Reports

Effect of post ‐ slaughter time intervals on yield and quality of farmed cod

Published:

01/11/2011

Authors:

Kristín Anna Þórarinsdóttir, Aðalheiður Ólafsdóttir, Kolbrún Sveinsdóttir, Ásbjörn Jónsson, Hannes Magnússon, Kristján G. Jóakimsson, Sveinn K. Guðjónsson

Supported by:

AVS (R 11 006‐010)

contact

Aðalheiður Ólafsdóttir

Sensory evaluation manager

adalheiduro@matis.is

Effect of post ‐ slaughter time intervals on yield and quality of farmed cod

The purpose of the experiment was to investigate whether the waiting time (0, 2, 4 hours) from slaughter to processing had an effect on weight uptake during injection and the properties of frozen fillets. In addition, changes in thawed fillets during refrigerated storage were assessed. Changes in weight, chemical content, water resistance, microbial growth and levels of degradable substances were monitored, as well as the fillets were sensitized. For comparison, untreated fillets were used. Weight gain was greater as the waiting time became longer. Salting increased the water resistance of the fillets and reduced shrinkage during thawing and boiling compared to untreated fillets. The injected fillets were therefore also juicier. Higher water resistance of injected fillets is explained by the fact that a higher proportion of water was inside the muscle cells in the injected fillets, while the extracellular fluid was higher in untreated fillets and proportionally more water was loosely bound. The number of micro-organisms was higher in injected fillets, as expected, as the injection spreads micro-organisms throughout the muscle instead of being found only on the surface of the muscle after filleting. Damage symptoms therefore became more pronounced in injected fillets as the storage of thawed fillets progressed over a 2-week period, despite the fact that the fillets were not initially considered more relaxed. Desalination of salted fillets was higher according to TBA values, but its effect was not noticeable on sensory evaluation. Higher salt content was thought to increase the death stiffness of the injected fillets and give a rubberier and stiffer texture compared to untreated fillets. The appearance of injected fillets was poorer, they were a bit darker and more uneven than untreated fillets.

The aim of the experiment was to evaluate the effect of post ‐ slaughter time intervals on injection yield and characteristics of frozen cod fillets. In addition, to evaluate changes in thawed fillets during chilled storage. Weight gain by injection was higher as the waiting time was longer. Salting increased water retention during storage and cooking in comparison to untreated fillets. Therefore, the injected fillets were also juicier. The higher water retention of injected fillets was explained by a higher percentage of water within the muscle cells while the ration of intercellular fluid was higher in untreated fillets. Spoilage became more pronounced in injected fillets over 2 weeks of chilled storage of the fillets after thawing. Oxidation was higher in salted complex as expressed by higher TBARS ‐ values, but the effect was not observed in sensory analysis. Higher salt content seemed to increase rigor contraction in injected fillets and result in a more rubbery texture of the injected fillets, which were also slightly darker and more heterogeneous than untreated fillets.

Report closed until 01.01.2015

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Reports

Effects of additives and different salting methods on the utilization and quality of farmed cod products / Effects of additives and different salting methods on yield and quality of farmed cod products

Published:

01/11/2011

Authors:

Kristín Anna Þórarinsdóttir, Aðalheiður Ólafsdóttir, Kolbrún Sveinsdóttir, Ásbjörn Jónsson, Hannes Magnússon, Kristján G. Jóakimsson, Sveinn K. Guðjónsson

Supported by:

AVS (R 11 006‐010)

contact

Aðalheiður Ólafsdóttir

Sensory evaluation manager

adalheiduro@matis.is

Effects of additives and different salting methods on the utilization and quality of farmed cod products / Effects of additives and different salting methods on yield and quality of farmed cod products

The aim of the experiments was to examine the effect of salting methods and brine composition on the utilization and quality of products processed from farmed cod before freezing to death. Fillets were either injected or injected and pickled. The brine was of different salinity, in addition to which the use of polyphosphate and a mixture of citrate and ascorbate was examined. Changes in utilization, water content, water resistance and quality were monitored over a 9-month period in frost. The results of the project show that it is possible to increase salt uptake and weight changes of fillets by changing processing processes even though the fish has not died of freezing. There was a definite difference in efficacy symptoms in the first 3 months depending on whether the fillets were only injected or injected and pickled. With longer storage, the difference between the groups decreased. At the beginning of storage, factors that characterize fresh products were prominent, but as the storage period progressed, factors such as cold storage odor, freezing taste, craving and tableware odor became more prominent. The use of phosphate and a mixture of citrate and ascorbate appeared to be able to reduce the development to some extent according to the results for TBARS, but the effect was not found in color measurements or sensory evaluation. 

The aim of experiments was to investigate the effects of different salting methods and brine composition on yield and quality of products, processed from pre ‐ rigor farmed cod. Fillets were either injected or injected and brined. Different brine concentrations were used, as well as polyphosphates and a mixture of citrate and ascorbate. Changes in yield, water content, water retention and quality of the products were followed over 9 months period of frozen storage. Results show that it is possible to increase the salt uptake and weight changes of the fillets by altering processing procedures for the pre ‐ rigor fish. The curing characteristics of the products depended on salting methods, ie if the fillets were only injected or injected and brine salted before freezing, especially during the first 3 months. Longer storage time reduced the difference between the groups. At the beginning of the storage, freshness characteristics were strong but during storage attributes like frozen odor and taste, rancid taste and dish cloth odor become predominant. Oxidation was reduced by use of phosphate and the mixture of citrate and ascorbate, as indicated by lower TBARS ‐ values. However, the effect was neither detected in results from color measurements nor sensory analysis.

Report closed until 01.01.2015

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Reports

Processing and quality control of farmed cod

Published:

01/04/2009

Authors:

Kristín Anna Þórarinsdóttir, Valur Norðri Gunnlaugsson, Guðrún Anna Finnbogadóttir, Kristján Jóakimsson, 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

Processing and quality control of farmed cod

The report is a summary of the results of the project "" Processing and quality control of farmed cod "which was carried out in collaboration between HG and Matís. Ways were sought to develop traditional methods for the production of fresh, frozen and lightly salted products so that they could be used for farmed fish. The aim of the project was to provide products from farmed cod with valuable and varied products that met the quality requirements of the market. Processing of farmed cod must be carried out before death. Otherwise there is a risk that the formation will be so great that the products will in the worst case be unsaleable. Chilled and loose-frozen products are of comparable quality to products made from wild cod. However, the properties are not the same and this is reflected in the taste and texture properties, among other things. Wild cod is coarser and often juicier, but farmed cod has a more meaty and stuttering texture and is sweeter in taste. Processing for death solidification means that traditional salting processes for farmed fish cannot be used. In light salting, methods such as injection and prolongation of the pickling time can be used to reduce the negative effects of lethal stiffness on uptake during normal course of action. Salting and temperature conditions need to be very well controlled to minimize the risk of microbial growth as very low salinity is used in the production of lightly salted (2% salt) products.

This report summarizes the results from the project "Processing and quality control of farmed cod" where processing and salting methods for farmed cod were developed in co-operation of HG (HradfrystihusidGunnvor Ltd) and Matís ohf. The main difference in processing of farmed and wild cod is that farmed cod has to be processed before rigor mortis. Otherwise there is a high risk of gaping and quality defects in products that are not accepted by markets. Chilled and IQF products processed from pre-rigor farmed cod were of similar quality as products from wild cod. However, farmed cod products have different properties, they have a sweeter taste and more "meaty" and firmer texture than products from wild cod which are softer and juicier. Processing of farmed cod before rigor retards weight increase and salt uptake during light salting. The effects of rigor can be reduced using brine injection and increasing brining time from traditional processed for farmed cod. Salting conditions and temperature must be carefully controlled during the process to avoid microbial growth at the low salt levels used in production of light salted (2% NaCl) products.

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Reports

Comparison of microstructure between farmed and wild cod

Published:

01/12/2008

Authors:

Valur Norðri Gunnlaugsson, Guðrún Anna Finnbogadóttir

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 microstructure between farmed and wild cod

The aim of this project was to build up knowledge through image analysis to facilitate the processing and product development of farmed cod. In the project "Future cod", imaging revealed remarkable results where a large difference was found in the structure of the flesh in wild cod and farmed cod. The purpose of this project was to examine this difference in more detail and try to find reasons for it. The results of the project confirmed this large difference in intercellular space, as had been seen before, but it was only seen in samples taken from live fish. There was little difference in pre-rigor samples taken, whether farmed or wild. After post-rigor, only wild fish were sampled, as the processing properties of farmed cod were weak after freezing. It was found that the extracellular space increased again in wild fish during death. Numerous other measurements were made on these samples in step 4 of this project and a close connection could be seen with the results for the proportion of intercellular cells in these samples. The mobility of water molecules was lower in wild cod muscles, which was consistent with the greater intercellular space than in farmed fish. On the other hand, the water content of the wild cod was higher. The results indicated that the structure and properties of the muscle were quite different in these groups. The research was part of the project "Processing and quality control of farmed cod, more specifically a summary for work component 3.

In previous project there was much difference in gap between cells samples from wild and farmed cod. In this project phase the aim was to confirm this difference and try to identify the reason for it. The results showed a difference in microstructure between wild cod and farmed one, when samples were taken from live fish. This difference was not a distinct, when samples from pre-rigor and post rigor fish where analyzed. In project phase 4 these samples where used for number of measurement. The results from the microstructure analysis were in harmony with results from measurement of water content and water mobility.

Report closed until December 2011 / Report closed until December 2011

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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

Comparison of farmed and wild cod fillets during light salting

Published:

01/12/2008

Authors:

Valur Norðri Gunnlaugsson, Guðrún Anna Finnbogadóttir, María Guðjónsdóttir, Kolbrún Sveinsdóttir, Kristján Jóakimsson, Sigurjón Arason

Supported by:

AVS Fisheries Research Fund, Rannís Technology Development Fund

contact

Valur Norðri Gunnlaugsson

Group Leader

valur.n.gunnlaugsson@matis.is

Comparison of farmed and wild cod fillets during light salting

The aim was to go through the processing process of lightly salted products made from wild cod after freezing and farmed cod before freezing, from filleting to consumers. This basic information was to be used to formulate new processing and transport processes for the export of lightly salted farmed fish products to southern Europe. There was a significant difference between the characteristics of pre-rigor cod farming and wild post-rigor cod during spraying and pickling. The uptake of brine was much higher in wild cod, but the farmed fish picked up a small amount of brine, which resulted in a small weight gain and low salt content. This large difference in salt uptake affected most of the variables examined, such as the water content and sensory properties of fillets. The difference was mainly in the texture factors, as the wild cod generally had a softer, juicier and softer texture, as it was more watery. The shelf life of farmed fish was longer. The main conclusion was that farmed fish products have different properties than wild fish products, but not worse. However, the timing of processing makes light salting difficult. If pre-rigor fish is salted immediately after filleting, death stiffness counteracts salt absorption. Therefore, traditional processes in the processing of wild post-rigor fish can not be transferred to prerigor volcanic fish. The research was part of the project "Processing and quality control of farmed cod, more specifically a summary for work component 5.

The aim of this part of this project was to look at the process of lightly salted cod, both from wild catch and farmed cod. To gather information from the processing part and try to improve the process and adjust the process to farmed cod. The results from this phase of the project strongly indicate that there is a big difference between farmed and wild cod when we look at physical properties. After injection and brine salting of the cod the wild cod had gained much weight while the farmed one did not gain any weight and therefore had low salt content. This difference in brine uptake resulted in difference between the sample groups in almost every research segment of this phase. The wild cod had more salt content and therefore more water content which resulted in more tender, softer and juicer fillets. It is obvious that those products are of different nature and farmed cod might not be suitable for the salting process because of limited brine uptake. However, despite the low salt content of the farmed cod, the fillets had better shelf life than the wild cod. The farmed cod has other characteristics than wild catch, and those characteristics have to be utilized in processing and production of consumer goods.

Report closed until December 2011 / Report closed until December 2011

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Reports

Fat tolerance of cod

Published:

01/07/2008

Authors:

Jón Árnason, Rannveig Björnsdóttir, Helgi Thorarensen, Ingólfur Arnarson

Fat tolerance of cod

The purpose of this study was to investigate the effect of fat content in feed on the growth and cleaning of cod of different sizes. Knowledge of the nutritional needs of fish is a necessary prerequisite for the preparation of feed for them. Two-size cod (120 g and 600 g) were fed (in triplicate) for 12 weeks on feed containing 10.0%, 13.5%, 21.2%, 24.5% and 27.7% fats in dry matter. Different fat content did not affect growth (SGR), body mass index (CF), fillet utilization, liver fat content or fillet fat content. In the smaller fish, the feed index (FCR) decreased with increased fat in the feed. The feed fat did not affect the fat content of offal without liver in the smaller fish (120g) but in 600 g fish the fat in the intestines increased with increased fat content of the feed. The fat content did not affect the proportion of gutted weight of the total weight in the 600 g fish, but in the smaller fish the proportion decreased with increased fat in the feed. Liver ratio (HSI) in 600g fish was not dependent on the fat content of the feed, but there was a positive correlation between feed fat and HSI in the 120 g fish. This means that the fat tolerance of cod in terms of liver ratio depends on the size of the fish.

Detailed knowledge of the nutritional requirements of fish is essential for feed formulation. The aim of this research was to investigate the effects of different lipid content in diets for Atlantic cod of different size. Cod of two size groups (initial weight 120 grams and 600 grams) were fed, in triplicate, for 12 weeks diets containing 10.0%, 13.5%, 21.2%, 24.5% and 27.7% lipid in dry matter. Different lipid content in the diet did not affect growth (SGR), condition factor (CF), fillet yield, lipid content in liver or lipid content in fillet. In the smaller fish, FCR was reduced with increased diet lipid. The lipid content in the diet did not affect the lipid content of intestines in the 120 grams fish but in the 600 grams fish there was a positive correlation between lipid content in diet and intestines. Dietary lipid did not affect gutted weight (calculated as the percentage of round weight) in the 600 grams fish but in the 120 grams fish, the percent gutted weight decreased with lipid content of the diet. The Heposomatic index (HSI) in the 600 gram fish was not affected by the lipid content of the diet but dietary lipid content significantly affected the HSI in the smaller fish. This indicates that the lipid tolerance of Atlantic cod, with respect to the effect on HSI, is size dependent.

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