Tag: Microorganisms

Reports

Microorganisms for aquaculture sludge enrichment   

Published:

21/12/2023

Authors:

Anna Berg Samúelsdóttir, Matís, Alexandra Leeper, Sjávarklasinn, Clara Jégousse, Sjávarklasinn, Ólafur H. Friðjónsson, Matís, Elísabet Eik Guðmundsdóttir, Matís, Hörður Guðmundsson, Matís and Birgir Örn Smárason, Matís

Supported by:

Hringrásarsjóður

Contact

Anna Berg Samúelsdóttir

Project Manager

annab@matis.is

The main goal of the project "Microbes for the enrichment of aquaculture sludge" was to develop a method for treating side streams from aquaculture (sludge) with microorganisms so that the sludge can be used as fertilizer for agriculture.  

Considering the rapid growth of aquaculture in Iceland, it is crucial for the sustainability of the industry to find solutions for side currents and thus strengthen the circular economy. The implementation of solutions that promote the use of side streams, and promote circulation, are in line with the United Nations' goals for sustainable development. 

The legal framework for the use of fish farm sludge as fertilizer is both extensive and in parts quite complex, i.e. what is allowed and who grants permission. As an example of the requirements for using sludge as fertilizer, sludge must be applied to the pasture before December 1st if the area is to be used for grazing, animals can then be grazed on the area 5 months later or on April 1st at the earliest.  

In the project, work was done to enrich nitrate in the sludge with microorganisms to increase the possibility of using the sludge as a fertilizer. An enrichment culture was established with the aim of enriching ammonia-oxidizing bacteria in the sludge. A chemical analysis of the sludge was also carried out to assess its nutrient content. The results of chemical measurements indicate that sludge can be ideal as a supplement or additive to, for example, biodegradable livestock manure. It is important to continue with a project that contributes to increasing the value of by-products such as sludge in order to keep nutrients within the circular economy. The use of sludge as fertilizer is beneficial for both aquaculture companies and Icelandic agriculture.  
_____

The primary objective of the project "Microorganisms for aquaculture sludge enrichment" was to develop a method for treating side streams from aquaculture (sludge) using microorganisms, thereby rendering the sludge suitable for use as agricultural fertilizer. 

Given the rapid expansion of aquaculture in Iceland, finding solutions for side streams is imperative to sustain the industry and enhance circular economy practices. Implementing solutions that encourage side stream utilization aligns with the United Nations' sustainable development goals. 

The legal landscape for utilizing fish farm sludge as fertilizer is extensive and, in certain aspects, complex, delineating what is permissible and who grants permission. For instance, applying sludge to pasture for grazing requires adherence to specific timelines, such as application before December 1st, with grazing permitted no earlier than 5 months later or on April 1st. 

The project focused on enriching the sludge's nitrogen content with microorganisms. An enrichment culture was established to promote ammonia-oxidizing bacteria in the sludge, increasing its potential as a fertilizer. Chemical analysis of the sludge was conducted to evaluate its nutrient content. The results indicate that the sludge can serve as an ideal supplement or additive, for instance, with biodegradable livestock manure. Continuing projects that enhance the value of like sludge is crucial for maintaining nutrient cycles within the circular economy. The use of sludge as fertilizer is mutually beneficial for both aquaculture companies and Icelandic agriculture. 

View report

Reports

Microbial diversity in the Icelandic fishing grounds

Published:

01/12/2011

Authors:

Eyjólfur Reynisson, Sveinn Haukur Magnússon, Árni Rafn Rúnarsson, Kristinn Guðmundsson, Erla Björk Örnólfsdóttir, Viggó Þór Marteinsson

Supported by:

Fisheries Project Fund

Contact

Viggó Marteinsson

Research Group Leader

viggo@matis.is

Microbial diversity in the Icelandic fishing grounds

The diversity of microorganisms in the ocean around Iceland is largely unknown, but little or no research has been done to date. In this study, samples of the sea around the country were collected for analysis of microbial concentrations by flow cytometry and their diversity using molecular biological methods. A total of 504 sea samples were collected; 483 samples from the MRI's spring rally, 16 samples from Breiðfjörður and 5 samples were collected north of the Westfjords with specially equipped bottom trawling equipment. From the spring rally, selected samples were further investigated, they came from Selvogsbanki, Siglunes and Langanes as well as each sample west of Látrabjarg and Hornbanki. The microbial concentration was highest in Selvogsbanki, where the total count was about 1.6 million cells / mL of seawater. However, the calculated mean of all samples was 0.68 million cells / mL. The species composition of the microflora was determined by amplification and sequencing of the 16S bacterial gene. A total of 528 sequences were sequenced showing 174 different 16S bacterial sequences in the samples and 52% were found to belong to previously unknown bacterial species. The diversity of the microbial flora was generally high, with the exception of trawl tails. Eight batches of bacteria were detected in the samples to varying degrees. Cyanobacteria and Cyanobacteria-like sequences were predominant in all samples except for the 353-0m sample at Selvogsbanki, where their proportion was only 4%. Alpha and Gamma ‐ protebacteria predominated there. Of the other groups, Flavobacteria was regularly diagnosed together with other groups in a smaller proportion. Differences in the microbial composition of marine samples were assessed using a key factor analysis of the fingerprints of microbial communities obtained using t-RFLP technology. Overall, the main difference was in samples from each sample cycle, ie. from vorralli, Breiðafjörður and the tail of a trawler. The variability within the samples from the spring rally went hand in hand with the sampling point where samples from Selvogsbanki showed greater mutual similarity compared to the samples north of Siglufjörður and west of Iceland which were more different from each other. Data from the fingerprints of microbial communities in different samples showed a correlation between certain variables in the fingerprints of the communities with environmental factors that were measured during the sampling. Temperature had the most to say but also fluorescence and salinity. Vibrio was screened. Paramaemolyticus in warm seawater samples from the south of the country where the sea surface temperature was between 8-10 ° C. No V. parahaemolyticus was detected in these samples. The results of this project can be regarded as an important basis for further research on microorganisms in Icelandic waters. Ongoing research in this field can be of great significance in the long term to assess the impact of foreseeable environmental changes due to global warming on marine life and fish stocks in Icelandic waters. 

The diversity of microorganisms in the ocean around Iceland is largely unknown and little or no research has been conducted to date. In this study, seawater samples around the country were gathered for analysis concentration and diversity of microorganisms using flow ‐ cytometry and molecular methods. A total of 504 samples were collected. All samples were analyzed with regards to microbial counts while samples from selected areas were investigated further, from Selvogsbanki, Siglunes and Langanes. Microbial concentrations were highest at Selvogsbanki, where the total counts were around 1.6 million cells / ml. Arithmetic mean of all samples was o.68 million cells / ml. Species composition of microbial flora was determined by amplification and sequencing of the 16S bacterial gene. A total of 528 16S sequences were sequenced, and showed 174 different bacterial sequences. 52% of the sequences belonged to previously unknown bacterial species. Eight divisions of bacteria were detected in the samples. Cyanobacteria and cyanobacteria ‐ like sequences were predominant in all samples except sample 353‐0m in Selvogsbanki where the ratio was only 4% and alpha and gamma‐ proteobacteria were predominant. Of other ranks identified, Flavobacterium were regularly detected along with other less frequent groups. The difference in microbial composition in the sea samples was assessed by principal component analysis of the microbial community fingerprint obtained by t ‐ RFLP technique. Variability within the samples was dependent upon sampling point, samples from Selvogsabanki showed more correlation with other samples from that area - than with samples from Siglunes or the west coast of Iceland that showed more intrinsic diversity. The community fingerprint and changes in the fingerprint shows correlation to changes in environmental factors measured at sampling. Temperature was the most important environmental factor, along with fluorescence and salinity. Samples from the warmer waters off the south coast were screened for Vibrio parahaemolyticus, but none was detected. The results of this project can be seen as an important basis for further studies of microorganisms in Icelandic waters. Continued research in this area can be of great importance for the evaluation environmental change and the effects of global warming on the marine environment and exploitable marine species in Icelandic waters.  

View report

Reports

Microbial density in Icelandic waters

Published:

01/12/2011

Authors:

Eyjólfur Reynisson, Sveinn Haukur Magnússon, Viggó Þór Marteinsson

Supported by:

Fisheries Project Fund

Contact

Viggó Marteinsson

Research Group Leader

viggo@matis.is

Microbial density in Icelandic waters

The diversity of microorganisms in the ocean around Iceland is largely unknown, but little or no research has been done to date. This report describes the first comparative results from a study on the microbial diversity of the ocean around the country. Sea samples around the country were collected in the spring of 2010 and 2011. The density of microorganisms in these samples has now been examined by microbial flow analysis and comparisons made by depth, location and between years. The results show that the diversity varies from region to region. The sea to the south of the country generally shows 40-60% more microbial density than the sea to the north of the country. Variability is also seen in the growth of algae or algae flowers. The results are the basis for further research into the microbial composition and diversity of the ocean around the country - which is already underway within the project.

The diversity of microorganisms in the ocean around Iceland is largely unknown and little or no research has been conducted to date. This report describes the first comparative results of microbial diversity in the sea around the country. Sea ‐ samples around the country were collected in the spring of 2010 and 2011. The density of microorganisms in these samples was studied by flow cytometry and comparisons made by the depth, location and year. The results show that diversity varies by region. The sea south of the country has approximately 40‐60% higher microbial density than the sea north of the country. Variation is also seen in relation to the growth of algae or algal blooms. These results are the basis for further research on the microbial composition and diversity of the sea around the country - already underway within project. 

Report closed until 01.01.2014 / Report closed until 01.01.2014

View report

Reports

Compilation of previous test results of capelin roes / Compilation of previous test results of capelin roes

Published:

01/02/2009

Authors:

Margeir Gissurarson, Hannes Magnússon, Ragnheiður Sveinþórsdóttir, Cecilia Garate

Supported by:

AVS Research Fund

Contact

Margeir Gissurarson

Strategic Scientist

margeir.gissurarson@matis.is

Compilation of previous test results of capelin roes / Compilation of previous test results of capelin roes

In recent years and decades, various measurements and research on capelin roe in Iceland have been carried out at Matís ohf / Rannsóknastofnun fiskiðnaðarins. This is primarily a study of microorganisms, egg filling and water content. The report will cover microbial research carried out during the 1984 season, microbiological measurements in the period 2000-2008 and measurements of water content and egg filling 1984-2008.

In recent years and decades various studies and measurements have been carried out on capelin roes in Iceland at Matís ohf / Icelandic Fisheries Laboratories. They mainly include studies on microorganisms, roe-fill and water content. In this report, microbial studies on microorganisms from the capelin season 1984 are presented along with microbial measurements carried out during 2000-2008 and measurements of roe-fill and water content 1984- 2008.

View report

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.

View report

Reports

Shelf life tests on cod pieces: Effects of supercooling on salt and protein injected cod muscles

Published:

01/12/2007

Authors:

María Guðjónsdóttir, Kolbrún Sveinsdóttir, Hannes Magnússon, Sigurjón Arason

Supported by:

Rannís Research Fund

Contact

Kolbrún Sveinsdóttir

Project Manager

kolbrun.sveinsdottir@matis.is

Shelf life tests on cod pieces: Effects of supercooling on salt and protein injected cod muscles

An integrated refrigeration study was performed on the effects of salting, protein injection and subcooling on the quality, chemical and physical properties of salt and protein injected cod muscles. The study shows that by injecting salt and protein into the muscle, utilization can be improved, drip reduced and the boiling efficiency of the muscle increased. On the other hand, the injection of salt and protein into muscles increases microbial growth and the formation of erratic alkalis, thus shortening the shelf life of the product. However, lowering the storage temperature could inhibit the growth of microorganisms and the formation of erratic alkalis. Decreased storage temperature, however, led to cell damage due to ice formation on the surface regardless of the salinity of the muscle. Therefore, it is not considered desirable to store fresh or lightly salted cod muscle at temperatures below -2 ° C. The effect of rinsing the samples in a brine bath after injection was also investigated. Such rinsing did not significantly affect the water and salinity or efficiency of the samples, but showed a reduction in the formation of erratic bases. It is therefore advisable to rinse fillets in brine after injection to prevent damage to the best extent possible. Sensory evaluation results showed that the properties of the muscle changed significantly with the injection of salt and protein into the muscle, but the injected groups lost their freshness characteristics until the fresh untreated control group.

A combined cooling experiment was performed on the effect of salting, protein injection and superchilling on the quality and physicochemical properties of brine and protein injected cod muscle. The study showed that brine and protein injections lead to increased processing and cooking yield, as well as decreased drip. Injection of salt and proteins increase on the other hand microbiological growth and the formation of volatile nitrogen bases, which in turn leads to shorter shelf life. By lowering the storage temperature this growth of microorganisms and volatile nitrogen bases could be decreased. If the storage temperature is kept too low this on the other hand led to cell damages due to ice crystallization on the muscle surface, independent on the salt content of the muscle. It is therefore not recommended to store fresh and light salted cod at temperatures below -2 ° C. The study also viewed the effect of brining the muscle after brine and protein injection. This brining had no significant effect on the salt or water content of the muscle but decreased the amount of volatile bases. It is therefore recommended that cod muscle is always washed in brine after injection to keep damaging processes at a minimum. Sensory analysis showed a significant difference between the characteristics of brine and protein injected samples to unprocessed cod muscle. The injected groups also lost their freshness characteristics earlier than the unprocessed control group.

View report

Reports

Dried fish as health food

Published:

01/09/2007

Authors:

Ásbjörn Jónsson, Guðrún Anna Finnbogadóttir, Guðjón Þorkelsson, Hannes Magnússon, Ólafur Reykdal, Sigurjón Arason

Supported by:

AVS Research Fund, (AVS-Fund)

Contact

Guðjón Þorkelsson

Strategic Scientist

gudjon.thorkelsson@matis.is

Dried fish as health food

One of the main goals of the project was to obtain basic information about the properties of Icelandic dried fish and that the information would be open and thus for the benefit of all dried fish producers in Iceland. The main conclusion of the project is that dried fish is a very rich protein source with 80-85% protein content. The amino acids were measured and compared with amino acids in eggs. The result is that dried fish proteins are of high quality. These results support the marketing of dried fish as both a healthy food and a national food. It is important to look at the salt content in dried fish better and try to reduce it to increase the health of dried fish, especially in hot-dried dried fish, as it was much higher than in other dried fish. Measurements of trace elements showed that their amount in dried fish is well within limits compared to the recommended daily allowance (RDS) except in selenium. Its amount in 100 g is three times the recommended daily dose. However, it is not considered harmful in any way.

The main object of this project was to provide information of the quality in Icelandic dried fish to be of benefit for all producers in Iceland. The main results showed that dried fish was a very rich source of proteins, containing 80-85% protein. Amino acids were measured and compared to the amino acids in eggs. It was concluded that the proteins in the dried fish were of high quality. This supports the marketing of dried fish in the health foods and traditional food markets. It is important to better analyze the salt content in dried fish and reduce it to improve balanced diet in dried fish, especially for indoor produced dried fish, which salt content is rather high. The trace elements in dried fish showed minimal content, except for selen where the content was threefold the recommended daily allowance (RDA). This is not hazardous for people in any way.

View report

Reports

Dried fish as a health food

Published:

01/05/2007

Authors:

Ásbjörn Jónsson, Guðrún Anna Finnbogadóttir, Guðjón Þorkelsson, Hannes Magnússon, Ólafur Reykdal

Supported by:

AVS Fisheries Research Fund

Contact

Guðjón Þorkelsson

Strategic Scientist

gudjon.thorkelsson@matis.is

Dried fish as a health food

The main goal of the project was to obtain basic information about the properties of Icelandic dried fish and that the information would be open and thus to the benefit of all dried fish producers in Iceland. The main conclusion of the project is that dried fish is a very rich protein source with 80-85% protein content. The amino acids were measured and compared with amino acids in eggs. Dried fish proteins proved to be of high quality. These results support the marketing of dried fish, both as a healthy and national food. It is important to look at the salt content of dried fish better and try to reduce it to increase the health of dried fish, especially in hot-dried dried fish as it turned out to be much higher than in other dried fish. Measurements of trace elements showed that their amount in dried fish is well within limits compared to the recommended daily allowance (RDS) outside selenium. Its amount in 100 g is three times the recommended daily dose. However, it is not considered harmful in any way.

The main object of this project was to establish information of the quality of Icelandic dried fish, which could benefit producers in Iceland. The main results showed that dried fish is a very rich source of proteins, containing 80-85% protein. Amino acids were measured and compared with amino acids in eggs. The conclusion was that proteins in the dried fish were of high quality. This supports the marketing of dried fish in the health foods and traditional food markets. However, it is important to analyze better the salt content in dried fish and find ways to reduce it to improve balanced diet in dried fish, especially for indoor produced dried fish, where the salt content is rather high. The trace elements in dried fish were found to be minimal, except for selen, where the content was threefold the recommended daily allowance (RDA). This is not, however, hazardous for people in any way.

View report

Reports

Shelf life tests on cod pieces: Effect of supercooling, pickling and gas packaging on quality changes and shelf life / Storage trials on cod loins: Effect of superchilling, brining and modified atmosphere packaging (MAP) on quality changes and sensory shelf-life

Published:

01/05/2007

Authors:

Hannes Magnússon, Hélène L. Lauzon, Kolbrún Sveinsdóttir, Ása Þorkelsdóttir, Birna Guðbjörnsdóttir, Emilia Martinsdóttir, Guðrún Ólafsdóttir, María Guðjónsdóttir, Sigurður Bogason, Sigurjón Arason

Supported by:

AVS Fisheries Research Fund, Technology Development Fund (Rannís)

Contact

Kolbrún Sveinsdóttir

Project Manager

kolbrun.sveinsdottir@matis.is

Shelf life tests on cod pieces: Effect of supercooling, pickling and gas packaging on quality changes and shelf life / Storage trials on cod loins: Effect of superchilling, brining and modified atmosphere packaging (MAP) on quality changes and sensory shelf-life

The aim of these experiments was to evaluate the effect of supercooling, aerated packaging (MAP) and brine on quality changes and shelf life of cod pieces. The effects of gas packaging and different storage temperatures on the growth of several pathogens and pointing organisms were also investigated. The experiment was carried out in October 2006 at Samherji in Dalvík. After storage (0.6 and 2% salt), the fish was trimmed and the neck pieces were packed in standard 3 kg foam packs (air packs) and in air-conditioned packaging. The gas mixture was adjusted to 50% CO2, 5% O2 and 45% N2. Three pieces (350- 550g) were placed in each tray with a drying mat. After packing, the samples were placed in Matís freezer simulators set at 0 ° C, -2 ° C and -4 ° C. The samples were examined over a four-week storage period. Sensory evaluation, microbial counts and chemical measurements were used to assess quality changes and shelf life. Pickled (2% salt) fish were stored shorter than uncooked (0.6% salt). A comparison of the number of micro-organisms the day after packing showed that the pickled fish contained ten times more cold-resistant micro-organisms than the non-pickled ones. According to sensory evaluation, the shelf life of the pickled fish at -2 ° C was 12-15 days in both air- and gas-packed pieces. In the blunt fish, the effects of gas packaging and supercooling were evident. The shelf life of air-packed pieces was about 11 days at 0 ° C and 14-15 days at -2 ° C. The shelf life of gas-packed pieces, on the other hand, was about 15 days at 0 ° C and about 21 days at -2 ° C. Supercooling of fresh uncooked fish products in air-conditioned packaging can therefore significantly increase shelf life. Gas packing significantly reduced the growth rate of pathogens and microorganisms at low temperatures. Salmonella was most affected, then Escherichia coli and Listeria monocytogenes the least. Under air conditions, L. monocytogenes grew at -2 ° C, but E. coli began to multiply at 5 ° C and Salmonella at 10 ° C.

The aim of these experiments was to evaluate the effect of superchilling, modified atmosphere packaging (MAP) and brining on the quality changes and sensory shelf-life of cod loins. The effect of MAP and different storage temperatures on some pathogenic and indicator bacteria was also tested. These experiments were initiated in October 2006 at Samherji, Dalvík. After brining (0.6 and 2% salt) the fish fillets were trimmed, and loins packed on one hand in 3 kg styrofoam boxes (air) and on the other in MA. The gas mixture used was 50% CO2, 5% O2 and 45% N2. Three pieces (350-550 g) were placed in each tray with an absorbent mat. After packaging the samples were placed in 3 coolers at Matís which were adjusted to 0 ° C, -2 ° C and -4 ° C. Samples were examined over a four-week period. Sensory analysis, microbial counts and chemical measurements were used to determine the quality changes and shelf-life. Brined loins had a shorter shelf-life than unbrined (0.6% salt). Comparison on numbers of microorganisms the day after packaging revealed that the brined pieces contained ten times more microbes than the unbrined ones. According to sensory analysis the shelf-life of the brined loins at -2 ° C was 12-15 days for both air- and MA-packed fish. In the unbrined loins the effects of superchilling and MAP were obvious. The shelf-life of air-packed loins was about 11 days at 0 ° C and 14-15 days at -2 ° C. The shelf-life of MA-packed loins was about 15 days at 0 ° C but 21 days at -2 ° C. Superchilling of unbrined fish under MA can therefore increase the keeping quality considerably. MA packaging clearly decreased the growth rate of pathogenic and indicator bacteria at low storage temperatures. Most effects were seen with Salmonella, then Escherichia coli but least with Listeria monocytogenes. In fact, L. monocytogenes could grow at -2 ° C under aerobic conditions, while proliferation of E. coli was first observed at 5 ° C but 10 ° C for Salmonella.

View report
EN
IS EN