Contact
Kolbrún Sveinsdóttir
Project Manager
kolbrun.sveinsdottir@matis.is
This report is closed.
Tag: Freezing
Contact
Sigurjón Arason
Chief Engineer
sigurjon.arason@matis.is
Effect of salt content in slurry ice on quality of fresh and thawed Atlantic mackerel (Scomber scombrus)
The aim of the experiment was to improve methods of cooling and storage of fresh produce in order to improve the quality of frozen mackerel products. A comparison was made of cooling in conventional ice scrapers and salt-improved ice scrapers. By adding salt to the ice scraper, it was hoped that the temperature of fresh mackerel could be lowered and thus its quality maintained longer. The fresh mackerel was stored for up to seven days after fishing. Another aim of the study was to investigate whether this different cooling of fresh mackerel affects the deterioration of the quality of frozen mackerel products. The results showed that the temperature distribution in the pots was related to salt concentration as lower temperatures were obtained in pots with higher salt content (3.3%). On the other hand, the cold storage had a much greater effect on the quality factors such as the freshness and release of the mackerel products compared to the effect of pre-cooling, as the effect of different salt concentrations in the ice scraper was negligible in terms of these quality factors.
The present experiment is part of the research project - Increased value of mackerel through systematic chilling. The aim of this study was to improve methods of chilling and storing of fresh products in order to obtain better quality of frozen mackerel products. This project was carried out to develop slurry ice mixture with addition of extra salt, with the intention of temperature decrease during chill storage up to seven days after catch. Secondary objective of this research was to investigate if different chilling condition of fresh fish has an effect on the quality assignment of long-term frozen mackerel products. The results showed that temperature distribution in the tubs was correlated to the salt concentration where lower temperature was obtained in the tub with higher salt content (3.3%). Furthermore, freshness, gaping and peritoneum deterioration have been affected by the storage process but not by different salt concentration in slurry ice during chilled storage. Due to high quality variation within the same group of the mackerel is needed to conduct more methods for quality evaluation such as oxidation analysis and sensory analysis.
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Sigurjón Arason
Chief Engineer
sigurjon.arason@matis.is
Effects of bleeding methods on the quality and storage life of cod and saithe products
The aim of the project was to examine the effect of different bleeding methods on the quality and shelf life of different cod and saithe products. By identifying ideal conditions for bleeding, gutting and bleeding, it is possible to prevent product defects due to blood and at the same time increase the stability of the products in transport and storage. The fish were either bloodied in the hands and in the machine. Bleeding took place in slush or sea and the effects of different bleeding times were examined. The effect of waiting time on tires before bleeding was also assessed, as well as bleeding and gutting the fish in one step or two steps (gutting performed after bleeding). The products studied in this project were chilled and frozen cod and saithe products, as well as salted cod products. Of the variables studied in this project, their importance differed in terms of which fish species were involved and what the final product was. When comparing comparable sample groups of cod and saithe, it is seen that different conditions are suitable for each species. This supports the theory that it is probably not possible to transfer the best bleeding method of cod to saithe and vice versa. Bleeding time and type of bleeding agent (sludge vs. seawater) had a decisive effect on the stability of the cod and saithe products examined. Cod products, both chilled and frozen, from raw material soaked in sludge generally resulted in improved quality and stability compared to if soaked in seawater. In contrast to cod, the bleeding of saithe into the sea generally resulted in a stable end product. The way the fish were bled and gutted also had a decisive effect on the final products. In the case of frozen cod products, raw and gutted raw material in one step generally yielded a more stable product compared to raw material that was gutted after bleeding had occurred (two steps). Salted products, on the other hand, were much more stable in storage if the raw material was gutted after bleeding. Different results were also obtained for saithe depending on the final product involved. Bleeding and gutting of saithe in a machine had a positive effect on the shelf life of chilled products compared to if made by hand. Machine bleeding and gutting, on the other hand, resulted in a much more unstable product in the cold. The results of the project show that the effects of different bleeding methods are quite dependent on the raw material as well as the final product involved.
The main objective of the project was to study the effects of different bleeding methods on quality and storage life of various cod and saithe products. Products defects due to blood residues can be prevented by optimizing bleeding protocols, and hence increase the quality and storage life of the products. For this, fishes were either bled and gutted by hand or by machine. The bleeding (blood draining) was carried out with seawater or slurry ice, and the effects of different bleeding times in the tanks were also investigated. Moreover, the effects of waiting time (on deck) before bleeding, as well as the procedure of bleeding technique (bleeding and gutting in one procedure vs. gutting after blood draining) were investigated. The various products evaluated were chilled and frozen cod and saithe products, and salted cod products. The importance of the different parameters investigated in this project varied considerably with regard to fish species and the final products. Comparison of parallel treatments groups of cod and saithe demonstrated that optimum bleeding procedures are different for each species. Waiting time on deck and bleeding media (slurry ice vs. seawater) significantly affected the storage life of the cod and saithe products. Cod products, both chilled and frozen, from fish bled in slurry ice generally resulted in improved quality and storage life compared to fish bled in seawater. In contrast to cod, bleeding or saithe in seawater resulted however in more stable products. The procedure during bleeding and gutting also had great impact on the storage life of the various products studied. Shorter storage life of salted cod products was generally observed when the raw material was bled and gutted in one step compared to when gutting was performed after bleeding (two steps). Rather conflicting results were, however, observed for saithe and were depending on the type of final product. Bleeding and gutting of saithe by machine improved the storage life of chilled products compared to when the saithe was bled and gutted by hand. The machine procedure had, however, negative effects on the storage life of the frozen saithe products. Overall, the results of this project indicate that the effects of different bleeding methods are highly relative to fish species as well as the final product of interest.
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Kolbrún Sveinsdóttir
Project Manager
kolbrun.sveinsdottir@matis.is
Experiments with the processing of sea urchin eggs
In this project, three experiments were performed with different goals. The aim of the first experiment was to examine the quality of sea urchin eggs and to test the rapid freezing of eggs with exports in mind. In the second experiment, branched dextrin sugars (Glico) and alginate were used to strengthen the outer layer of the eggs, the purpose was to find a substance that could replace alum to keep the eggs better from processing to the buyer. In the third experiment, the aim was to investigate whether it was possible to process sea urchin roe by heat treatment as a bulk product and also whether it was possible to separate the processing in time, ie. whether the pots could be opened and the roe packed in larger units so that they could be handled elsewhere than where the pots were opened.
In this project three experiments were undertaken. The goal in the first one was to explore the quality of gonads (sea urchin roes) and try to instant-freeze it for export. In the second experiment clusterdextrin and alginate was used to make the surface of the roes stronger. The purpose of that experiment was to find a substitute for alum for the gonads to keep their shape during the time from processing to buyer. In the third experiment the goal was to explore if it was possible to process gonads with heating in a large quantity and if it was possible to separate the stages of processing so tha the gonads could be collected and packed in one location, then further processed in another.
Report closed until 01.07.2016
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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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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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Sigurjón Arason
Chief Engineer
sigurjon.arason@matis.is
Freezing and thawing of Greenland halibut - experiments and CFD simulation
Freezing and thawing of halibut were studied experimentally and computerized thermodynamics (CFD) models. Whole pallets of semi-frozen halibut were placed in a cold store and the air temperature and halibut temperature in different places on the pallet were measured by thermometers. The time taken for the halibut to freeze from -10 to -5 ° C below -15 ° C ranged from one to four days depending on the location of the pallets. In thawing experiments, both individual bags and twenty bags, stacked on pallets, were examined in the temperature-controlled cold rooms of Matís and UI. The heating of a frozen product was mapped under conditions that may occur during unloading from freezer trawlers or 10 - 20 ° C air temperature. The results of the experiments were compared with the results of three-dimensional heat transfer models, and there was generally good agreement between them. At 10 p.m. storage at 12.6 ° C air temperature raised the temperature in individual bags from about -26 ° C to approx. ‐5 ° C. At such a long temperature load, the temperature in pallet bags rose from -22.5 ° C to from -17 to -3 ° C, which shows how homogeneous the heat distribution can be with prolonged heat load. The results of the CFD model showed that 10 m / s wind during loading significantly accelerates the thawing of frozen fish on pallets.
Freezing and thawing of Greenland halibut was investigated with experiments and computational fluid dynamics (CFD) models. A whole pallet of half ‐ frozen halibut was put in a frozen storage and ambient temperature and fish temperature at different locations in the stack monitored. The required freezing time from ‐10 - ‐5 ° C down to ‐15 ° C was one to four days depending on the location within the stack. In the thawing experiments, both single, free standing halibut bags and twenty halibut bags stacked on a pallet, were investigated in an air climate chamber. The warm up of full ‐ frozen product was mapped under typical temperature conditions during unloading of products from freezer trawlers, ie at 10 - 20 ° C ambient temperature. A good comparison between the CFD simulation and experimental results was obtained. Fish temperature increased from ‐26 ° C to - 5 ° C inside single bags when thermally loaded for 10 hours at 12.6 ° C ambient temperature. Equally long temperature abuse for the whole pallet, initially at ‐22.5 ° C, resulted in a very inhomogeneous temperature distribution from ‐17 to ‐3 ° C. The results from the CFD modeling showed that 10 m / s wind during unloading seriously accelerates thawing of frozen fish.
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Valur Norðri Gunnlaugsson
Research 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.