Cod Fillets Research Articles

The effects of a beef and fish meal on plasma amino acids, insulin and glucagon levels

In vivo studies have reported the effects of various protein meals on pancreatic hormone secretion. The purpose of the present investigation was to compare the plasma insulin, glucagon and amino acid variations in response to a beef or a fish meal with comparable amino acid content. It was found that the plasma insulin levels increased significantly more with the beef steak meal (from 46.2 ± 3.5 to 153.2 ± 12.6 pmol/l) than with the cod fillet (from 47.8 ± 3.1 to 104.2 ± 9.7). The increase in plasma glucagon following the beef meal (from 64.2 ± 8.1 to 139.4 ± 21.9) was not significantly different from that of the fish meal (from 64.2 ± 7.6 to 119.8 ± 17.8). The increase in plasma amino acids was comparable for both meals except for arginine and lysine which were higher with fish feeding and for histidine when beef was fed. The plama levels of histidine were 30 μmol/l compared to 10μmol/l for the fish meal. This difference may be related to the fact that carnosine, a dipeptide composed of histidine and beta-alanine, is found in high concentrations in beef muscles but is relatively absent in cod fillets. Postprandial studies on time-related variations of plasma histidine and on digestibility or rate of absorption of beef and fish meat are needed in order to identify the factor involved in the difference in insulin secretion between these two nutrients.

Protein Meals and Postprandial Thermogenesis

In North America the consumption of meat far exceeds that of fish. Because the palatability of the food has been shown to influence the thermogenic response to feeding, a study was designed to compare the metabolic response to 195-g beef steak and 250-g cod fillet containing both 43 g of proteins in a first experiment and to 250 g of both nutrients in a second experiment. The subjects who participated in this study gave a higher rating of palatability (obtained on a 10-cm visual analog scale) when the beef steak (7.4) was consumed compared to the cod fillet (3.0). Measurements of oxygen consumption during the cephalic phase (0 to 40 min) indicated a larger thermogenic response to the beef than to the fish meal. These findings suggest that the thermic response to feeding during the cephalic phase are related to the sensory stimulation of the meal. During the gastrointestinal phase (40 to >180 min) the response was not influenced by the type of food and was related instead to the amount of proteins ingested. Plasma amino acid determinations indicated differences between the beef and fish feeding. Plasma histidine and glutamine was higher after beef feeding. The meaning of these findings does not seem to be related at this time to the results obtained on postprandial thermogenesis. The increases in plasma insulin that were observed during both phases of feeding were similar for the beef and the fish meals. Despite a marked increase of insulin, plasma glucose remained unchanged after feeding either meals, suggesting an enhanced gluconeogenesis and an increased glucose utilization.

CATALASE ACTIVITY AS AN INDEX OF MICROBIAL LOAD AND END‐POINT COOKING TEMPERATURE OF FISH

AbstractPsychrotrophs that are responsible for spoilage of many aerobically cold‐stored foods are strongly catalase positive. This study was conducted to ascertain the feasibility of using the Pasteur pipette catalase test developed by Fung (1985) to estimate the microbial population in raw fish during aerobic cold storage and to determine the end‐point cooking temperature of fish. Fish samples (cod fillets, catfish, halibut fillets, rainbow trout, and salmon fillets in three replications each) were stored at 7C and monitored at 0, 6, 12, 24, 48, and 72 h and up to 7 days. Fish surface, fish juice, and fish meat samples were obtained by conventional microbiological methods and were serially diluted in 0.1% of peptone water to a final 1:100 dilution. To perform the catalase test 0.1 mL of the 1:10 or 1:100 dilution of the sample was placed into the wider portion of the heat‐sealed Pasteur pipette followed by 0.1 mL of 3% H2O2. The liquid mixture then was shaken into the heat‐sealed capillary portion. The pipette was then inverted and after 5 min, the lengths of the gas column and the liquid column were measured in mm; the gas column was expressed as a percentage of the total, which was considered as the percentage catalase activity (% CA). Viable cell counts (VCCs) of these samples also were made. As VCCs increased on fish surface, in fish juice, and in fish meat samples, concomitant increases occurred in % CA. The lowest level detect by this method was about 103‐4 CFU/cm2, mL, or g. Catalase activities of 0.0‐0.5% on fish surface, <4.3% in fish juice, and <2% in fish meat, corresponded to low total counts of 104‐5 CFU/cm2, 105 CFU/mL, and 103‐4 CFU/g, respectively. Catalase activities of 0.6‐1.5% on fish surface, 4.3‐8.2% in fish juice, and 2.3‐5% in fish meat, corresponded to high total counts of 106 CFU/cm2, 106 CFU/mL, and 105‐6 CFU/g, respectively. Catalase activities of 1.7‐2.5% on fish surface, 8.3‐12.4% in fish juice, and 5–6% in fish meat, indicated that fish was unacceptable for consumption. Fish samples were cooked at temperatures of 40C, 50C, 55C, 60C, 65C, 70C, and 75C to determine the end‐point temperature. Each sample was heated at each temperature for: 36 s, 1 min, 2 min, 3 min, and 5 min in a temperature‐controlled water bath. Samples that had reached an internal temperature of 65C showed no catalase activity in the test tube method or very little activity in the capillary tube method and contained no live bacteria, indicating that fish was safe for consumption.

Thawed Cod Fillets Spoil Less Rapidly Than Unfrozen Fillets When Stored under Modified Atmosphere at 2°C

The effect of two months of frozen storage at −20°C on the spoilage characteristics and shelf life of thawed and modified atmosphere packed (MAP) cod fillets stored at 2°C was studied. Thawed MAP cod fillets were compared with fresh cod fillets stored in CO2-containing modified atmospheres with and without added oxygen. The shelf life of 11 to 12 days in the fresh MAP cod was extended to more than 20 days in the thawed MAP cod at 2°C. This shelf life extension was most likely due to the inactivation of the spoilage bacterium Photobacterium phosphoreum during frozen storage as reflected both in Chemical analyses and sensory evaluation. In contrast to fresh MAP cod fillets no significant production of trimethylamine occurred and almost no amine odor and taste were detected during 20 days of chill storage of thawed MAP cod fillets. The use of frozen fillets as raw material not only provides a more stable product in MAP but also allows much greater flexibility for production and distribution. However, a slightly increased concentration of dimethylamine, a larger drip loss, and detection of weak frozen storage flavor were observed in the thawed MAP cod fillets.

Specific Inhibition of Photobacterium phosphoreum Extends the Shelf Life of Modified-Atmosphere-Packed Cod Fillets

Inhibition of the specific spoilage organism, Photobacterium phosphoreum, was studied in model substrates and in modified-atmosphere-packed cod fillets. The objective was to determine how inhibition of this organism influenced spoilage. The spoilage reactions limiting shelf life were studied rather than the development of a new product. In naturally contaminated modified-atmosphere-packed cod fillets, 500 ppm Na2CaEDTA reduced the growth rate of P. phosphoreum by 40% and shelf life was increased proportionally by 40%, from 15 to 17 days to 21 to 23 days at 0°C. In aerobically stored cod fillets other microorganisms were responsible for spoilage and Na2CaEDTA had no effect on shelf life. The extension of the shelf life of modified-atmosphere-packed cod therefore was a result of the reduced growth of P. phosphoreum and no other microbial or nonmicrobial spoilage reactions limited shelf life. These results confirmed P. phosphoreum as the specific spoilage organism in modified-atmosphere-packed cod and showed the organism to have an extensive spoilage domain. Consequently, any preservation procedure able to reduce growth of P. phosphoreum is likely to extend shelf life of packed cod. However, the effect of different inhibitory compounds in model systems as well as results from packed cod indicated the need to include product studies in the screening of antimicrobials and in the development of preservation procedures.

Effects of beef steak and cod fillet on plasma glucose, insulin, amino acids and energy metabolism in normal subjects

The purpose of the present investigation was to compare and evaluate the plasma insulin change, the thermogenic response and the substrate utilization in response to a small(125g) and a large(250g) beef steak and cod fillet. Plasma glucose(mmol/L) which was 4,49 ± 0,2 for the small and 4,34 ± 0,2 for the large meal during the fasting state, remained unchanged for the duration of the postprandial period. Plasma insulin levels have shown various significant differences. The postprandial increase in plasma insulin was higher with the large than with the small meal independently of the type of meal and it was smaller with both sizes of meal at 180 than at 90 min. At 180 min the plasma insulin increase was significantly greater with the 125g beef steak meal than with the cod fillet. At both 90 and 180 min the increase of the average 9 essential amino acids with the small beef steak was larger than with the small cod fillet. Taken individually, the levels of leucine, valine and alanine were greater at 180 min for the 125g beef steak meal than for the cod fillet. With the 250g meals, no significant difference in the increase of amino acids were detected at 90 and 180 min between the two types of meals. Thermogenic measurements have shown a higher increase in oxygen consumption with the large meal than with the small one. The increase was also higher with the 125g meal at 180 min with the beef than with the fish meal. The substrate utilization results indicated a higher glucose oxidation with the small beef steak meal than with the cod fillet. It was also found that the lipid oxidation was always significantly higher than that of the carbohydrates with both the small and the large beef and fish meals. In all, the results show that the hormonal and metabolic responses following the small beef meal were significantly greater than those of the small fish meal and that the increase of plasma amino acids following a protein meal is an important factor for gluconeogenesis.

Importance of Frozen Storage Temperature in the Type of Aggregation of Myofibrillar Proteins in Cod (Gadus morhua) Fillets

Cod fillets were examined to determine the effect of two frozen storage temperatures (−20 and −30 °C) on the formation of aggregates and if this relates to changes in texture and functionality. The...

In vitro study of TMAO reduction by Shewanella putrefaciens isolated from cod fillets packed in modified atmosphere

A strain of Shewanella putrefaciens was isolated from cod fillets in a modified atmosphere (60% CO2, 30% O2, 10% N2). The effect of pH on the growth of Shewanella putrefaciens and TMAO reduction was studied in fish extract with citrate buffer systems at pH values from 5.8 to 6.8. The effect of the modified atmosphere (CO2, O2) on the growth of S. putrefaciens and on the reduction of TMAO to TMA was studied using solid media from fish extract packed under variable mixtures of CO2, O2 and N2 . All the samples were incubated at 7°C for 7 days. Slow development of S. putrefaciens and no production of TMA was observed in fish extract buffered at pH 5.8. Inclusion of O2in the packaging atmosphere of solid fish extract, even at small proportions (10%), was inhibitory for the reduction of TMAO, while there was no effect of O2on the growth of S. putrefaciens. Increased levels of CO2 (≥ 50%) in the atmosphere were inhibiting the growth of S. putrefaciens and consequently the production of TMA.

Development of Quality Index Methods for Evaluation of Frozen Cod (Gadus morhua) and Cod Fillets

Two experiments were conducted to develop schemes for the rapid assessment of quality characteristics of frozen cod and cod fillets that could be used in industry to evaluate incoming material and for use in production planning and quality management. Three separate schemes for thawed whole cod, fillets and cooked fillets were developed using the quality index method. The schemes were tested using chemical and physical methods as comparisons. Principal component analysis of sensory, chemical and physical data showed an inverse correlation between water-holding capacity and the other variables (dry matter, formaldehyde concentration, total volatile nitrogen). The cod were grouped according to the length of time they had been frozen. The results of the quality index method for both whole cod and cod fillets loaded onto the same position in the PC plots indicated they were assessing similar underlying phenomena.

Reduction of trimethylamine oxide byShewanellaspp. under modified atmospheresin vitro

Two strains ofShewanellaspp. were isolated from cod fillets packed in modified atmosphere (60% CO2, 30% O2, 10% N2). One of the strains was identified asShewanella putrefaciens. The other strain could not be fully identified but was determined as aShewanellaspp. different fromS. putrefaciens. The effect of modified atmosphere (CO2, O2) on the growth of the two strains and on the reduction of TMAO to TMA was studied using solid medium from fish extract packed under variable mixtures of CO2, O2and N2. All the samples were incubated at 7°C for 7 days. TheShewanella-like strain was shown to be a stronger TMAO reducer and was more resistant to CO2thanS. putrefaciens per se. Modified atmosphere packaging of marine fish can inhibit the growth and TMAO-reducing activity ofS. putrefacienswhen 50% of CO2together with 10% of O2are introduced into the packaging atmosphere. The growth and TMAO-reducing activity of theShewanella-like strain can be inhibited when higher proportions of CO2together with as high as possible proportions of O2are introduced into the packaging atmosphere. It is suggested that a combination of 60–70% CO2and 30–40% O2is introduced into the packaging atmosphere in order to prevent TMA production byShewanellaspp.

Application of an iterative approach for development of a microbial model predicting the shelf-life of packed fish

An iterative approach was used to develop a microbial model for shelf-life prediction of cod fillets packed in modified atmospheres. The effect of temperature (0–15°C) and CO2 (0–100%) on growth of the specific spoilage organism, Photobacterium phosphoreum, was studied in packed cod and in liquid media. P. phosphoreum was a dominant part of the spoilage microflora of packed cod stored at the extremes of the range of conditions studied. The organism is therefore likely to be important for spoilage and the development of a microbial model within this domain seems relevant. A liquid medium was developed to provide growth kinetics of P. phosphoreum similar to those observed in packed cod. Using this medium, the effect of temperature and CO2 on the maximum specific growth rate of Photobacterium phosphoreum was determined by absorbance measurements and modelled by a square root equation and by a polynomial equation. Product validation studies were carried out during summer and winter using naturally contaminated packed cod fillets which were stored at constant and at changing temperatures. The shelf-life of the packed fillets was predicted on the basis of the initial numbers of P. phosphoreum, product temperature profiles and the level of CO2 in the modified atmosphere. The average deviations between shelf-life determined by sensory evaluation and shelf-life predicted by the square root equation and by the polynomial equation were 17% and 9%, respectively.

Use of Ultrasound to Determine Cod Fillet Composition

ABSTRACTThe 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).

On Prices of Fresh and Frozen Cod Fish in European and U.S. Markets

The purpose of this paper is to test for price linkages among European (France, Germany, and U.K.) and U.S. prices of whole fresh cod and frozen cod fillets. In testing for a cointegrated system, we use both the two-stage Engle-Granger and Johansen procedures. Short-run price dynamics are measured using an error-correction model. Based on monthly import price observations from 1980 to 1992, the empirical results show no long-run price relationships for fresh cod between European and U.S. markets, but we do measure long-run price linkages for frozen cod fillets. Within Europe the markets for both fresh and frozen cod product are well integrated. The U.S. fresh cod market is distinct and separate from European markets, while the U.S. frozen cod market shows no short-run links to European markets. There is weak evidence for a long-run international market in frozen cod fillets.

Thawing, Refreezing and Frozen Storage Effects on Muscle Functionality and Sensory Attributes of Frozen Cod (Gadus morhua)

ABSTRACTThawing and re‐freezing of cod fillet blocks did not necessarily result in greater deterioration (relative to a ‘once frozen’ control) of cooked fish sensory attributes after 9 months frozen storage at –22°C. Thawed and refrozen fish muscle displayed a faster decline in myofibril protein solubility than once frozen controls and had reduced water‐holding capacity but analysis of proton spin‐spin relaxation times indicated no change in water location. The decline in protein solubility was not caused by complete protein unfolding. Long thawing times (30 hr) before re‐freezing and storage resulted in cooked fish with more gray appearance and more stale flavor. Changes in fish muscle functionality did not enable direct inference of sensory attributes.

Effect of modified atmosphere packaging on the TVB/TMA-producing microflora of cod fillets

Cod fillets ( Gadus morhua) were packed under modified atmospheres, with four different gas compositions (60% CO 2-10% O 2-30% N 2, 60% CO 2-20% O 2-20% N 2, 60% CO 2-30% O 2-10% N 2, 60% CO 2-40% O 2), and stored at 6 °C. Plate counts were carried out after 3, 4, 5, 6 and 7 days, to follow the growth of aerobic and anaerobic bacteria, lactic acid bacteria, H 2S-producing bacteria and Enterobacteriaceae. The production of total volatile bases (TVB) and trimethylamine (TMA), and the changes in pH of the fillets were measured. Modified atmosphere packaging (MAP) had in general an inhibitory effect on the growth of the microflora but limited inhibition of the production of TVB and TMA. Despite the fact that increased oxygen proportions in the atmosphere contributed in a slightly lower production of TMA, all the samples had a TVB and TMA content high enough to be considered as spoiled after 4 days' storage at 6 °C. A total aerobic plate count at 25 °C of a 10 6 cfu g , combined with the presence of only a 10 3 cfu g of H 2S-producing bacteria, which are normally considered as TMAO-reducing organisms in fish, cannot explain the strong increase in TMA. A high cell concentration of more than 10 8 cfu g of Shewanella putrefaciens is required for production of a TMA level normally found in spoiled fish. This suggests that there could be another type of bacterium in fish, not involved in the spoilage of unpacked fish, which is resistant to 60% CO 2, is not H 2S-producing, and shows a high TMAO-reducing capacity. This bacterium could be Photobacterium phosphoreum.

Anisakis simplex Rudolphi, 1809, infection in fillets of Barents Sea cod Gadus morhua L.

The purpose of this study is to record the infections of the whaleworm ( Anisakis simplex) in fillets of Norwegian Arctic cod from coastal and oceanic waters of the Barents Sea. The percentage of cod infected was 96%. The mean intensity of A. simplex in fillets of oceanic and coastal cod was 4.3 and 6.1 respectively. These values were significantly different. Comparison with previous work indicates that the A. simplex infection in Barents Sea cod is little influenced by the large fluctuations in the abundance and distribution of the main fish stocks (i.e. capelin, herring and cod) in this ecosystem. It is not clear which factors are responsible for the maintenance of the high prevalences of Anisakis in the Barents Sea.

Storage Quality of Fresh and Frozen‐thawed Fish in Ice

ABSTRACTThe objective was to determine whether traditional quality indexes of fresh (unfrozen) fish like sensory analysis, bacterial counts and trimethylamine content could be applied to thawed whole cod, cod fillets and ocean perch fillets kept in ice. Freezing and short‐term freezer storage (≤5 wk at −25°C) had very little effect on bacterial counts. During long‐term freezer storage (≥14 wk at −25°C) total counts were reduced as well as counts of trimethylamine oxide‐reducing bacteria in cod fillets but not in ocean perch fillets. When the thawed fish was unacceptable the trimethylamine was <1 mgN/100g. Trimethylamine as a spoilage indicator was of no value when evaluating spoilage of thawed whole cod, cod fillets and ocean perch fillets kept in ice.

Evaluation of a predictive model for the shelf life of cod ( Gadus morhua) fillets stored in two different atmospheres at varying temperatures

• The shelf life of fish and food in general is difficult to predict especially if stored at varying temperatures. Shelf life models were constructed (Einarsson, 1992) for cod fillets stored at constant temperatures. The aim of this study was to evaluate if these models could be used to predict spoilage and bacterial growth in cod fillets stored in air and modified atmosphere at constant and varying temperatures. • Fresh fillets were packed and stored at constant or varying temperatures between −2°C and 5°C. Samples were taken at regular intervals for bacteriological and sensory evaluation. The results showed that fish stored at + 0.6°C in air had a shelf life (assessed by sensory analysis) of 11 days which is close to what could be expected and predicted. The increase in bacterial number observed was generally less than predicted. For fish fillets, stored in air at +5°C for 3 days, then at + 0.6°C for 3 days and finally at −2°C, the shelf life was found to be 7 days which was in good agreement with the predicted shelf life. The shelf life of fillets stored at same the temperatures in modified atmosphere was found to be 9 days but by prediction 11 to 12 days. The models for predicting changes in sensory score were more accurate than those predicting changes in bacterial numbers.

Antibacterial potential of Enterococcus faecium strains isolated from sous-vide cooked fish fillets

Nineteen isolates of Enterococcus faecium were isolated from sous-vide cooked cod fillets stored 3-8 weeks at 3°C. Fourteen isolates produced proteinaceous substances inhibitory to different strains of Listeria monocytogenes, other pathogenic bacteria and spoilage bacteria. The isolates had similar growth profiles in broth at 0, 3, and 5°C. In the presence of 10 7 cfu ml -1 E. faecium, L. monocytogenes (10 2 cfu ml -1) was strongly inhibited at 3°C and partially at 5°C and 15°C. When cultivated with 10 4 cfu ml -1 E. faecium, L. monocytogenes (10 2 cfu ml -1) was only slightly inhibited at 15°C and not at 3°C or 5°C. Spontaneous resistance phenomena were observed at 15°C after 11 days. The isolates of E. faecium did not produce off-odours in shrimp extracts or sous-vide cooked fish. The potential use of the isolated strains of E. faecium as biopreservation is suggested.

Survey of Listeria monocytogenes in New Zealand Seafood

A Survey was carried out on oysters and mussels collected from three different areas of New Zealand for the presence of Listeria monocytogenes and fecal coliforms. Three samples of oysters contained L. monocytogenes. Fifty-two samples of processed seafood purchased from retail outlets were tested for L. monocytogenes before their designated use-by dates. Eighteen samples (35%) contained L. monocytogenes. These were cold-smoked salmon, hot-smokes squid strips, cold smoked blue cod fillet, smoked eel fillets and hot-smoked mussel samples. It was concluded that contamination of the processed seafood occurred during processing rather than form the aquaculture sites.