Cod Flesh Research Articles

Anisakid parasites (Nematoda: Anisakidae) in 3 commercially important gadid fish species from the southern Barents Sea, with emphasis on key infection drivers and spatial distribution within the hosts.

Northeast Arctic cod, saithe and haddock are among the most important fisheries resources in Europe, largely shipped to various continental markets. The present study aimed to map the presence and distribution of larvae of parasitic nematodes in the Anisakidae family which are of socioeconomic and public health concern. Fishes were sourced from commercial catches during winter or spring in the southern Barents Sea. Samples of fish were inspected for nematodes using the UV-press method while anisakid species identification relied on sequencing of the mtDNA cox2 gene. Anisakis simplex (s.s.) was the most prevalent and abundant anisakid recorded, occurring at high infection levels in the viscera and flesh of cod and saithe, while being less abundant in haddock. Contracaecum osculatum (s.l.) larvae, not found in the fish flesh, showed moderate-to-high prevalence in saithe, haddock and cod, respectively. Most Pseudoterranova spp. larvae occurred at low-to-moderate prevalence, and low abundance, in the viscera (Pseudoterranova bulbosa) and flesh (Pseudoterranova decipiens (s.s.) and Pseudoterranova krabbei) of cod, only 2 P. decipiens (s.s.) appeared in the flesh of saithe. Body length was the single most important host-related factor to predict overall abundance of anisakid larvae in the fish species. The spatial distribution of Anisakis larvae in the fish flesh showed much higher abundances in the belly flaps than in the dorsal fillet parts. Trimming of the flesh by removing the belly flaps would reduce larval presence in the fillets of these gadid fish species by 86–91%.

Changes in Enzymatic Activity of Fish and Slaughter Animals’ Meat after High Pressure Treatment at Subzero Temperatures

The aim of this study was to determine changes in the activity of proteolytic enzymes and transglutaminase of fish and mammal meat after pressurization at subzero temperatures. The activity was measured at the optimal pHs determined for enzymes from particular types of tested meat. It was found that increasing the pressure in the range of 60-193 MPa, did not change significantly the activity of acidic proteases of cod flesh, while the activity of neutral and alkaline proteases decreased drastically. Proteolytic enzymes from salmon flesh were more resistant than those from cod flesh. They maintained or increased (neutral protease) activity after pressurization. The activity of the endogenous enzymes of bovine meat increased with pressure increase, except for acidic proteases, the activity of which was reduced after treatment at 193 MPa to the level similar to unpressurized meat. Endogenous proteases of porcine meat were activated by high-pressure treatment. It has been shown that activity of TGase in unpressurized flesh from cod was 5 times higher than that from unpressurized salmon. Depending on the type of meat, these enzymes were also significantly different in their sensitivity to pressure. The pressure of 60 and 193 MPa led to a complete inactivation of the TGase in cod flesh, while the activity of salmon flesh TGase was decreased only by 15 and 21%, respectively.

Antioxidants from barley husks impregnated in films of low‐density polyethylene and their effect over lipid deterioration of frozen cod (Gadus morhua)

The changes in quality of cod fillets packaged in films with and without antioxidants during 12 months of frozen storage at - 20 °C were investigated in the present study. The following parameters were determined in order to study lipid hydrolysis and primary and secondary lipid oxidation in the samples during frozen storage: peroxide value, conjugated dienes, conjugated triene hydroperoxides, free fatty acids, totox value, thiobarbituric acid-reactive substances and p-anisidine value. Films containing antioxidants isolated from barley husks were effective in slowing down lipid hydrolysis and primary and secondary lipid oxidation processes. Secondary lipid oxidation reached maximum values in the 12th month of storage in control samples and samples packaged with antioxidant-containing film. Maximum lipid hydrolysis and lipid oxidation values for control cod samples were significantly higher than the maximum values found in samples packaged with antioxidant-containing film. The results confirm the efficacy of natural antioxidants derived from barley husks in slowing down lipid hydrolysis and increasing the oxidative stability of cod flesh. They also demonstrate the potential usefulness of natural antioxidants extracted from barley husks in the development of active packaging films for food preservation.

Decreased lipid storage in juvenile Atlantic cod (Gadus morhua) during settlement in cold-water eelgrass habitat

We characterized the prey field and the lipid classes/fatty acids in the flesh of age 0 juvenile cod (Gadus morhua) during their late-summer/fall arrival and settlement into eelgrass (Zostera marina) in coastal Newfoundland. Examination of available prey demonstrated a high abundance of small zooplankton (Acartia, Microsetella and Oithona sp.) with no larger Calanus sp. prey. Breakpoint analysis showed significant changes in the accumulation of relative (mg g−1 wet weight) and absolute (μg fish−1) amounts of lipid with standard length at the time of settlement (~60 mm standard length). Settling juvenile cod showed an alternate lipid utilization strategy where they catabolized phospholipids (PL) to a greater extent than triacylgylcerols (TAG). Polyunsaturated fatty acids (PUFA) content in cod flesh decreased as fish grew indicating that nearshore zooplankton quality was not optimal for PL formation. The dramatic reduction in cod PL was likely due to both catabolism of muscle and a lack of dietary PUFA suitable for PL synthesis. However, juvenile cod continued to grow, leading to decreased lipid stores and suggesting that cod settling into eelgrass are under intense selection pressure for growth prior to the onset of winter, possibly as a means of escaping gape-limited predation. These data contrast better-studied freshwater and estuarine systems in which lipid storage is critical for successful overwintering.

ROLE OF INITIAL MUSCLE pH ON THE SOLUBILITY OF FISH MUSCLE PROTEINS IN WATER

The solubility of the myofibrillar and cytoskeletal proteins in water was determined for the muscle tissue often species offish. The flesh of six white-muscled fish had pH's at the time of processing above pH 6.6 and greater than 80% of their myofibrillar/cytoskeletal proteins were soluble in water. The flesh of three pelagic species and a shark had pH values when processed below 6.6 and the water solubility of their myofibrillar and cytoskeletal proteins was less than 40%. When the washed minced muscle of one of the white-fleshed species, cod, was exposed to low pH, the solubility of its myofibrillar and cytoskeletal proteins decreased substantially. The water solubility of the cod myofibrillar and cytoskeletal proteins could be reestablished by washing the acid-treated cod flesh with neutral salt solutions. It is suggested that pH values below 6.6 modify certain proteins which prevent the water-extractability of the rest of the myofibrillar and cytoskeletal proteins from being expressed.

Selective capture of blue cod Parapercis colias by potting: behavioural observations and effects of capture method on peri-mortem fatigue

Selective fishing is the successful capture of target species and size classes in a way that minimises bycatch, minimises damage to flesh, and maximises post-mortem (PM) value. We studied selective harvesting of blue cod Parapercis colias (Pinguipedidae) in central New Zealand, where it is captured mainly by commercial pot-fishing and recreational line-fishing. Potting with paua Haliotis iris (=abalone) guts selectively targeted large blue cod from localities that had six or more fish species and many small blue cod. Video observations of pot entries indicated that blue cod entered and left the pot throughout 30 min sets. Blue cod were observed by video to commence swimming when pot-hauling started. Observations of line-hooked fish indicated a characteristic spinning behaviour while hauling. Fatigue during harvesting is a major factor in reducing the PM quality and shelf-life of fish muscle. Despite the relatively benign nature of capture via pot, it appears that burst exercise during hauling and a brief flurry of flapping as the pot leaves the water is sufficient to compromise flesh quality. Fish that were fatigued during harvesting had a poorer peri-mortem ‘ATP potential’ than fish that had been tank-rested for a year and then harvested using rested harvesting techniques. Modifying the potting method by providing a reservoir of water reduced peri-mortem fatigue during capture but by an insufficient amount to significantly improve PM flesh quality. Blue cod flesh is compromised by pot capture, which is widely perceived as a benign harvesting method. In order to maximise value of blue cod, low-stress harvesting methods which take advantage of the behaviour of the fish are required.

Application of chemometrics to low-field1H NMR relaxation data of intact fish flesh

The possibilities for application of low-field 1H nuclear magnetic resonance (NMR) as a rapid method for simultaneous assessment of basic quality parameters in fish were explored. In a first experiment, 200 salmon (Salmo salar) samples mapping the variation over an entire fish were measured by NMR and subsequently analysed for oil or water content by standard chemical methods. In a second experiment, 58 differently thawed cod (Gadus morhua) samples were measured by NMR and subsequently analysed for water-holding capacity. Correlations between chemical data and NMR data were evaluated using partial least squares (PLS) regression on complete relaxation curves and compared with conventional regression models on exponential fitting parameters. Predictions on an independent test set were superior for the PLS regression models, with optimal prediction errors of 12 g kg−1, 6 g kg−1 and 3.9% for oil and water content in fresh salmon flesh and water-holding capacity in thawed cod flesh respectively. Thus rapid, non-invasive low-field NMR can be used to simultaneously determine both oil and water content of fish flesh. Furthermore, it can predict water-holding capacity of cod flesh, with an R2 of 0.9 over the range 30–90%, as determined by a centrifuge test. © 1999 Society of Chemical Industry

The Improved Whitening of Minced Cod Flesh Using Dispersed Titanium Dioxide

A simple effective method of whitening fish mince using titanium dioxide has been developed. The whitener comprised a dispersed titanium dioxide (TiO2) suspension stabilised with xanthan gum (20 g TiO2/1 g xanthan gum/79 ml water) which produced significant whitening of fish mince derived from cod waste. The whitener was incorporated during the mixing stage of conventional fish mince manufacture, and achieved an even spread of coloration. The whitened fish mince was found to be stable to high temperature cooking systems, such as frying. Taste and texture of the fish mince were not affected by the level of xanthan gum and TiO2 used. Xanthan gum and TiO2 were sufficiently heat stable and inert with respect to taste, odour and chemical reactivity, to be suitable for use for such a purpose, unlike other compounds investigated and conventional dispersed fat/oil whiteners. A level of 1 g kg-1 of TiO2 in the fish mince was found to give optimal level. © 1997 SCI.

The Improved Whitening of Minced Cod Flesh Using Dispersed Titanium Dioxide

A simple effective method of whitening fish mince using titanium dioxide has been developed. The whitener comprised a dispersed titanium dioxide (TiO2) suspension stabilised with xanthan gum (20 g TiO2/1 g xanthan gum/79 ml water) which produced significant whitening of fish mince derived from cod waste. The whitener was incorporated during the mixing stage of conventional fish mince manufacture, and achieved an even spread of coloration. The whitened fish mince was found to be stable to high temperature cooking systems, such as frying. Taste and texture of the fish mince were not affected by the level of xanthan gum and TiO2 used. Xanthan gum and TiO2 were sufficiently heat stable and inert with respect to taste, odour and chemical reactivity, to be suitable for use for such a purpose, unlike other compounds investigated and conventional dispersed fat/oil whiteners. A level of 1 g kg-1 of TiO2 in the fish mince was found to give optimal level. © 1997 SCI.

Larval Anisakis simplex (Nematoda: Ascaridoidea) Infection in the Musculature of Atlantic Cod, Gadus morhua, from Newfoundland and Labrador

Larvae of Anisakis simplex were found in the flesh of Atlantic cod, Gadus morhua, collected in 21 regions around Newfoundland and Labrador during 1985–87. Prevalence and abundance increased with cod size and varied geographically; cod off Labrador had the fewest larvae whereas those from the south coast of Newfoundland were the most heavily infected. Most larvae (~95%) occurred in flesh surrounding the body cavity (napes), with a significantly higher percentage of the nematodes (~58%) in the flesh on the left side. In 505 cod in which all tissues were examined, 85.6, 10.8, and 3.5% of the A. simplex resided in the body cavity and viscera, napes, and fillets, respectively. Cod surveyed tended to have more A. simplex in the musculature than those from other areas off eastern Canada, but are lightly infected compared with most other Atlantic cod stocks. The examination method (candling combined with slicing) recovered, on average, 42% of the A. simplex present in the flesh; consequently, infection statistics reported here are underestimates. Numbers of A. simplex in cod off Labrador and eastern Newfoundland are similar to those observed during 1947–53, but the abundance of A. simplex appears to have increased among cod from NAFO Subdivision 3Pn.

Serial Passage of Larval Pseudoterranova decipiens (Nematoda:Ascaridoidea) in Fish

In one experiment, 24 brook trout (Salvelinus fontinalis) in fresh water at 11 ± 1 °C were each orally infected by intubation with two third-stage larvae of "sealworm" (Pseudoterranova decipiens) harvested from the flesh of sea raven (Hemitripterus americanus) and small Atlantic cod (Gadus morhua). In a second experiment, 27 cod in sea water at 0 °C were each force fed, under anaesthesia, four P. decipiens larvae held in a capelin "purse"; these larvae were harvested from large, commercial size cod. Sequential reinvasion by the same P. decipiens larvae was achieved in both of the serial passage experiments. In brook trout, larvae sequentially reinvaded a maximum of two fish, with larvae of cod origin being the more successful at first passage (62.5%) than those of sea raven origin (31.3 and 37.5%). In cod, larvae also achieved sequential reinvasion of a maximum of two fish; the relatively lower success rates of 22.2% (first passage) and 9.1% (second passage) probably reflect the low temperature (0 °C) at which the experiment was conducted.

OMEGA-3 FATTY ACID LEVELS AND PERFORMANCE OF BROILER CHICKENS FED REDFISH MEAL OR REDFISH OIL

Arbor Acre broiler chickens were fed six different diets to determine if the omega-3 fatty acid content of broiler chicken carcasses could be enhanced by feeding additional redfish meal (RFM) or redfish oil (RFO). The six diets were: control (no fish meal or fish oil); 7.5% RFM, 15.0% RFM, 30.0% RFM, 2.1% RFO and 4.2% RFO. Mortality at 28 d and 42 d was lower (P < 0.05) for birds fed RFO compared to those fed RFM. Feeding additional RFM or RFO had no (P > 0.05) effect on mortality, but resulted in lower body weights (P < 0.01) and feed consumption (P < 0.05) and poorer (P < 0.05) feed conversion. Additions of RFM or RFO to the diets resulted in a substantial dietary enrichment of omega-3 fatty acids (especially eicosapentaenoic acid, EPA or 20:5n-3; and docosahexaenoic acid, DHA or 22:6n-3). Analyses (wt/wt %) revealed that breast meat was lower (P < 0.001) in lipid and triglyceride but higher in cholesterol esters (P < 0.005), free cholesterol (P < 0.001) and phospholipid (P < 0.001) than thigh meat. Lipid, free cholesterol and phospholipid of edible meat lipid increased with duration of feeding (14 d, 28 d, 42 d) but triglyceride content decreased. Dietary treatment had no effect (P > 0.05) on carcass lipid content or composition. Breast meat lipid contained more (P < 0.001) of the omega-3 fatty acids (especially EPA and DHA), more n-3 docosapentaenoic acid (DPA or 22:5n-3) and more total n-3 polyunsaturated fatty acid (n-3 PUFA) than thigh meat lipids. EPA, DPA, DHA and total n-3 PUFA in edible meat lipids increased (P < 0.05) with duration of feeding. Feeding additional RFM and RFO resulted in an increased accumulation of the EPA (P < 0.001), DPA (P < 0.01), DHA (P < 0.01) and total n-3 PUFA (P < 0.001), primarily at the expense of the omega-6 fatty acids linoleic (18:2n-6) and arachidonic (20:4n-6). It can be calculated from the data presented that on average a normal meal (100 g) of chicken which has been fed 7.5% fish meal, would contribute 140 mg of omega-3 fatty acids (EPA + DPA + DHA). The same size meal of cod flesh would contribute about 135 mg of these fatty acids. Key words: Broiler chickens, breast, thigh, redfish meal, eicosapentaenoic acid, omega-3 fatty acids

LITERATURE ABSTRACTS

LITERATURE ABSTRACTS

Mass spectra of fatty acid derivatives, of isopropylidenes of novel glyceryl ethers of cod muscle and of phenolic acetates obtained with the Finnigan MAT Ion Trap Detector.

The applicability of the Finnigan MAT Ion Trap Detector (ITD) mass spectrometer for structure determination in some selected fatty acids and their derivatives has been investigated. Isopropylidene derivatives of novel glyceryl ethers isolated from cod flesh and of phenolic acetates are included to indicate the potential for diverse structures and to clarify the protonation of ions. The ITD is a simple and unsophisticated gas liquid chromatograph-mass spectrometer, but the spectra obtained are in most respects comparable to those from more conventional electron impact mass spectrometers. However, due to the comparatively high background pressure (approximately 10(-3) torr) in the ionization chamber of the ITD, there is a tendency for both neutral and ionized molecules to acquire protons from other molecules or fragments through collision. In many cases, the molecular ion was observed as the protonated molecular ion (M + 1), as in chemical ionization mass spectrometry. These interactions can be minimized if the sample load is decreased. Phenolic acetates exhibit not only protonation of the molecular ion, but also protonation of stable fragmented neutral molecules or ions.

Meat Textured Fish Protein Concentrate from Minced Cod (Gadus Morhua)

The objectives of this study were, firstly, to prepare a meat textured fish protein concentrate (marinbeef) from minced flesh of Atlantic cod (Gadus morhua) and, secondly, to determine its suitability as a meat replacer for the Canadian consumer. The final product had a moisture content of 9–10%, a crude fat content of 0.15–0.19% and a rehydration capacity of 3.0–3.5 (w/w). The product yield was approximately 10% of the initial weight of minced fish. Sensory tests showed that the acceptance of a hamburger product was not affected when approximately 30% of the ground beef was replaced by rehydrated marinbeef or when 45% of the ground beef was replaced by rehydrated marinbeef plus fat. Sensory tests also showed that the acceptability of a sausage product was not significantly affected when approximately 30% of the meat constituents of the sausage were replaced by rehydrated marinbeef. The rehydrated product was flavorless, had an off-white color, and a texture very similar to cooked ground beef. These results indicate fish protein concentrate prepared from minced cod flesh by the “marinbeef process” can function as a meat replacer in hamburger and sausage products.

Effect of fat content on protein fractions and textural properties of minced cod flesh in the course of frozen storage

In this study minced cod flesh, with the addition of 4%, 8% and 10% cod liver oil, was maintained in frozen storage for periods of up to 12 months. The changes in protein fraction of the tissue was determined during frozen storage and found to be dependent on lipid content and rate of freezing. The effects of peroxide content, carbonyl compounds and lipid fractions on the solubility of myofibrillar proteins in cod muscle tissue, and the changes of cod mince consistency arising from changes in protein fraction and lipid content in frozen storage, are discussed.

Effect of Delayed Filleting on Quality of Cod Flesh

ABSTRACTA study was undertaken to determine the effect of delayed filleting on overall shelf life of cod. One lot of gutted cod was divided into three groups for iced storage and filleted 1,4 or 7 days postmortem. Quality of fillets during subsequent storage at 1–2°C was assessed by physical characteristics, trimethylamine values, and total aerobic plate counts. After day 7, comparison of fillets of the same postmortem age showed that fish which had been most recently filleted was superior to that processed one day after landing, and stored subsequently in plastic trays. Results indicated that maximum overall shelf life could be attained by minimizing time stored as flllets, i.e. delaying filleting.

Effect of accumulated free fatty acid on reduction of salt soluble protein of cod flesh during frozen storage.

The effect of the free fatty acid (FFA) released from phospholipids by the action of lipolytic enzymes on protein denaturation of fish flesh during frozen storage was studied. The FFA content and the salt soluble protein extractability of commercially available frozen “surimi” were determined. The results obtained suggest that there may be a definite negative interrelation between the FFA content and the salt soluble protein extractability. Minced cod flesh was washed thoroughly with cold water, mixed with phospholipase A2 specimen, and stored at -16°C for 24 weeks. The FFA content incerased rapidly accompanied with marked decreases of polar lipids due to added phospholipase A2 during storage for first one week. The content of salt soluble protein increased during storage for up to 1-2 weeks and then decreased gradually to the minimum amount after storage for 6 weeks. The length of storage period up to the time when the content of salt soluble protein reached the minimum amount was shorter in the test-sample than in the control-sample without added phospholipase A2. From these results, it is presumed that the FFA released from phospholipids by the action of added phospholipase A2 induces the reduction of salt soluble protein extractability, though some oxidation products of lipids may contribute to the reduction of salt soluble protein extractability to some extent.

Inorganic salts and extractability of fresh and frozen fish proteins

Changes in protein extractability (PE) were followed in minced cod meat and in meat washed with distilled water containing added NaCl, KCl, MgCl 2, CaCl 2, and phosphates. In minces stored for 24 h at 4°C and pH 5.5–7.2 the PE decreases with increasing acidity. The same is also true in samples containing 0.2 M of added NaCl 100 g −1 or KCl 100 g −1, while in the presence of MgCl 2 and CaCl 2 in the same concentration PE is very significantly lower than in the control and does not depend so much upon the acidity of the mince. In water extracted and frozen minces after two weeks at−20°C at pH 7.2 and 6.4 the PE is 25% and 50% lower, respectively, than before freezing. NaCl, KCl, MgCl 2, and CaCl 2 added to the washed meat in concentrations corresponding to μ = 0.15 decrease the PE after two weeks of frozen storage by about 7%, 20%, 16%, and 43%, respectively. At μ>0.25, KCl, phosphates, and KCl+CaCl 2 have, during two weeks, a protective effect on PE. In water extracted mince PE decreases after 1 d at −20°C by 15%, which corresponds to a drop in PE in unextracted samples at pH 6.9 only after five weeks. A mixture of salts added to the water extracted mince, corresponding in composition and μ to those in cod flesh, brings about, after prolonged frozen storage, a drop in PE much higher than that in extracted samples.

Phocanema decipiens: Growth, reproduction, and survival in seals

Captive harbor seals ( Phoca vitulina) and gray seals ( Halichoerus grypus) were fed infective larvae of Phocanema decipiens, an anisakine nematode from the flesh of Atlantic cod ( Gadus morhus). Ova of P. decipiens were first detected in the feces of harbor seals 21(17–30) days after exposure; the patency period was 15 to 45 days. In gray seals, the prepatent period was 19(16–23) days; patency 20–60 days. By the sixth week of infection in harbor seals, mean body lengths of adult females and males of P. decipiens were 60.8(40.8–76.2) and 54.3(45.5–60.8) mm, respectively; mean fecundity of female nematodes was 156,000 ova. In infections of similar duration in gray seals, females and males of P. decipiens were 82.1(69.7–104.3) and 64.4(53.8–72.7) mm in length, respectively; mean fecundity of females was 366,000 ova. In sensitizing infections in harbor seals, 28% of P. decipiens survived to early patency (Days 25–30) while only 9% of the nematodes survived to midpatency (Days 35–45). In sensitizing infections in gray seals, 56% of P. decipiens survived to early patency (Days 20–30) and 48% survived to midpatency (Days 35–50). Seals with existing or recent P. decipiens infections resisted reinfection; <50% of the nematodes in challenge infections in gray seals survived to Day 3 and <10% survived to patency. Growth of the nematodes, however, was not retarded in the challenge infections and resistence to reinfection subsided when seals were maintained anisakinefree for 2–6 months after loss of prior natural or experimental infections. Natural anisakine infections were surveyed in 16 harbor and 53 gray seals from the Nova Scotia mainland. The mean incidence of P. decipiens was 62(5–177) in harbor seals and 577(11–1694) in gray seals; incidence varied seasonally and with age of host. Adult females of P. decipiens from harbor seals were 64.0(49.2–79.8) mm in length and contained 1.68(0.87–2.73) × 10 5 ova; females from gray seals were 78.3(62.3–92.1) mm in length and contained 2.39(0.69–4.39) × 10 5 ova.