Reports

The effect of mortality on fish quality ll

Published:

15/08/2019

Authors:

Gunnar Þórðarson, Sigurjón Arason

Supported by:

AVS Fisheries Research Fund (R 17 019-17)

contact

Gunnar Þórðarson

Regional Manager

gunnar.thordarson@matis.is

The effect of mortality on fish quality ll

The purpose of the study was, on the one hand, to investigate the effect of supercooling on the death-hardening process of cod and salmon fillets and to compare with conventional cooling; and, on the other hand, to examine whether filleting at different times in the death solidification process (before mortality, in mortality and after the process ends) had a product quality. For salmon, a preliminary experiment was performed on which the main experiment was based, while in cod an experiment was performed on wild cod and farmed fish.

Supercooling of cod is based on cooling down to -0.8 ° C and salmon at -1.2 ° C, while conventional cooling is based on 0 ° C for both species. Differences between groups were examined and also differences within groups were compared. Small differences within groups indicate a more accurate and credible conclusion.

The results of a survey carried out by a sensory evaluation team show that the effect of supercooling is considerable as there is less contraction in the death solidification process, and the effect on quality is therefore smaller. There is a difference between wild cod and farmed cod, as it is known that the water content between cells is less in farmed development than wild. It might be interesting to look at the difference between farmed salmon and wild salmon, but that was outside the scope of this study.

It can be concluded that with supercooling it would be possible to process salmon for freezing to death without degrading quality, which could be important in the marketing of fresh products in the future, as the salmon could be processed immediately at slaughter and thus increase shelf life in foreign markets.

One of the aims of the project was to prepare promotional material on the death solidification process and its impact on the quality of products for salmon and cod producers in Iceland, which could benefit them in the future in tackling new challenges in the production of high-quality products.

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Reports

The effects of food container depth and coverage on the quality of superchilled rainbow trout

Published:

01/09/2018

Authors:

Magnea Karlsdóttir, Erwan Queguiner, Björn Margeirsson, Sigurjón Arason, Aðalheiður Ólafsdóttir

Supported by:

AVS R&D Fund (R 17 016-17), Technology Development Fund (164698-1061)

contact

Sigurjón Arason

Chief Engineer

sigurjon.arason@matis.is

The effects of food container depth and coverage on the quality of superchilled rainbow trout

Fresh farmed fish is generally gutted and packed in a foam plastic box with ice for export in refrigerated containers. In view of the great development that has taken place in terms of supercooling and its positive effect on the quality of fish products, other more cost-effective and environmentally friendly packaging solutions have been examined, including insulated food containers. The main objective of the project was to evaluate the impact of different packaging methods on the quality of fresh rainbow trout. Gutted fish with a head was packed in a foam plastic box and insulated pots of different depths (29-60 cm). In addition to comparing different depths of pots, different embodiments of closing pots were also examined. Experimental fish were observed at the top and bottom of each tank. The pots were stored in a temperature-controlled environment at about -1 ° C and measurements were made after 8 and 13 days after packing. The fish packed in a foam box was either supercooled before packing or cooled in the traditional way with ice. This was done to assess the effect of supercooling on fresh rainbow trout. To assess the quality of the rainbow trout, microbial growth, texture and release in fillets were monitored. The results showed that the packaging solutions examined in the project had a relatively small effect on the total number of microorganisms, but there was no significant difference between experimental groups at the end of the storage period. In general, there was little to no difference between groups in texture and texture in fillets. On the other hand, the results showed that it is necessary to close the pots, but the type did not have a significant effect. Supercooling before packing had a significant effect on release. Fish that was cooled in the traditional way and packed in a foam plastic box with ice had significantly more release compared to when it was super-cooled and packed in a pot or foam plastic box without ice. The results show that there is no significant difference between foam boxes and pots of different depths compared to the quality variables examined in this project. They indicate that the transport of supercooled rainbow trout in pots is a viable option in terms of the stability of the raw material and the quality of the product.

The overall aim of the study was to explore the effects of different packaging solutions on the quality of fresh rainbow trout. Different packaging methods included expanded polystyrene boxes (EPS), insulated food containers of 29 to 60 cm depth with various combination of covers. Each container was split up into two groups, top- and bottom layer. Both fish chilled on ice and superchilled fish were considered. Microbial growth and sensory characteristics (fillet gaping, softness and elasticity) were used to evaluate the quality of the rainbow trout fillets after 8 and 13 days of storage at around -1 ° C. The different packaging solutions had no effects on the microbial quality of the fish. Moreover, no listeria activity was detected. Sensory evaluation showed minor differences between containers of different depths and / or EPS boxes, as well as between top and bottom layers. However, the presence of cover proved to be of great importance, but the type of cover turned out to be not relevant. The effects of superchilling before packaging on fillet gaping was evident in present study since fish packed in EPS box with ice resulted in more gaping than superchilled fish packed in EPS boxes and / or containers without ice.

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Reports

The effects of food container depth on the quality and yield of superchilled and iced Atlantic salmon

Published:

01/09/2018

Authors:

Rúnar Ingi Tryggvason, Magnea Karlsdóttir, Björn Margeirsson, Aðalheiður Ólafsdóttir, Sigurjón Arason

Supported by:

AVS R&D Fund (R 17 016-17), Technology Development Fund (164698-1061), The Icelandic Student Innovation Fund (185693- 0091)

contact

Aðalheiður Ólafsdóttir

Sensory evaluation manager

adalheiduro@matis.is

The effects of food container depth on the quality and yield of superchilled and iced Atlantic salmon

The aim of the project was to compare the quality of farmed salmon, which was frozen and supercooled, and stored in different packaging solutions. Different insulated pots (32, 42 and 60 cm deep) and EPS boxes were used to transport and store the farmed salmon. Quality was examined after 4, 10 and 14 days of storage in supercooled conditions, where water loss, texture, boiling efficiency and sensory evaluation factors were assessed. Water loss on supercooled salmon was significantly more in deeper packaging compared to shallower packaging after 10 to 14 days of storage at -1 ° C. Frozen salmon stored in EPS lost less water than supercooled salmon in EPS, probably due to inaccurate temperature control during supercooling. Sensory evaluation, texture measurements and boiling efficiency showed little difference between salmon stored in different depths of packaging. Icebergs were more visible in frozen salmon stored in deep pots compared to EPS boxes. Discharge was more visible in frozen salmon compared to super-chilled salmon. The results do not exclude the use of deep tanks for the transport and storage of fresh salmon, but do not specify the maximum size of packaging. The size and volume utilization of packaging affects water loss and transport costs. Supercooling can have many benefits for manufacturers and consumers, but it is necessary to have good control of the supercooling to ensure its effectiveness.

The aim of the study was to compare quality differences of farmed Atlantic salmon, both iced and superchilled, that was stored in different sized packaging solutions. Different sized insulated containers (32, 42 and 60 cm deep) as well as EPS boxes were used to transport and store the fish. The quality was evaluated after 4, 10 and 14 days of storage, where drip loss, texture, cooking yield and sensory evaluation were performed. Increased container depth significantly increased the drip loss of superchilled salmon during 10 to 14 days storage at -1 ° C. Iced storage of salmon in EPS resulted in less drip loss compared to superchilled salmon stored in EPS, most likely due to uncontrolled superchilling conditions. Sensory evaluation, texture analysis and cooking yield did not reveal any major differences between salmon stored in containers of different depths. In case of iced salmon, pressure marks were more prominent with increased depth of containers. Gap was more noticeable in iced salmon compared to superchilled salmon. The results did not rule out the use of large insulated containers, but they do not specify the maximum recommended depth of containers intended for salmon packaging. The size and volume of packaging containers affect drip loss as well as transportation costs. Superchilling of fresh foods can have many benefits for producers and consumers but a controlled and optimized superchilling process is needed to ensure its effectiveness.

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Reports

New technology to increase the value of catfish catches

Published:

01/07/2018

Authors:

Gunnar Þórðarson, Sigurjón Arason

Supported by:

AVS Fisheries Research Fund (R 025-11), Rannís

contact

Gunnar Þórðarson

Regional Manager

gunnar.thordarson@matis.is

New technology to increase the value of catfish catches

The purpose of the project was to adapt processing to supercooled raw materials, to ensure the homogeneity of raw materials with the aim of improving product quality, increasing utilization and minimizing fillet defects. In the project, a new type of skinning machine was developed and then tested under real conditions. Comparison of supercooled and traditional (frozen) ingredients. Supercooled raw material is stiffer than conventional, and the same can be said for fillets cooled after filleting to ensure packing in fresh packages at low temperatures, preferably below 0 ° C. Traditional skinning machines have not been able to handle such raw material, but the new machine has already been put into use and is proving successful. A comparative experiment was carried out between super-chilled haddock that was six days old and traditional raw material from the same catch. Subsequently, a comparative study was conducted on cod, made from super-chilled and conventional raw materials. Utilization, fillet quality and defects were compared, as well as product division after cutting into fillet pieces, as well as temperature processes during processing in both groups. The results were very good for supercooled raw materials, both in terms of quality, utilization and temperature of products.

The purpose of the project was to customize processing of sub-chilled raw materials to ensure uniformity of raw materials with the aim of improving product quality, increasing utilization and minimizing fillet defects. A new skinning machine for demersal fish was designed and tested in this project, especially to work with sub-chilled raw material. Sub-chilled raw material is more rigid than traditional raw material and can withstand more handling and give better quality of the finished product. Sub-chilled raw material also provides lower product temperature in packed fresh fish production, at 0 ° C or even below it. Traditional skinning machines have not been able to handle sub-chilled fillets. A comparative experiment with six-day old haddock where sub-chilled raw material were compared with traditional one, from same catch, were processed. Built on that outcome a follow-up, a comparative study of cod was processed with sub-chilled and traditional raw material. In both experiments a comparison of yield, fillets quality, fillets defects and temperature throughout the production into final packaging were recorded. The results were excellent in favor of sub-chilled raw material, both in terms of quality, yield and temperature of products.

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Reports

Sub chilling of fish

Published:

17/07/2017

Authors:

Gunnar Þórðarson, Sigurjón Arason, Magnea Karlsdóttir

Supported by:

Technology Development Fund

contact

Gunnar Þórðarson

Regional Manager

gunnar.thordarson@matis.is

Sub chilling of fish

The aim of the project was to utilize the knowledge of supercooling of fish that has been developed in laboratories in recent decades; industrialize the concept and develop methods and equipment to control the cooling. It is important to cool the raw material below the freezing point or just below the temperature at which the first ice crystals form in the fish species in question, fast enough so that large crystals do not form in the muscles and cause cell damage. It is important to control the cooling correctly as well as to maintain a supercooled condition during storage and transport, but fluctuations in temperature can cause quality deterioration. The results of research show that ice-free transport and storage of super-chilled fish is a realistic solution that reduces the cost of fishing and processing as well as reducing the cost of transport and significantly reducing the footprint of fresh fish production. Fresh salmon has been transported ice-free but super-chilled for shorter and longer distances and stored for a week before processing with excellent results. In connection with the project, supercooling has been used on a large scale in Sauðárkrókur, where the trawler Málmey SK 1 has landed over 15 thousand tonnes in the past two years of supercooled catch and thus not used ice on board or for storage for production in fish processing.

The project objective was to utilize knowledge of sub chilling of fish developed in laboratories for the past decades; and to industrialize the concept and to develop methods and means for centralizing the process. The control of the chilling process is important, to chill raw material sufficiently without freeze out more than 20% of its water and without developing large ice crystals in the muscles. It is also important to keep storage temperature under control and stable and for the same reason temperature fluctuation can cause growth of ice crystals in the muscle. Based on results obtained in present project it can be concluded that sub chilling provides opportunities to use ice-free value chain for fresh fish, lowering cost of production, logistic and considerably the carbon footprint for the final products. Fresh salmon without any external refrigerant (ice) has been transported for long distance, by trucks and airplanes, and stored for long time with acceptable results. The trawler used in this project has landed over 15 thousand tonnes of sub chilled fish for the last two years without using any ice for chilling and storage. The fish is stored in the fish plant and processed without using any ice preservation.

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Reports

The effect of rigor mortis on fillet quality

Published:

01/10/2016

Authors:

Gunnar Þórðarson, Albert Högnason, Anton Helgi Guðjónsson

Supported by:

AVS Fisheries Research Fund (R 16 014-16)

contact

Gunnar Þórðarson

Regional Manager

gunnar.thordarson@matis.is

The effect of rigor mortis on fillet quality

The purpose of the study was, on the one hand, to investigate the effects of supercooling on freezing and comparing it to conventional refrigeration, and on the other hand to prepare promotional material that could be used to introduce stakeholders in the fisheries sector to the importance of controlling the freezing process. A study was carried out on cod and salmon and it was carried out at two different seasons for cod, but there can be great differences in the condition of the raw material depending on when and where the fish is caught. The study was twofold in that, on the one hand, data were obtained on the effect of cooling on the death solidification process, where the groups were compared; supercooled and traditional, and on the other hand to interpret the results for promotional material. Supercooling in cod is based on cooling down to -0.8 ° C and salmon at -1.5 ° C, while conventional cooling is based on 0 ° C for both species. Differences between groups were examined as well as comparing differences within groups. Small differences within groups indicate a more accurate and credible conclusion. The results show that there is a large difference in the contraction of the fish muscle when it goes through the freezing process, depending on whether it is supercooled or conventional cooling is used. It can be concluded that there is a great quality benefit in the use of supercooling for death stiffness, which reduces contraction and consequently reduces tension between muscles and spine. With too fast and too much contraction of the death stiffness, the muscle can easily be damaged, such as loosening, the stiffness of the fillets decreases, etc.

The purpose of this project was to study the effect of superchilling on rigor mortis process and compare it to traditional chilling with ice. Also to prepare promotional material to enlighten the fishery industry on the importance of managing the process of rigor mortis for product quality. A study was conducted on cod and salmon, including seasonality effect on rigor mortis for cod. The definition on sub chilling in this study is; for cod it is based on cooling to -0.7 ° C and for salmon down to -1.5 ° C and for traditional chilling by ice is targeted at 0 ° C for both species. The rigor process was studied between groups, sub-chilled and traditional, and within groups to investigate standard deviation between samples to sample credibility of outcome. The results indicate a large difference in the contraction process on whether the fish is super chilled or traditional cooling used. The conclusion of the study indicates that sub chilling, which reduces the contraction and consequently the tension between muscle and backbone in the process, can have a large effect on fillet quality, less gaping and a firmer product.

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Reports

Sub-chilling of salmon

Published:

01/12/2015

Authors:

Gunnar Thordarson, Magnea Karlsdottir, Roger Pedersen, Magnus Johannsson, Albert Hognason

Supported by:

Norwegian Research Council

contact

Gunnar Þórðarson

Regional Manager

gunnar.thordarson@matis.is

Sub-chilling of salmon

The aim of the project was to increase the quality of fresh salmon production, by improving the cooling chain during production and transport. By using supercooling methods, salmon producers will be able to reduce their production costs due to lower transport costs and at the same time improve the quality of production. The salmon was cooled to -1.5 ° C which increased the lifespan and quality of the product. In addition to improving production during slaughter, gutting and packaging, supercooling can also create opportunities for further processing; filleting, smoking, chopping, etc. to improve their production through increased utilization and value along with happier customers. Among other things, supercooling makes it possible to transport the refrigerant into the fish flesh instead of using ice for transport. The project compared the cooling chain of super-chilled salmon with conventional. The former was transported without ice but the traditional one with ice, for further processing in Finland and Norway. Such a comparison was also made between super-chilled and traditional salmon that was transported to Iceland via Oslo on the one hand and to Tokyo via Oslo on the other. The results give rise to optimism about the use of supercooling in the salmon transport chain, both to reduce transport costs and to ensure product quality.

The ultimate goals of the project was to increase quality of fresh salmon products, provide a more secure cold chain of fresh product, and lower production and logistic costs. Having the fish in a sub-chilled state throughout the production, will give Grieg Seafood several quality advantage including firmer raw material and lower bacteria and enzyme activity in the fresh fish. Fish was packed in a sub-chilled state of -1.5 ° C, hence extending shelf-life and quality. This will have several advantages for the primary producer, resulting in products with higher yield and more value, and in products of higher quality for their customer of secondary processing. Secondary processors will have better control of the product logistic and extended time for selling fresh product with longer shelf-life. Using the sub-chilling method, no ice will be needed during logistic, saving enormous transportation costs, especially in airfreight. Comparison between the cold-chain of sub-chilled and traditional produced salmon was executed in this project, with the former transported without additional ice. The salmon was trucked from Simanes to a secondary processors in Finland and Denmark with excellent result. The two groups were also flown to Iceland, via Oslo, and also to Tokyo via truck to Oslo. The result of this comparisons demonstrates that the sub-chilling method could be used to minimize transportation cost and secure the product quality during logistics.

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Reports

Research of superchilling of whitefish / Research of superchilling of whitefish

Published:

01/10/2014

Authors:

Gunnar Þórðarson, Albert Högnason, Hólmfríður Sveinsdóttir

Supported by:

Westfjords Growth Agreement

contact

Gunnar Þórðarson

Regional Manager

gunnar.thordarson@matis.is

Research of superchilling of whitefish / Research of superchilling of whitefish

Five studies were conducted by a research team (supercooling team) in the summer of 2014 to test the effect of supercooling on the processing and product quality of whitefish. This project was based on foreign scientific research on supercooling, which was carried out in laboratories, while the research of the supercooling team was carried out under processing conditions. The results of the research team indicate even more activity than the basic research on which it was based. The main drawbacks were that with supercooling immediately after bleeding and gutting, death stiffness can be significantly delayed, but no damage processes begin until it is completed. It is known that the main reasons for release are rapid death stiffness as the flesh tears with a rapid contraction that clashes with the fish's bone marrow. Fish is 800 times more sensitive than meat and therefore it can withstand very little damage during handling. The results of the supercooling team's research show that during supercooling, the flesh hardens without freezing and withstands all treatments much better, such as filleting, peeling and trimming. Not only is there a difference in the appearance of super-chilled fillets compared to traditional ones, but the proportion of those who went for the most expensive packages was significantly higher. An experiment was carried out at Íslandssaga in Suðureyri and the result was that the increased value due to supercooling was around ISK 900,000 per day. When processing super-chilled fillets for fresh fish export, they were returned in packages at -0.8 ° C while traditional processing was at +2 to + 5 ° C. Freezing part of water in fillets (5‐30%) builds up a high cooling energy that maintains a low temperature throughout the processing (filleting, skinning and trimming). The results of the research team are that with supercooling on board a fishing vessel down to -1 ° C immediately after bleeding and gutting, the use of ice becomes unnecessary for storage in trains and warehouses on land. Trains and cold rooms will be operated at 11 ° C, which is sufficient to maintain supercooling for a long time. Attempts were made to store cod under these conditions for eight days, and the results of research showed that its quality during processing at Fisk Seafood was high and better than with traditional processing.

Five studies were conducted by a research team (superchill ‐ team) in the summer of 2014 to test the effects of superchilling on production and quality of whitefish. This project was based on published studies on superchilling, conducted in laboratories, but the superchill ‐ team conducted their study at industrialized conditions. Conclusion of the research team suggests greater functionality than the scientific researches it was based on. The main conclusion are that super ‐ chilling right after bleeding and gutting can significantly delay rigor mortis, but no spoilage take place before that process. It is well known that the main reasons for gaping in fish fillets are the contraction and relics causing by rigor mortis. Fish is 800 times more sensitive than meat, so it is perishables against handling in processing lines, like filleting, skinning and trimming. One finding in these research is that by super chilling the fish before the process, the flesh is more stiff without being frozen, and can withstand handling in processing much better. The super chilled product is not only looking better compared to the traditional product, but the proportion of more valuable products were significantly higher. A research made in the freezing plant Icelandic Saga in Sudureyri, gave a result were increased value due to super cooling was about 900 thousand ISK per day. In the same trial a temperature for fresh packed fillets for the British market, the product temp for super chill were ‐0,8 ° C, but the traditional product were packed at +2 to +5 ° C. Freezing part of the water content of the fish, around 5‐30%, builds up a massive cooling energy that keeps low temperatures throughout the processing (filleting, skinning and trimming). Results of the research team were thatsuper ‐ cooling fish on board a fishing vessel, down to ‐1 ° C immediately after bleeding and gutting make the use of ice in fish hold redundant. The fish hold need to be run at ‐1 ° C which is sufficient to maintain the super ‐ cooling for a long time. The research team kept whole cod without ice for eight daysin container and ‐1 ° C, with demanding result and extremely good product quality, significantly better than the traditional process.

Report closed until 01.11.2016

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Reports

Comparison of wild and farmed cod muscle characteristics

Published:

01/12/2008

Authors:

Valur Norðri Gunnlaugsson, Guðrún Anna Finnbogadóttir, María Guðjónsdóttir, Kolbrún Sveinsdóttir, Hannes Magnússon, Kristján Jóakimsson, Kristín Anna Þórarinsdóttir, Sigurjón Arason

Supported by:

AVS R26-06 / AVS R&D Fund of Ministry of Fisheries in Iceland

contact

Valur Norðri Gunnlaugsson

Group Leader

valur.n.gunnlaugsson@matis.is

Comparison of wild and farmed cod muscle characteristics

The aim of the project was to make a comparison of the properties of cod products made from wild cod before and after dead-freezing and farmed cod before dead-freezing. Also experiment with storage in sludge, ice spray on brine and supercooling (-2.4 ° C) on farmed fish to investigate how the properties of the flesh change with different treatment. Mortality stiffness had a significant effect on weight gain and salt uptake during injection and storage. The uptake of pre-rigor samples was rather low while the uptake of post-rigor wild cod was significant. The pre-rigor fish had less than 5% uptake after pickling, while the wild post-rigor had almost 9% uptake. A similar pattern was seen after injection, where the longest uptake was obtained in wild post-rigor fish or 16.5%. The salinity of most samples ranged from 0.3-0.4%. No significant difference was observed between unsalted samples. In the saline-salted groups, there was only salt uptake in wild cod that was injected after death. On the other hand, salt intake in fish injected before death was insignificant and applied to both wild and farmed cod. The water content was higher in wild cod compared to farmed cod and also spray salting led to a higher water content. Measurements from NMR measurements indicated that there was a difference in the mobility of water molecules and the possible location of water, but this can affect the water - holding properties of the muscle. The fish fillets generally performed well in traditional quality assessments, whether they were injected fillets or untreated fillets. Discharges did not increase as much during the storage period as expected, although considerable discharges were made into the pre- and wild post on the thirteenth day of storage. In previous experiments, the color of farmed fish products has been very white, despite the fact that they have become unusable. On the other hand, yellow cod products turn yellow with shelf life. The results of this experiment did not confirm this difference between farmed cod and wild cod.

There was a great difference in the sensory properties of farmed cod and wild cod after boiling, primarily in texture where wild groups were much thicker, more mushy and softer. Breeding groups had a meaty mouth effect, were more gummy and stuttering, in addition to having a sweeter taste and a much more meaty taste and smell. Storage temperature generally had the effect of producing earlier symptoms of damage in products stored at + 1 ° C compared to -2.4 ° C. The shelf life of farmed cod stored at -2.4 ° C was at least 5 days longer than that of a comparable group stored at + 1 ° C. The effect of storage temperature was also observed in the number of microorganisms, which together with the injection salting led to a larger number of microorganisms. However, there was little difference in products in terms of whether processing took place before or after death solidification. The research was part of the project "Processing and quality control of farmed cod, more specifically a summary for work components 2 and 4.

Production of farmed cod is increasing rapidly, but quality appraisals show that farmed cod has different characteristic from wild cod. These different characteristics make traditional production methods not suitable for farmed cod and therefore it is necessary to analyze those characteristics and adjust production methods especially for farmed cod. Matis ohf has been involved in farmed cod research from its foundation and the company built its foundation on the work which was done by its predecessors. The aim of this project was to look at these different characteristics between farmed and wild cod, pre and post rigor. The aim was also to do experiments with injection of brine and superchilling (-2.4 ° C) and detect the impact of different methods. NMR was used to analyze difference in longitudinal relaxation time (T1), between the samples, farmed cod had lower values for T1 than wild one. Therefore the mobility of water indicates difference in structure between the samples. High levels of glycogen are usually found in farmed cod which results in sharp fall of pH after slaughter. This low pH affects texture, because of collagen degradation which results in gap formation. The low pH also affects water holding capacity of the farmed cod. Measurements have shown higher pH in wild cod and this difference continues through low temperature storage. Texture measurements after 2 days storage indicates that farmed cod is lower in firmness than wild one, regardless of whether the fish is filleted pre- or post rigor. Sensory panels have also detected difference between wild and farmed cod. Wild cod is more tender and mushier, while the farmed one has more meaty texture, is more rubbery and has a clammy texture. Also the farmed fish has sweeter taste and more meaty taste and smell. Farmed cod is different from wild cod in many aspects. Therefore it is necessary to know those aspects and adjust processes especially for production of consumer goods from farmed cod.

Report closed until December 2011 / Report closed until December 2011

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Reports

Effect of modified atmosphere packaging (MAP) and superchilling on the shelf life of fresh cod (Gadus morhua) loins of different degrees of freshness at packaging

Published:

01/09/2008

Authors:

María Guðjónsdóttir, Hannes Magnússon, Kolbrún Sveinsdóttir, Björn Margeirsson, Hélène L. Lauzon, Eyjólfur Reynisson, Emilía Martinsdóttir

Supported by:

AVS Research Fund, Rannís Technology Development Fund

contact

Kolbrún Sveinsdóttir

Project Manager

kolbrun.sveinsdottir@matis.is

Effect of modified atmosphere packaging (MAP) and superchilling on the shelf life of fresh cod (Gadus morhua) loins of different degrees of freshness at packaging

The purpose of this experiment was to evaluate the effect of aerated packaging (MAP) and supercooling on the quality changes and shelf life of cod pieces of fresh raw material that was processed and packaged after 2 and 7 days of fishing. The experiment was carried out in collaboration with Samherji, Dalvík and Norðlenska, Akureyri in October and November 2007. The fish was stored whole in ice until packing at -0.2 ± 0.1 ° C (2 days from fishing) and -0.2 ± 0.2 ° C (7 days from fishing). The neck pieces were cut in half and then packed (350-550 g) in an airtight container. The composition of the gas mixture was as follows: 50% CO2, 5% O2 and 45% N2. Packaged cod pieces were stored in cold storage at -0.6 ± 1.4 ° C and samples were taken over a 3-week storage period and evaluated by sensory evaluation, microbial and chemical measurements. The age of the raw material during packaging had a clear effect on the sensory evaluation of the pieces. Packing after 2 days led to a prolongation of the freshness symptoms in front of storage. In addition, signs of damage appeared much later than in bites packed 7 days after fishing. The shelf life of pieces after packing on day 7 can be roughly estimated at 4-8 days, but at least 19 days in pieces packed on day 2. This short shelf life of pieces from day 7 can be explained by the development of microbial flora and the formation of volatile pesticides as well as the temperature profile of whole fish before packaging. The effect of different packing dates had a significant effect on the microflora. Thus, the total number of microorganisms was much smaller in pieces packed after 2 days than on day 7 (log 3.7 vs 5.4 / g). This difference can largely be attributed to the varying number of Photobacterium phosphoreum (Pp) in the flesh immediately after packing, but it was not detected during the previous packing on the 3rd day of the experiment (below log 1.3 / g) and on day 8 the number was only log 2.4 / g. On that day, the number of Pp was 1000x higher in pieces packed on day 7 and they were predominant throughout the storage period in this group. On day 8, the number of other pests (H2S-producing bacteria and pseudomonads) was somewhat higher (Δ log 0.6-0.7 / g) in this group compared to the group packed on day 2. These results confirm that P. phosphoreum is one of the main damaging microorganisms in gas-packed cod pieces but also in chilled, whole cod. The results of TVB-N and TMA measurements were in good agreement with microbial measurements, but especially Pp. Low Field Nuclear Magnetic Resonance (LF-NMR) technology was used to measure relaxation times in samples over the storage period. Significantly higher "relaxation times" were measured in chunks packed after 7 days of fishing than in chunks packed 2 days after fishing. It indicates greater binding of water molecules to the environment in the 7-day bites. This is in line with the generally higher water resistance and water content of those samples over the storage period. Overall, the results show the importance of using the freshest ingredients for MA packaging, thus ensuring higher quality and longer shelf life, which should result in a higher price for the product.

The aim of this study was to evaluate the effect of modified atmosphere packaging (MAP) and superchilling on the shelf life and quality changes of fresh loins prepared from Atlantic cod (Gadus morhua) of different freshness, ie processed 2 or 7 days post catch. The study was performed in cooperation with Samherji (Dalvík, Iceland) and Norðlenska (Akureyri) in October and November 2007. The average fish temperature during storage prior to processing on days 2 and 7 was -0.2 ± 0.1 ° C and -0.2 ± 0.2 ° C, respectively. Cod loins (350-550 g) were packed in trays under modified atmosphere (50% CO2 / 5% O2 / 45% N2), stored at -0.6 ± 1.4 ° C and sampled regularly over a three-week period for sensory, microbiological and chemical analyzes . The results show that the raw material freshness clearly influenced the sensory characteristics of packed loins. Processing 2 days post catch resulted in more prominent freshness sensory characteristics the first days of storage. In addition, sensory indicators of spoilage became evident much later compared to MApacked fillets from raw material processed 5 days later. The expected shelf life of the MA-packed cod loins could be roughly calculated as 4-8 days when processed 7 days post catch, but at least 19 days when the cod was processed 2 days post catch. This reduced shelf life of MAP products processed at a later stage was also explained by the temperature profile of the whole fish prior to processing, microbial development and volatile amine production observed. In fact, the day of packaging had a major effect on the microflora development, with lower total viable counts (TVC) in loins processed earlier in relation to time from catch (log 3.7 vs 5.4 / g). This difference could be linked to large variations in levels of Photobacterium phosphoreum (Pp) in the flesh at processing times, being below detection (log 1.3 / g) 2 days post catch but found to increase to log 2.4 / g in early processed loins 6 days later, in contrast to 1000-fold higher Pp levels in loins processed later. Pp was found to quickly dominate the microflora of loins processed 7 days post catch. Similarly, slightly higher levels (Δ log 0.6- 0.7 / g) of other spoilage bacteria, H2S-producing bacteria and pseudomonads, were found 8 days post catch in loins processed later. These results confirm that P. phosphoreum is one of the main spoilage organisms in cod, unprocessed as MA-processed. TVB-N and TMA production corresponded well to the microbial development, especially counts of P. phosphoreum. Low Field Nuclear Magnetic Resonance (LF-NMR) was used to measure the relaxation times of the samples during storage. The samples packed 7 days after catch showed significantly higher relaxation times than samples packed 2 days after catch. This indicates stronger bindings of the water molecules to their environment in samples packed at a later stage. This is in agreement with the generally higher water holding capacity and water content in the samples during storage. Finally, the results demonstrated that delaying processing of raw material is undesirable if it is intended to be MA-packed and sold as more valuable products.

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