability of the salmon fillets. The feeds were all made from Atlantic herring but using different procedures: silage feeds were made from fermented herring, moist salmon feeds from fresh herring, and dry feeds from herring meal. Silage feeds were compared with either one or two of the other feeds in three feeding trials. Growth rates of animals fed a commercial silage feed and two dry feeds were similar, although growth on the commercial silage feed tended to be better. However, growth on commercial or experimental silage feeds was significantly lower (P < 0·001) than on either commercial or experimental moist feeds. Analysis of covariance indicated that there were no significant tank effects. At the end of the feeding trials, sensory evaluation of fish fillets by triangle test indicated no significant difference (P > 0·05) in fillet flavours or appearance between fish fed silage and fish fed the other diets.