Tag: Superchilling

Peer-reviewed articles

Impact of onboard chitosan treatment of whole cod (Gadus morhua) on the shelf life and spoilage bacteria of loins stored superchilled under different atmospheres

Contact

Pauline Bergsten

Ph.D. Student

paulineb@matis.is

The initial handling of marine fish on board fishing vessels is crucial to retain freshness and ensure an extended shelf life of the resulting fresh products. Here the effect of onboard chitosan treatment of whole, gutted Atlantic cod (Gadus morhua) was studied by evaluating the quality and shelf life of loins processed six days post-catch and packaged in air or modified atmosphere (% CO2/ O2/ N2: 55/5/40) and stored superchilled for 11 and 16 days, respectively. Sensory evaluation did not reveal a clear effect of chitosan treatment on sensory characteristics, length of freshness period or shelf life of loins under either packaging conditions throughout the storage period. However, directly after loin processing, microbiological analysis of loins showed that onboard chitosan treatment led to significantly lower total viable counts as well as lower counts of specific spoilage organisms (SSO), such as H2S-producers and Pseudomonas spp., compared to the untreated group. In addition, the culture-independent approach revealed a lower bacterial diversity in the chitosan-treated groups compared to the untreated groups, independently of packaging method. Partial 16S rRNA gene sequences belonging to Photobacterium dominated all sample groups, indicating that this genus was likely the main contributor to the spoilage process.

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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

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

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

Effect of cooling and packaging methods on the quality deterioration of redfish fillets

Published:

01/09/2011

Authors:

Hélène L. Lauzon, Aðalheiður Ólafsdóttir, Magnea G. Karlsdóttir, Eyjólfur Reynisson, Björn Margeirsson, Sigurjón Arason, Emilía Martinsdóttir

Supported by:

EU IP Chill ‐ on (contract FP6‐016333‐2)

Contact

Aðalheiður Ólafsdóttir

Sensory evaluation manager

adalheiduro@matis.is

Effect of cooling and packaging methods on the quality deterioration of redfish fillets

The aim of the experiment was to evaluate the effect of slush ice cooling after filleting and / or packing in vacuum packaging on the deterioration of the quality of fresh redfish fillets. The fillets were stored at -1 ° C for 6 days to simulate well-executed sea transport in foam plastic boxes and then at 2 ° C, as happens after delivery abroad and storage in retail. Product and ambient temperature were monitored from packaging and sensory evaluation, microbial and chemical measurements were performed. The fish was caught in the spring and processed 6 days after fishing. The results show that the quality of the raw material was not the best during packaging as the development process (PV and TBARS) was well underway. This probably explains why none of these refrigeration methods led to an increase in shelf life. It was also found that there was no benefit in cooling the fillets unprotected in slush ice as the microbial growth and formation of TVB-N and TMA in the fillets was faster with further storage. However, it seems preferable to refrigerate vacuum packed fillets in ice cream as this method has led to slower growth of pest microorganisms, lower TMA levels and a slower development process. Photobacterium phosphoreum is important in the process of damaging fresh redfish fillets, regardless of the packaging method.

The aim of this study was to evaluate the effect of slurry ice cooling in process (post ‐ filleting) and packaging method (+/‐ oxygen) on the quality deterioration of skinned redfish fillets during storage in expanded polystyrene boxes simulating well ‐ performed sea freight transportation (6 days at ‐1 ° C) followed by storage at the retailer (2 ° C). Also, to assess the use of vacuum ‐ packaging to protect the fillets from direct contact with the cooling medium (slurry ice) and to achieve superchilling following extended treatment. Temperature monitoring as well as sensory, chemical and microbial analyzes were performed. The fish was caught in the spring and processed 6 days post catch. The results show that quality of the fillets was not optimal at packaging, due to the detection of primary and secondary oxidation products. This may have been the reason why shelf life extension was not achieved by any of the methods evaluated. Further, there was no advantage of cooling the fillets unpacked since this method stimulated microbial growth and formation of basic amines. On the other hand, slurry ice cooling of vacuum ‐ packaged fillets led to a slower microbial development, the lowest TMA level and delayed autoxidation. Finally, the importance of Photobacterium phosphoreum in the spoilage process of redfish fillets, independently of the packaging method, was demonstrated.

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Reports

Effect of temperature control on the efficiency of modified atmosphere packaging of cod loins in bulk

Published:

01/06/2011

Authors:

Hélène L. Lauzon, Kolbrún Sveinsdóttir, Magnea G. Karlsdóttir, Eyjólfur Reynisson, Björn Margeirsson, Emilia Martinsdóttir

Supported by:

EU IP Chill ‐ on (contract FP6‐016333‐2)

Contact

Kolbrún Sveinsdóttir

Project Manager

kolbrun.sveinsdottir@matis.is

Effect of temperature control on the efficiency of modified atmosphere packaging of cod loins in bulk

The aim of the experiment was to compare the freshness, quality and shelf life of sub-chilled (CBC) cod necks in air storage and in aerated packages (MAP) at controlled temperatures to simulate temperature fluctuations during transport and distribution in the European market. Changes in the composition of the gas in the packages were monitored and sensory assessments and microbial and chemical measurements were performed. The fish was caught in bottom trawls in the spring and processed three days after fishing. There was a two-day prolongation during the freshness period and one day for the shelf life of fish in aerated packages (2.7 kg in a tray) compared to air (3.1 kg) in foam plastic, despite a 0.5 ° C difference in the average temperature of the groups and the air group was stored at lower temperatures (‐0.3 ± 0.9 ° C). The greatest temperature fluctuations led to the greatest shortening of the freshness time in air-conditioned packages. Cod saddles stored subcooled at -1.1 ± 0.1 ° C had a shelf life of 13 days. The results of microbial counts and chemical measurements showed the importance of Photobacterium phosphoreum in the formation of TMA in the process of damaging cod necks during both air and air exchange packaging. MAP and subcooling slowed down and changed the damage process. MAP increased drip by 2% in the later stages of storage.

The aim of this study was to compare freshness, quality deterioration and shelf life of CBC (combined blast and contact) ‐treated cod loins packaged in bulk under different atmospheres (air or modified atmosphere, MA) and stored under different temperature profiles to mimic temperature changes during transport and distribution to European markets. Sensory, chemical, microbial and headspace gas composition analyzes were performed regularly. The fish was caught by trawler in the spring and processed 3 days post catch. Following simulation of current sea freight conditions and distribution to European markets, a 2 ‐ day and 1 ‐ day increase in freshness period and shelf life of MA ‐ packaged fish (2.7 kg in trays), respectively, was observed compared to air ‐ stored loins (3.1 kg in EPS boxes). This is despite a mean product temperature difference of 0.5 ° C between the products, being lower (‐0.3 ± 0.9 ° C) for air ‐ stored fish. Abusive conditions had the greatest impact on the reduction of the freshness period for MAP fish. Superchilled storage of MAP loins (‐1.1 ± 0.1 ° C) resulted in a 13 ‐ day shelf life. Evaluation of microbial and chemical indicators emphasized the importance of Photobacterium phosphoreum and TMA formation in the deterioration of cod loins stored in air or MA, while superchilled MAP storage delayed as well as modified the spoilage pattern. MAP increased drip loss by about 2% at late storage.

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Reports

Functionality testing of selected Chill ‐ on technologies during a transport ‐ simulation study of palletized cod boxes: qPCR for fish spoilage bacteria, SLP model and QMRA to evaluate pathogen growth in spiked cod

Published:

01/11/2010

Authors:

Hélène L. Lauzon, Björn Margeirsson, Kolbrún Sveinsdóttir, Eyjólfur Reynisson, María Guðjónsdóttir, Emilia Martinsdóttir (Matís); Radovan Gospavic, Nasimul Haque, Viktor Popov (WIT); Guðrún Ólafsdóttir, Tómas Hafliðason, Einir Guðlaugsson, Sigurður Bogason (UoI)

Supported by:

EU IP Chill ‐ on (contract FP6‐016333‐2)

Contact

Kolbrún Sveinsdóttir

Project Manager

kolbrun.sveinsdottir@matis.is

Functionality testing of selected Chill ‐ on technologies during a transport ‐ simulation study of palletized cod boxes: qPCR for fish spoilage bacteria, SLP model and QMRA to evaluate pathogen growth in spiked cod

In this study, tests were carried out on technical solutions developed in the EU project Chill ‐ on, where a simulation experiment was set up to simulate the actual transport of fish from Iceland to Europe. The temperature fluctuations experienced by the fish were aimed at mimicking transport from Iceland to France by ship. Pallets of cod fillets in foam plastic boxes were transported to the Westman Islands by ship and back to Matís in Reykjavík. Samples from these pallets were then compared with control samples that had been stored in Matís' refrigerated conditions. Cod nuggets were also packed in consumer packs (trays) immediately after processing and then after 6 days and were stored in subcooled or refrigerated conditions. Microbial growth experiments were also performed in which Listeria monocytogenes, Escherichia coli and Salmonella Dublin were added to cod necks stored in foam boxes in conditions similar to the storage and transport processes during export. Temperature measurements, sensory evaluation, microbial and chemical measurements were used to present data to test and verify the QMRA / SLP models and quantification of Pseudomonas bacteria using qPCR technology.

The aim of the cod wet trials and the corresponding shelf life study was to include scenarios to test and demonstrate the functionality of some Chill ‐ on technologies in a simulated cod supply chain. Temperature fluctuations were induced according to the actual scenario in the supply chain of cod from Iceland to France via sea freight. The study included sample groups created at the point of processing after packaging in EPS boxes. The reference group was stored at Matís under superchilled conditions. Simulation trials for downward distribution were performed at Matís upon receipt of the pallets shipped to the Westman Isles from Reykjavik (Iceland ‐ Europe freight simulation) and compared with the reference group. Repackaging of loins in retail trays was performed on days 0 and 6 with storage under superchilled and chilled conditions, respectively. In addition, a pathogen challenge trial was performed by spiking loins (5 kg) with Listeria monocytogenes, Escherichia coli and Salmonella Dublin, followed by storage in EPS boxes under temperature conditions simulating export and distribution. Temperature recordings along with microbial, chemical and sensory analyzes from the groups evaluated provided necessary data to test and validate the QMRA / SLP models and the quantitative molecular (qPCR) method to estimate counts of pseudomonads.

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Reports

Overview on fish quality research - Impact of fish handling, processing, storage and logistics on fish quality deterioration

Published:

01/11/2010

Authors:

Hélène L. Lauzon, Björn Margeirsson, Kolbrún Sveinsdóttir, María Guðjónsdóttir, Magnea G. Karlsdóttir, Emilia Martinsdóttir

Supported by:

AVS R&D Fund of Ministry of Fisheries in Iceland, Technology Development Fund and EU IP Chill-on (contract FP6-016333-2)

Contact

Kolbrún Sveinsdóttir

Project Manager

kolbrun.sveinsdottir@matis.is

Overview on fish quality research - Impact of fish handling, processing, storage and logistics on fish quality deterioration

The short shelf life of fish is a limiting factor in the export of fresh fish products from Iceland. The initial quality of raw materials, methods of cooling, processing, packaging and conditions during storage and transport are discussed, as well as the effects of all these factors on the freshness and shelf life of fish products. Temperature control is very important to maintain the quality of the fish. Pre-processed fillets have been used to lower the pre-packing temperature. However, care must be taken that the pre-cooling technology does not endanger the microbial condition of the product and thus causes it to be damaged earlier after packaging. The synergistic effects of supercooling and aerated packaging (MAP) can significantly extend the freshness period and shelf life of fish products. Furthermore, packaging methods are examined, including new, more environmentally friendly packaging. Finally, the effect of transport routes of fresh fish products on their final quality to consumers in the market is discussed. This report provides an overview of the research of the Fisheries Research Institute and Matís ohf over the past three decades on the subject. Furthermore, it is discussed how these results can benefit the fishing industry.

The limited shelf life of fresh fish products is a large hurdle for the export of fresh products from Iceland. The influence of raw material quality, cooling methods, processing, packaging and storage conditions on freshness and shelf life extension is discussed. Temperature control is important to maintain fish quality. Pre-cooling of fillets in process has been used to lower the temperature prior to packaging. However, the cooling technique applied should not compromise the microbiological quality of the product and render it vulnerable to faster spoilage postpackaging. Synergism of combined superchilling and modified atmosphere packaging (MAP) can lead to a considerable extension of the freshness period and shelf life of fish products. Further, alternative and environmentally-friendly packaging methods are considered. Finally, the impact of transportation mode of fresh fish products on their resulting quality is examined. This report provides an overview of the findings on fish research carried out at Matís (Icelandic Fisheries Laboratories) over the last three decades and further discusses their practicality for the fish processing industry.

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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

Research 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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