Tag: Microstructure

Reports

Comparison of microstructure between farmed and wild cod

Published:

01/12/2008

Authors:

Valur Norðri Gunnlaugsson, Guðrún Anna Finnbogadóttir

Supported by:

AVS R26-06 / AVS R&D Fund of Ministry of Fisheries in Iceland

Contact

Valur Norðri Gunnlaugsson

Research Group Leader

valur.n.gunnlaugsson@matis.is

Comparison of microstructure between farmed and wild cod

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

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

Report closed until December 2011 / Report closed until December 2011

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Reports

Improved quality of herring for human consumption

Published:

01/12/2007

Authors:

Ásbjörn Jónsson, Hannes Hafsteinsson, Irek Klonowski, Valur N. Gunnlaugsson

Supported by:

Nordic Innovation Center

Contact

Valur Norðri Gunnlaugsson

Research Group Leader

valur.n.gunnlaugsson@matis.is

Improved quality of herring for human consumption

Herring is one of the most important fish species in the North Atlantic and the Baltic Sea. Although a large part of the catch goes to human consumption, about 85% of herring is processed into fish oil and flour. There is a general desire to increase the consumption of herring for human consumption. It was important to study the different factors that affect the quality of herring and especially how they are controlled by biological conditions. The main reason for the quality problems in herring is the high content of compounds that promote development, and affect the color and texture changes, as well as the loss of nutrients. Better quality results in increased competition for herring production in the Nordic countries, as well as a positive consumer attitude towards herring products. The main goal of the project was to improve the quality and quantity of herring, for consumption, by researching the quality of the raw material after fishing. Emphasis was placed on quality immediately after fishing and the quality of the raw material after varying periods of frost. Factors such as fishing location and fishing time did not affect the quality of the herring. However, freezing at -20 ° C had a significant effect on the quality of the raw material.

Herring is one of the most important fish species in the North Atlantic and Baltic Sea, with an annual catch exceeding 2 million tonnes. Although a large part of these fish is used for human consumption, as much as 85% of the herring is used for industrial production of fish meal and fish oil. There is a general wish to increase the utilization of herring for human consumption. Thus, it was important to study the various parameters which influence the quality of herring, and in particular how these paramenters are controlled by biological factors. A major reason behind quality problems arising during post-harvest handling of herring is its high content of compounds that efficiently catalyzes the development of rancidity, pigmentation, texture changes and loss of nutritional value. Improved quality will result in increased competitiveness of the Nordic fish processing industry and would improve the attitude among consumers towards herring products. The general objective of the project was to improve the quality and quantity of herring to be used for food production by investigating how natural variation in raw material characteristics affects post-harvest quality. Attention was given to the quality immediately after landing and the quality after period of frozen storage. The results indicated no clear differences in the quality of herring regarding catching place or season. The frozen storage for a prolonged time had the major influence on the quality of herring fillets.

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Reports

Effect of high pressure processing in reducing Listeria spp. and on the textural and microstructural properties of cold smoked salmon (CSS)

Published:

01/08/2007

Authors:

Hannes Hafsteinsson, Ásbjörn Jónsson, Valur Norðri Gunnlaugsson, Birna Guðbjörnsdóttir, Magnús Guðmundsson

Supported by:

Icelandic Research Center Research Fund

Contact

Valur Norðri Gunnlaugsson

Research Group Leader

valur.n.gunnlaugsson@matis.is

Effect of high pressure processing in reducing Listeria spp. and on the textural and microstructural properties of cold smoked salmon (CSS)

The main objective of the project was to investigate the effect of hypertension (400-900 MPa) on the death of the bacterium Listeria monocytogenes and quality factors (image structure, texture and color) in cold smoked salmon after treatment for 10, 20, 30 and 60 seconds. Effects on the total number of aerobic bacteria, lactic acid bacteria and Bacillus spores were also studied. Two experiments were performed, one in July 2005 and the other in November 2006. The study showed that short-term hypertension treatment was effective in improving the quality and safety of cold-smoked products. Due to changes in the appearance and texture of the products, further research is needed. This new method promises to meet the requirements for longer shelf life of smoked salmon. The study is of great value to the industry, due to the innovation of using high pressure for a short time (seconds) to eliminate the bacterium Listeria in smoked salmon and thus increase the shelf life of this valuable product.

The main object of this research was to study the effects of high pressure processing (400-900 MPa) on the survival of Listeria monocytogenes and the characteristics (microstructure, texture and color) of cold smoked salmon when it was processed for 10, 20, 30 and 60 seconds. The changes in counts of total aerobic bacteria, lactic acid bacteria and Bacillus spores were also studied. Two experiments were carried out, one in July 2005 and the second in November 2006. It is concluded here that the combination of high pressure and short time treatment is very effective to improve the quality and safety of cold smoked products. However, because of the changes in the visual appearance and texture, further studies are necessary. This new development is promising to meet requirements for extended shelf life of ready-to-eat cold smoked salmon with high microbiological quality and safety. This study is of high industrial relevance because it combines the innovative approach of using high pressure processing for short time (seconds) to reduce the number of Listeria in cold smoked salmon and thereby extend the shelf life of this valuable product.

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