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

Preliminary project for research on the genetic composition of Icelandic herring compared to other stocks in the Northeast Atlantic: Biological diversity and processing properties / A pilot study on the multidisciplinary approach for the genetic stock identification of herring in the Northeast Atlantic: Biodiversity, functional and chemical properties

Published:

01/10/2013

Authors:

Sigurlaug Skírnisdóttir, Guðbjörg Ólafsdóttir, Sarah Helyar, Christophe Pampoulie, Guðmundur J. Óskarsson, Ásbjörn Jónsson, Jan Arge Jacobsen, Aril Slotte, Hóraldur Joensen, Henrik Hauch Nielsen, Lísa Libungan, Sigurjón Arason, Sindri Sigurðsson, Sigríður Hjörleifsdóttir, Anna K. Daníelsdóttir

Supported by:

Fisheries Project Fund, AG ‐ Fisk, Faroese Fisheries Research Fund, Research Studies Fund, Student Innovation Fund

Contact

Guðbjörg Ólafsdóttir

Researcher

gudbjorg.olafsdottir@matis.is

Preliminary project for research on the genetic composition of Icelandic herring compared to other stocks in the Northeast Atlantic: Biological diversity and processing properties / A pilot study on the multidisciplinary approach for the genetic stock identification of herring in the Northeast Atlantic: Biodiversity, functional and chemical properties

The purpose of the project was to:

· Develop a genetic analysis set with 20-25 genetic markers to assess the genetic composition and stock structure of herring in the Northeast Atlantic

· Use genetic makeup, milling and other biological factors to differentiate strains

· Study the relationship between stock units and the processing properties of herring

Knowledge of herring stocks is of great importance for the sustainable utilization and management of herring fisheries. A key factor for sustainable fisheries management and quota allocation is to know what stock units are in the fishing areas and how large they are. In this project, approx. 4,500 samples collected from nine possible stock units in the Northeast Atlantic in the years 2008 - 2012 (off Iceland, Norway, the Faroe Islands and Scotland). This extensive and extensive sample collection will then be used in further research projects. The results of a genetic analysis with 24 genetic markers showed that local herring stocks in fjords in Norway were significantly different from all other stock units. However, no significant differences were found for the possible stem units. Other more sensitive methods, such as DNA monopoly analysis (SNPs), may be able to differentiate between the strains, but this research has already begun in a new follow-up project. The biological information collected in the project did not differentiate between possible stem units. Studies of the Icelandic summer spawning herring and the Norwegian-Icelandic spring spawning herring showed differences in body color, water and fat content as well as stage of puberty and weight. No results have been obtained from the mill analyzes, but they will be published in connection with a doctoral project at the University of Iceland.

The aim of the project was:

· To develop a genetic approach based on 20-25 microsatellite loci to study the genetic variation of herring stocks in the Northeast Atlantic Ocean

· To use genetic, biological and otolith characters as discriminating parameters for stock identification

· To analyze physicochemical characteristics of different herring stocks

Sustainable fisheries management and quota decisions made by authorities are based on knowledge on fish stock structures and their sizes. Herring is a highly migratory fish species, and therefore it is likely to show low genetic differences among stocks. The mixed stock herring fishery creates considerable problems for the industry and the management of the stocks. In this project more than 4,500 individuals were sampled from 9 putative herring stocks in the Northeast Atlantic Ocean during the years 2008 and 2012. The sampling accomplished in the project is extensive and valuable for future research projects. The results of the genetic study based on 24 microsatellite genetic loci showed that the local Norwegian fjord stocks were significantly different from all other putative stocks. The other Northeast Atlantic herring stock units were not found to be significantly different. Power analyzes performed during this study revealed that sampling scheme, protocols and genetic design were sufficient to detect any level of genetic differentiation around 0.001. Therefore, a more sensitive type of genetic markers are needed for the problem addressed, such as SNPs (single nucleotide polymorphism) and that work has already started. Biological parameters alone did not have enough discriminating power for stock identification. The Icelandic summer ‐ spawning herring (ISSH) and the Norwegian spring ‐ spawning herring (NSSH) differed mainly in color and water / fat content. The herring from the two stocks were also found to be different in relation to maturity and weight. The methodology of otolith microstructure analyzes and their results will be published later in a PhD thesis at University of Iceland.

Report closed until 01.02.2015

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Reports

Processing qualities of different potato strains

Published:

01/03/2012

Authors:

Valur Norðri Gunnlaugsson, Jónatan Hermannsson, Þórdís Anna Kristjánsdóttir, Aðalheiður Ólafsdóttir, Irek Klonowski

Supported by:

Adaptation Fund of the Horticultural Farmers' Association

Contact

Valur Norðri Gunnlaugsson

Research Group Leader

valur.n.gunnlaugsson@matis.is

Processing qualities of different potato strains

4 varieties were bred, Annabelle, Milva, Salome and Gullauga. The cultivation took place on Korpa in typical peatlands and Annabelle and Gullauga had a better harvest than the other varieties, in addition to which Gullauga had the highest dry matter content. The varieties came out very differently from the production episode that was carried out at Sölufélagið. Salóme's utilization was by far the best, Gullauga had deep eyes that reduced the utilization, part of Milva was damaged and was sorted out and Önnubelle's shape prevented good utilization. In the consumer survey, participants identified smaller differences between potato varieties than they did in the last survey, and the participants' tastes were different. In general, the Gullauga potatoes came out best in the consumer survey, although the differences between varieties were only significant in appearance. All varieties still appear to be processable after storage at 5.7 ° C for up to 200 days after recording, although some varieties have begun to germinate, albeit to varying degrees. In terms of processing, Milva, Salome and Gullauga all came out well in terms of utilization, but the judging group was most impressed by Gullaugar's taste quality.

Four different strains of potato were tested in processing of precooked potatoes. The strain Salome had best yield, but the strain Gullauga was best liked by consumers, which is in contrast with previous results. All four strains still qualified for processing after storage for almost 200 days at 5.7 ° C, although some strains had started sprouting. The strains Milva, Salome and Gullauga all had good yield, however, group of sensory panelist liked the flavor of Gullauga. 

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Reports

Processing properties of different potato varieties

Published:

01/02/2011

Authors:

Valur Norðri Gunnlaugsson, Jónatan Hermannsson, Þórdís Anna Kristjánsdóttir, Aðalheiður Ólafsdóttir, Vilberg Tryggvason

Supported by:

Adaptation Fund of the Horticultural Farmers' Association

Contact

Valur Norðri Gunnlaugsson

Research Group Leader

valur.n.gunnlaugsson@matis.is

Processing properties of different potato varieties

4 varieties were grown. Seeds of Belana and Annabelle came from producers abroad, seeds of Premier and Gullauga were obtained from Bergvin at Áshóll. The cultivation took place at Korpa and was primarily a production of raw materials for processing tests, but crop measurements were made. The variants came out very differently from the processing component. The new varieties Annabelle and Belana seem to be quite suitable for processing pre-cooked potatoes, although the "kidney-shaped" shape of Annabelle caused some disappointment, but this shape has not been a problem in previous experiments with this variety. In the consumer survey, participants identified a large difference between potato varieties and the participants' tastes were different. In general, the Annabelle potatoes came out best in the consumer survey.

Four different strains of potato were tested in processing of precooked potatoes. The strain Annabelle was best liked by consumers, but the kidney like shape did cause problems during processing.

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Reports

Let's look at the yellow from fishing in the stomach - a study of factors that affect the value of cod / Factors influencing the quality and value of the Icelandic cod; a value chain perspective

Published:

01/09/2010

Authors:

Helga Gunnlaugsdóttir, Jónas R. Viðarsson, Ásta M. Ásmundsdóttir, Cecilia Garate, Hrönn Jörundsdóttir, Ingibjörg G. Jónsdóttir, Sigurjón Arason, Vordís Baldursdóttir, Þorsteinn Sigurðsson, Sveinn Margeirsson

Supported by:

Increased value of seafood (AVS), HB ‐ Grandi, Guðmundur Runólfsson hf, Fiskistofa, Hafrannsóknastofnunin, Matís

Let's look at the yellow from fishing in the stomach - a study of factors that affect the value of cod / Factors influencing the quality and value of the Icelandic cod; a value chain perspective

The aim of this project was to gather more detailed information than has previously been done on the chemical composition, processing properties and value of cod in the value chain. The main results of the study are:

• There was not much difference in the carcass of cod by season, but the carcass coefficient was slightly higher in December than around the spawning season (February-May) when it was lowest. No association was found between fish body and liver fat content.

• There was a positive relationship between hepatic index and liver fat content (R2 = 0.55). However, the relationship was not linear, but the fat content increased rapidly at a low liver factor but less as the liver factor increased. Likewise, the fat content of the liver increased with length and age in both hens and females.

Liver fat content, fish weight or body mass index do not provide conclusive evidence of fillet utilization. Likewise, the water content and water resistance of the fillets had little or no effect on production efficiency or emissions.

• The summary result of the assessment of the effect of sex, sexual maturity and age on fillet utilization is that there is a difference in fillet utilization between individual fishing trips, this difference seems to be somewhat dependent on the maturity of the fish and is according to available data lowest at maturity stage 4 (ie fish in spawning or spawning). It should be noted, however, that there is a considerable imbalance in the database regarding the distribution of puberty in individual fishing trips and there are relatively few samples of fish from stages 3 and 4 compared to stages 1 and 2.

A comparison was made of the concentration of PCB7 in cod directly from the sea on the one hand and after processing, ie in frozen fillets, on the other. There was no significant difference in the concentration of PCB7 in whole fish and frozen cod fillets, so fish processing does not seem to affect the concentration of these substances in the fillets.

• There was no statistically significant relationship between iron concentration (Fe), selenium (Se), lead (Pb) or PCB7 and gender, age or puberty. There is a statistically significant relationship between the concentration of mercury in the flesh of cod (ie in fillets) and age, length and sexual maturity. Mercury is known to accumulate in the flesh of fish with age and the results of this study are consistent with and based on these results.

The aim of this project is to collect more detailed data about the factors influencing the quality and value of the Icelandic cod during processing, were the end product is frozen fillet. Data were collected from 2007 to 2008 on fillet yield, water content, water capacity, gaping, parasites as well as the chemical composition (nutrients & undesirable substances). These variables are important for the quality and profitability of the cod industry. Emphasis has been laid on connecting these variables to data about fishing ground, season of fishing, sex, sexual maturity in order to increase our understanding on how it is possible to maximize the value of the catch. In addition, the liver from each individual cod was collected and the fat and water content analyzed. The results from this study show that there is a nonlinear relationship (R2 = 0,55) between the liver condition index and the fat content of the liver.

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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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Reports

Blue whiting as a target food

Published:

01/03/2008

Authors:

Margrét Geirsdóttir, Ragnar Jóhannsson

Supported by:

Rannís

Contact

Margrét Geirsdóttir

Project Manager

mg@matis.is

Blue whiting as a target food

The aim of the project was to answer the research question: What bioactivity can be obtained from peptides extracted from blue whiting with enzymes? Bioactivity is a prerequisite for the use of blue whiting as a target food. Isolated blue whiting proteins were used as raw materials. The study showed that degraded blue whiting proteins have bioactivity. However, the sensory properties of products did not prove to be good enough and yields were low. This was especially so due to the difficulty of obtaining fresh blue whiting as a raw material. In the second steps of the project, it was decided to use cod. The aim was to investigate in particular whether isolated cod proteins had other properties than hacking in terms of sensory evaluation and antihypertensive properties of products. The result was that no differences in these characteristics were found in the study. The project investigated the interaction of hydrolysis with enzymes and processing properties and bioactivity. The interaction of hydrolyzed blue whiting proteins isolated by a new method and their bioactivity has not been performed before and was an international novelty. The project acquired extensive knowledge in the field of enzyme degradation and the bioactivity properties of protein products.

The aim of the project was to answer the question: What kind of bioactive properties do peptides produced by enzyme hydrolysis of blue whiting have? Some sort of bioactivity is needed if they are to be used in functional food. The substrate for the hydrolysis was isolated blue whiting proteins. Well-known, commercially available enzymes were used to hydrolyze the proteins to different degrees of hydrolysis (%DH). The blue whiting hydrolysates showed bioactive properties, but their sensory characteristics were not good. Furthermore, the yield of the process was low. The reason for this was a shortage of fresh raw material. Thus, in the next steps cod was therefore used. The main aim was to study whether different sensory and bioactive characters were achieved when isolated proteins were used compared to mince. The results of the project indicate that there is no difference. In the project the connection between enzyme hydrolysis and functional and bioactive properties was examined. Main emphasis was on the effect of using isolated proteins as raw material for enzyme hydrolysis. In the project important knowledge in the field of enzyme hydrolysis and bioactivity was gained that will facilitate future research.

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