Tag: Shelf life

Reports

Development of Quality Index Method and shelf life of thawed mackerel (Scomber scombrus) / Development of Quality Index Method and storage life of thawed mackerel (Scomber scombrus)

Published:

01/07/2010

Authors:

Kolbrún Sveinsdóttir, Patricia Miranda Alfama, Aðalheiður Ólafsdóttir, Emilía Martinsdóttir

Supported by:

AVS Fisheries Research Fund, UNU School of Fisheries, United Nations University

Contact

Kolbrún Sveinsdóttir

Project Manager

kolbrun.sveinsdottir@matis.is

Development of Quality Index Method and shelf life of thawed mackerel (Scomber scombrus) / Development of Quality Index Method and storage life of thawed mackerel (Scomber scombrus)

The QIM method (Quality Index Method) is an objective, fast and reliable sensory evaluation method that has been developed to assess the freshness of fish. The aim of the study was to prepare a QIM rating scale for thawed mackerel (Scomber scombrus) stored in ice at 0 ° C and to test its use in a shelf life test. The mackerel was evaluated by sensory evaluation according to QIM and DA method (generic descriptive analysis), microorganisms (TVC and H2S producing) were also counted and histamine was measured for up to 9 days after thawing. The result of the study was the QIM method for thawed mackerel which was developed and tested in a shelf life test. Quality factor - QI (total grade) increased linearly with ice shelf life. The QIM method for thawed mackerel is based on an assessment of quality factors such as the appearance of redness, texture, color and shape of the eyes, the color and odor of the gills, the appearance of mucus in the gill and gill leaf and the intestinal dissolution, and the total fish can reach a maximum of 19. The project also developed a method (general descriptive analysis-DA) for evaluating boiled mackerel. The main characteristics of the mackerel immediately after thawing were the smell and taste of fresh oil, the smell of metal and the sweet smell / taste that faded with the storage period. What limited the shelf life were sensory properties that describe the symptoms of damage, such as the stench and taste that can be noticeable in fatty fish after prolonged cold storage. According to a sensory assessment of boiled mackerel fillets, the shelf life of thawed mackerel after five months of cold storage is about 4-6 days. The total number of micro-organisms and H2S-producing micro-organisms was lower than is usually seen at the end of the shelf-life of micro-organisms. Histamine was not detected (<5 ppm) in thawed mackerel during the 9-day ice-storage period.

The Quality Index Method (QIM) is an objective, rapid and reliable sensory method. The aim of the present study was to develop a QIM scheme for frozenthawed Atlantic mackerel (Scomber scombrus) stored in ice at 0 ° C and evaluate the scheme in a shelf life study. The mackerel was evaluated with sensory evaluation (QIM and generic descriptive analysis (DA)), microbial counts (Total viable counts (TVC) and H2S-producing bacteria) were estimated and histamine measured for up to nine days. The main result of this study vas the QIM scheme to evaluate freshness of frozen-thawed Atlantic mackerel storage in ice which was developed and tested in a shelf life study. The quality index - QI (sum of scores) increased linearly with storage time on ice. The QIM for thawed mackerel is based on the evaluation of quality parameters dealing with the appearance on back and belly side, texture, color and shape of eyes, mucus, color and odor of gills and appearance of gill filaments and dissolution of viscera. The maximum sum of scores (QI) can be 19. A method to evaluate cooked mackerel was also developed (general descriptive analysis-DA). Newly thawed mackerel had fresh oil, metallic and sweet odors and flavors. The main limitation of shelf life in chilled storage after thawing were sensory characteristics describing spoilage such as rancid odor and flavor which can be prominent in fatty fish species after extended frozen storage. According to sensory evaluation of cooked mackerel, the shelf life of thawed mackerel after five months of frozen storage is around 4-6 days. Counts of TVC and H2S producing bacteria were relatively low at the end of shelf life. Histamine was not detected (<5 ppm) in the thawed mackerel during the storage time of nine days on ice.

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Reports

Shelf life of vacuum ‐ packed smoked herring fillets

Published:

01/06/2010

Authors:

Franklín Georgsson, Margeir Gissurarson

Supported by:

AVS Fisheries Research Fund

Shelf life of vacuum ‐ packed smoked herring fillets

The aim of the study was to examine the shelf life of smoked herring fillets in vacuum-packed packaging and to examine its effect on the shelf life of the product if preservatives are not used and if sorbate is used instead of benzoate, which is used in conventional production. This study showed that the use of preservatives has a significant effect on the shelf life of smoked herring fillets. It was also stated that the sorbate treatment of herring fillets provided the best preservation against microbial growth and also the sorbate treatment of herring fillets proved to be the best in informal sensory evaluation. Whether this is due to the sorbate's inhibition of microbial growth or whether it reduces the rate of chemical and physical degradation factors compared to herring fillets with benzoate or without preservatives needs further research.

The object of this project was to evaluate the shelf life of vacuum packed smoked herring fillets and to evaluate whether the use of the preservatives benzoate or sorbate had any effect on the shelf life of the product Results showed that treatment of the smoked herring fillets with preservatives greatly affected the shelf life and that sorbate treatment of the herring fillets provided the best defense for bacteria growth and also gave best results in an informal sensory testing during the shelf life study. Whether this is due to inhibitory role of sorbate on bacteria growth or that sorbate slows down chemical and physical degradation in comparison to herring fillets with benzoate or without any preservatives needs further investigation.  

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Reports

The effect of cooling methods at processing and use of gel-packs on storage life of cod (Gadus morhua) loins - Effect of transport via air and sea on temperature control and retail-packaging on cod deterioration

Published:

01/05/2010

Authors:

Emilia Martinsdóttir, Hélène L. Lauzon, Björn Margeirsson, Kolbrún Sveinsdóttir, Lárus Þorvaldsson, Hannes Magnússon, Eyjólfur Reynisson, Arna Vigdís Jónsdóttir, Sigurjón Arason, Maria Eden

Supported by:

EU (contract FP6-016333-2) Chill-on, AVS, R&D Fund of Ministry of Fisheries in Iceland, the Technology Development Fund at the Icelandic Center for Research

Contact

Kolbrún Sveinsdóttir

Project Manager

kolbrun.sveinsdottir@matis.is

The effect of cooling methods at processing and use of gel-packs on storage life of cod (Gadus morhua) loins - Effect of transport via air and sea on temperature control and retail-packaging on cod deterioration

The purpose of the experiments was to investigate the effect of different cooling during processing and temperature fluctuations in transport with and without a cooling mat on the shelf life of cod necks. In processing, it was compared to use no pre-cooling for filleting, liquid cooling and skin cooling (CBC) which is always liquid-cooled. The effect of simulated temperature fluctuations in transport temperature changes (RTS) was compared with storage at a constant temperature (-1 ° C). The effects of using a cooling mat in storage and transport were also assessed. Samples were quality assessed by sensory evaluation, microbial and chemical measurements. Temperature was monitored with thermometers. Skimmed cod fillets in foam plastic boxes were transported to Bremerhaven by air and ship, where they were repackaged in air and aerated packages (MAP) and stored at 1 ° C. Chemical and microbiological measurements were performed to monitor quality changes. The temperature of the erythema necrosis was lower than in the first 2 days of the experiment. The cooling mats had a certain effect of lowering the temperature when temperature fluctuations were in the process and lower temperatures were maintained throughout the storage period. However, the use did not affect the duration of freshness or shelf life according to sensory evaluation. The number of microorganisms was somewhat lower if temperature fluctuations occurred in the process, but there was little difference at a constant temperature. Storage at a constant, low temperature (-1 ° C) prolonged shelf life by approx. 3 days according to sensory evaluation and it was in accordance with microbial counts and measurements of TVB-N and TMA. Experiments in Bremerhaven showed that the number of microorganisms was generally lower when using aerated packaging compared to airborne fish. This was especially noticeable in the flying fish. The fish transported by ship was still stored for as long as the fish transported by air. This is due to the fact that the flying fish experienced greater temperature fluctuations during transport and its surface temperature measured 4 ° C on arrival in Bremerhaven. The transport time by ship was much longer (+48 hours) but the surface temperature was below 2 ° C on receipt. The use of cooling mats had little effect on the temperature during transport, but nevertheless the surface temperature was slightly lower in fish with cooling mats on arrival in Bremerhaven both by air and by ship.

The main aim of the experiment was to investigate the effects of different cooling techniques during processing and temperature fluctuations during transport on the storage life of cod loins with and without gel packs. The following cooling techniques were studied: combined blast and contact (CBC) cooling (with liquid cooling prior to the CBC cooling), only liquid cooling and where no special cooling was used prior to deskinning and trimming. The effect of real temperature simulation (RTS) during storage was compared to a steady storage temperature of -1 ° C. The samples were analyzed with sensory, microbial and chemical methods. The temperature was monitored from packaging using temperature loggers. CBC cooled loins were transported to Bremerhaven via air and ship freight after packaging in EPS boxes. The fish was repacked in air and modified atmosphere and stored at 1 ° C. Deteriorative changes were evaluated by microbial and chemical indicators. CBC cooling resulted in a lower temperature profile the first two days of the experiment. The use of gel packs lowered somewhat the temperature increase in the products when RTS was applied and lower temperature was maintained during the entire storage period. According to sensory evaluation, the use of gel packs did not result in prolonged freshness period or shelf life. According to microbial and chemical analysis no marked difference was seen whether gel packs were used or not in groups stored at a steady temperature. However, microbial counts were somewhat lower and slower formation of TVB-N and TMA occurred in RTS groups where gel packs were used compared to no gel packs. Storage at a steady -1 ° C resulted in extended shelf life of three days according to sensory evaluation. This was confirmed by microbial and chemical analysis as lower microbial counts, TVB-N and TMA values were generally obtained in the steady temperature group than in the group receiving the RTS treatment. The storage studies carried out at Bremerhaven on modified atmosphere vs. air packed loins showed generally lower microbial counts, especially in the air transported fish. Deterioration process of air and sea freight fish was however similar. Re-packaging of sea freight fish at a later stage did not significantly affect its deteriorative process compared to re-packed air freight fish. This might be due to the fact, that the air freight fish was subject to high temperatures during transport and surface temperature reached over 4 ° C. The sea freight fish had a much longer transport phase, but arrived with surface temperatures below 2 ° C. This shows that not only the time of re-packaging but also the temperature profile during transport are important factors influencing the deteriorative process and shelf life. Gel packs did not have significant cooling effect in this experiment. However the surface temperature in boxes with a gel pack was slightly lower than in boxes without a gel pack independently of transport mode used.

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Reports

SSS PREDICTION WORKSHOP

Published:

29/04/2010

Authors:

Paw Dalgaard, Anna Kristín Daníelsdóttir, Steinar B. Aðalbjörnsson

Contact

Anna Kristín Daníelsdóttir

Deputy CEO / Director of Research & Innovation

annak@matis.is

SSS PREDICTION WORKSHOP

Courses in the use of forecasting programs in the fisheries sector: SSS (Seafood Spoilage and Safety) Prediction version 3.1 2009 (http://sssp.dtuaqua.dk/), Combase (www.combase.cc) and Pathogen Modeling programs (http: // pmp .arserrc.gov/PMPOnline.aspx). The teacher is Dr. Paw Dalgaard from the Technical University of Denmark (DTU) and the teaching is in English. The program is useful for scientists, authorities and industry in the fisheries sector.

Workshop on the practical use of computer software to manage seafood quality and safety. It includes presentations and hands-on computer exercises to demonstrate how available software can be used by industry, authorities and scientists within the seafood sector. Examples with fresh fish, shellfish and ready-to-eat seafood (smoked and marinated products) are included in the workshop. Special attention is given to: (i) the effect of storage temperature and modified atmosphere packing on shelf-life and (ii) management of Listeria monocytogens according to existing EU regulations (EC 2073/2005 and EC 1441/2007) and new guidelines from the Codex Alimentarius Commission. The presentations included in the workshop are given in English by Paw Dalgaard from the Technical University of Denmark. Participants will use their own laptop computers for the PC-exercises included in the workshop. Instruction for download of freeware will be mailed to the participants prior to the start of the workshop.

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Reports

The effect of different precooling media during processing and cooling techniques during packaging of cod (Gadus morhua) fillets

Published:

01/04/2010

Authors:

Björn Margeirsson, Hannes Magnússon, Kolbrún Sveinsdóttir, Kristín Líf Valtýsdóttir, Eyjólfur Reynisson, Sigurjón Arason

Supported by:

AVS Fund of Ministry of Fisheries in Iceland, The Technology Development Fund at the Icelandic Center for Research, University of Iceland Research Fund

Contact

Kolbrún Sveinsdóttir

Project Manager

kolbrun.sveinsdottir@matis.is

The effect of different precooling media during processing and cooling techniques during packaging of cod (Gadus morhua) fillets

The purpose of the experiments was to investigate the effect of different refrigerants in pre-cooling before packaging on temperature control, quality and shelf life of cod fillets. The following refrigerants were examined and compared with no special pre-packing pre-packing:

  1. brine with a low salt content, 2) ice cream with a low salt content.

In addition, the effects of using ice mats and dry ice on the storage of the wrecks were investigated. Temperature changes were monitored by temperature sensors at all levels. Samples were quality assessed by sensory evaluation, microbial and chemical measurements for up to 13 days from processing and packaging (16 days from fishing). The fillets were stored in supercooled conditions (below 0 ° C) for most of the storage time. Lower temperatures of slurry ice than brine led to lower fillet temperatures during packing, and the temperature of the liquid brine was found to rise rapidly during processing. Different treatment resulted in a comparable freshness period according to sensory evaluation. However, the use of a liquid brine during pre-packaging pre-packing proved to lead to a shorter shelf life of 1-2 days compared to no pre-cooling or pre-cooling with slush ice. The reasons for this can be traced to the fact that the brine contained a considerable amount of microorganisms, including H2S-producing bacteria which are active producers of trimethylamine (TMA). Comparison of liquid-cooled fillets showed that the use of dry ice prolonged shelf life by 1 day compared to ice mats. The results of microbial and chemical measurements were consistent with these results.

The aim of the experiment was to investigate effects of two cooling media during precooling at processing on temperature control, quality and storage life of cod fillets. The two cooling media compared to no special precooling during processing (NC) were: 1) liquid brine (LC) and 2) slurry ice (SIC). In addition, the influence of using either dry ice or ice packs during storage was studied. The samples were kept at superchilled conditions during most of the trial. The environmental and product temperature history of each group was studied using temperature monitors. The samples were analyzed with sensory evaluation, microbial and chemical methods for up to sixteen days from catch (thirteen days from processing). Lower temperature of the slurry ice than the liquid brine resulted in lower fillet temperature at packaging and the liquid brine temperature increased rapidly during a processing break, which seems to be a weakness of the liquid brine tank. Results from sensory, microbial and chemical analysis all showed that immersing the skinless cod fillets in liquid cooling brine prior to packaging resulted in one to two days reduction of shelf life in comparison with fillets that were not immersed in liquid brine (no cooling) or in slurry ice. This could be attributed to the fact that the cooling brine carried considerable amounts of microbes including H2Sproducing bacteria which are active producers of trimethylamine (TMA). Comparison of the groups receiving liquid cooling showed that dry ice appeared to extend the shelf life of one day as compared to ice packs. The length of the freshness period was, however, similar in all experimental groups according to sensory evaluation. These results were confirmed by total volatile bases (TVB-N) and TMA analysis and microbial counts.

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Reports

Optimal storage conditions for fresh farmed tilapia (Oreochromis niloticus) fillets

Published:

01/12/2009

Authors:

Emilia Martinsdóttir, Cyprian Ogombe Odoli, Hélène L. Lauzon, Kolbrún Sveinsdóttir, Hannes Magnússon, Sigurjón Arason, Ragnar Jóhannsson

Supported by:

Technology Development Fund

Contact

Kolbrún Sveinsdóttir

Project Manager

kolbrun.sveinsdottir@matis.is

Optimal storage conditions for fresh farmed tilapia (Oreochromis niloticus) fillets

The purpose of the experiments was to find the best storage conditions for fresh tilapia fillets by determining the shelf life by sensory evaluation, microbial counts and physical and chemical measurements. Nile tilapia (Oreochromis niloticus) raised in a renewable water cycle system was filleted and packed in 100% air and aerated packages 50% CO2: 50% N2 MA for storage at 1˚C and -1˚C. The development of the QIM rating scale and the sensory evaluation properties of fresh and cooked tilapia fillets and the use of the scale in shelf life testing are described. A linear relationship was found between the quality factor and the storage time (r> 0.93) for all storage groups. The results of sensory evaluation and microbial counts showed that fillets packed in air had a shelf life of 13-15 days at 1˚C and 20 days at -1˚C. At the end of shelf life in air packs, the total number of micro-organisms and the number of pseudomonads micro-logs were 7 CFU / g in meat. In fillets in aerated packages, the coating phase was longer and the total number of microorganisms was below log 4 CFU / g after 27 days of storage at both 1˚C and -1˚C. However, aerobic conditions adversely affected the color of the fillets shortly after packing, but the color of the fillets significantly affected buyers' choices. Chemical measurements such as TVB-N and TMA were not a good measure of damaged fillet fillets. The best storage conditions for tilapia fillets are air packing and storage at a constant low temperature of -1 ° C. This report is based on the main findings of Cyprian Ogombe Odoli's master's project.

The main aim was to establish optimal storage conditions for fresh tilapia fillets by determining its shelf life by sensory and microbiological evaluation, as well as monitoring its physical-chemical properties. Nile tilapia (Oreochromis niloticus) farmed in recirculation aquaculture system was filleted and packaged in 100% air and 50% CO2: 50% N2 MA prior to storage at different temperature; 1˚C and -1˚C. This report further describes the development of a Quality Index Method (QIM) scheme and a sensory vocabulary for fresh and cooked tilapia fillets accordingly and application in a shelf life study. The application of the QIM scheme for tilapia fillets showed a linear relationship between QIM scores and storage time (r> 0.93) for all samples. The results from sensory analysis of cooked samples as well as microbial growth indicated that fillets packaged in 100% air had a shelf life of 13-15 days during storage at 1˚C and 20 days during storage at -1˚C. At the end of shelf life in 100% air packaged groups, TVC and pseudomonads counts reached log 7 CFU / g in flesh. In MA packaged fillets, the lag phase and generation time of bacteria was extended and recorded total counts below the limit for consumption (<log 4 CFU / g) up to 27 days of storage at both 1˚C and -1˚C. However, MA packaging negatively affected the color characteristics of the fillets soon after packaging (as from d6) but color is an important indicator of quality and a major factor in influencing retail purchase decisions. Chemical analyzes (TVB-N and TMA) were not good indicators of spoilage of tilapia fillets in the present study. 100% air packaging at -1˚C storage temperature is the optimal storage conditions for fresh tilapia fillets. The report is based on the master thesis of Cyprian Ogombe Odoli.

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Reports

Injection and brining of tilapia fillets

Published:

01/12/2009

Authors:

Kristín Anna Þórarinsdóttir, Kolbrún Sveinsdóttir, Þóra Valsdóttir, Irek Klonowski, Aðalheiður Ólafsdóttir, Hannes Magnússon, Arnljótur Bjarki Bergsson, Ragnar Jóhannsson, Emilia Martinsdóttir

Supported by:

Tækniþróunarsjóður Rannís / Technology Development Fund, RANNIS - Icelandic Center for Research

Contact

Kolbrún Sveinsdóttir

Project Manager

kolbrun.sveinsdottir@matis.is

Injection and brining of tilapia fillets

The aim of the project was to investigate the effect of spraying and pickling on the utilization, shelf life and properties of tilapia fillets. Three product categories were produced: chilled products, frozen products (with insignificant changes in salt content) and lightly salted, frozen products. During the processing of chilled products, red fillets were injected with a weak brine (1% salt) containing a reduced cod base (2% brine protein). Lightly salted fillets were initially sprayed with 4% brine, then pickled overnight. Part of the fillet was frozen after pickling but a similar amount was injected with the protein solution after pickling. Utilization increased during spraying and pickling, there was a significant difference in weight changes in frozen fillets and lightly salted fillets due to differences in the salt content of these two product categories. The waterproofness of fillets was poorer after freezing than after storage in the refrigerator. The shelf life of products was short and possible reasons for this are discussed in the report. Microbial growth and degradation processes were largely independent of injection and brine.

The objective of the project was to study effect of injection and brining on the yield, storage life and characteristics of tilapia fillets. Three different product groups were produced: chilled. Frozen (with small salt changes) and lightly salted products. During processing of chilled products fillets with skin were injected with brine containing minced cod (2%) protein in brine. Lightly brined fillets were initially injected with 4% brine and then brined overnight. A part of the fillets was frozen after brining but similar part was injected with protein solution after brining. The yield increased with injection and brining, distinct difference was in the weight changes of frozen and lightly salted fillets because of the difference of the salt content of these two product groups. Water holding capacity of the frozen fillets was lower than for chilled fillets and the storage life was very short. Microbial growth was mostly not depending on the injection and brining.

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Reports

The effect of liquid cooling at processing and different cooling techniques during transport of cod (Gadus morhua) fillets

Published:

01/11/2009

Authors:

Hannes Magnússon, Lárus Þorvaldsson, Kolbrún Sveinsdóttir, Hélène L. Lauzon, Kristín Anna Þórarinsdóttir, Sigurjón Arason, Emilia Martinsdóttir

Supported by:

AVS R&D Fund of Ministry of Fisheries in Iceland, the Technology Development Fund at the Icelandic Center for Research and EU (contract FP6-016333-2)

Contact

Kolbrún Sveinsdóttir

Project Manager

kolbrun.sveinsdottir@matis.is

The effect of liquid cooling at processing and different cooling techniques during transport of cod (Gadus morhua) fillets

The purpose of the experiments was to investigate the effect of different refrigeration techniques and the effect of temperature fluctuations on the quality and shelf life of cod fillets. The following cooling technology was investigated: Liquid cooling in brine during processing based on no cooling and the effect of temperature fluctuations during storage compared to a constant temperature (-1 ° C). In addition, the effects of using ice mats and dry ice on the storage of the wrecks were investigated. Temperature changes were monitored by temperature sensors at all levels. Samples were quality assessed by sensory evaluation, microbial and chemical measurements for up to 14 days from fishing (11 days from processing and packaging). Different treatment resulted in different freshness times and shelf life according to sensory evaluation. Groups that were liquid-cooled during processing had a shelf life of about 2-3 days shorter than fillets that were not cooled in this way. The reasons for this can be traced to the fact that the cooling brine contained a considerable amount of microorganisms, including the destructive bacterium Photobacterium phosphoreum, which is a very active producer of trimethylamine (TMA). Comparison of liquid-cooled fillets showed that the use of dry ice prolonged shelf life by 1-2 days compared to ice mats. Storage at -1 ° C did not have a significant effect on freshness time and shelf life compared to fillets where temperature fluctuations were applied according to sensory evaluation. The results of microbial and chemical measurements were consistent with these results.

The aim of the experiment was to investigate the effects of different cooling techniques and temperature fluctuations on the storage life of cod fillets. The following cooling techniques were studied: liquid cooling in brine at plant as compared to no special cooling at processing. The effect of real temperature (RTS) simulation during storage was compared to a steady storage temperature at -1 ° C. Additionally, the influence of using either dry ice or ice packs during storage was studied. The temperature history of each group was studied using temperature loggings. The samples were analyzed with sensory evaluation, microbial and chemical methods for up to 14 days from catch (11 days from packaging). The different treatments of the groups resulted in different lengths of freshness period and maximum shelf life according to sensory evaluation. Liquid cooling resulted in a 2-3 days shorter maximum shelf life than the group that was not receiving liquid cooling. This could be attributed to the fact that the cooling brine carried considerable amounts of microbes including the spoilage bacterium Photobacterium phosphoreum which is an active producer of trimethylamine (TMA). Comparison of the groups receiving liquid cooling showed that dry ice appeared to extend the shelf life of 1-2 days as compared to ice packs. Storage at -1 ° C did not have much influence on the freshness period or maximum shelf life. These results were confirmed by total volatile bases (TVB-N) and TMA analysis and microbial counts.

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Reports

The effect of different cooling techniques and temperature fluctuations on the storage life of cod fillets (Gadus morhua)

Published:

01/08/2009

Authors:

Hannes Magnússon, Hélène L. Lauzon, Kolbrún Sveinsdóttir, Björn Margeirsson, Eyjólfur Reynisson, Árni Rafn Rúnarsson, María Guðjónsdóttir, Kristín Anna Þórarinsdóttir, Sigurjón Arason, Emilía Martinsdóttir

Supported by:

AVS R&D Fund of Ministry of Fisheries in Iceland, the Technology Development Fund at the Icelandic Center for Research and EU (contract FP6-016333-2)

Contact

Kolbrún Sveinsdóttir

Project Manager

kolbrun.sveinsdottir@matis.is

The effect of different cooling techniques and temperature fluctuations on the storage life of cod fillets (Gadus morhua)

The purpose of the experiments was to examine two refrigerants on board a fishing vessel, to use different refrigeration techniques during processing, including so-called CBC (combined blast and contact) refrigeration and to examine the effect of temperature fluctuations during storage compared to continuous storage at -1 ° C. There was little difference in microbial and chemical measurements, whether plate ice or liquid ice was used for processing, but according to sensory evaluation, the group that was cooled with liquid ice had one day longer freshness and shelf life. The temperature was usually slightly higher in the group as plate ice was used for processing during the storage period. According to sensory evaluation, microbial counts and chemical measurements, CBC cooling proved to be the best for prolonging freshness and shelf life. Temperatures were found to be lower in the groups where CBC cooling was used. The number of microorganisms was similar in the two groups where CBC cooling was not used in the processing (liquid cooling and no cooling). These results were consistent with the results of sensory evaluation. TMA levels were slightly higher on storage days 12-19 in the liquid-cooled group. The results of temperature measurements during the storage period were similar. A similar number of microorganisms were found to be in groups stored at a constant temperature (about -1 ° C) on the one hand and in groups where temperature fluctuations were applied during the first part of the storage period on the other hand. During the first 15 days of storage, TVB-N and TMA values were found to be similar in the groups. The groups stored at a constant temperature did not undergo sensory evaluation. Microbial assays performed by the fast-acting method qPCR were in good agreement with culture methods for Pseudomonas spp. and Photobacterium phosphoreum.

The purpose of this experiment was to examine two different cooling methods on board fishing vessel, to apply different cooling techniques during processing at fish plant including the CBC (combined blast and contact) cooling and to compare storage of packed cod fillets kept either at steady temperature (-1 ° C) or below temperature fluctuations. No marked difference was seen in microbial and chemical measurements whether plate ice or liquid ice was used prior to filleting but according to sensory analysis, the experimental group where liquid ice was used had one day extension in freshness and shelf life compared to the group with plate ice. Temperature was usually slightly higher in the plate ice group than the liquid ice group during storage. According to sensory, microbiological and chemical analysis, the CBC cooling clearly resulted in longer freshness period and shelf life extension in comparison to the two groups where this technique was not applied during processing. Temperature was lower in these groups during the storage period. Similar microbial counts were found between the two experimental groups where CBC was not applied during processing (liquid cooling and no cooling). These results were in agreement with results from sensory analysis. TMA values were however higher on storage days 12 to 19 in the group with liquid cooling. Temperature measurements during storage of these two groups were very similar. No marked difference was seen in microbial counts between groups that were stored at a constant temperature around -1 ° C compared to groups where temperature fluctuations were used during early phases of storage. During the first 15 days of storage, TVB-N and TMA values were very similar for these groups. Sensory analysis was not done on the two groups kept at -1 ° C. The rapid qPCR analysis was generally in good agreement with the cultivation methods for Pseudomonas spp. and Photobacterium phosphoreum.

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Reports

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

Published:

01/09/2008

Authors:

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

Supported by:

AVS Research Fund, Rannís Technology Development Fund

Contact

Kolbrún Sveinsdóttir

Project Manager

kolbrun.sveinsdottir@matis.is

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

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

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

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