Reports

Influence of seasonal variation and frozen storage temperature on the lipid stability of Atlantic mackerel (Scomber scombrus)

Published:

01/12/2016

Authors:

Paulina E. Romotowska, Magnea G. Karlsdóttir, María Gudjónsdóttir, Hörður G. Kristinsson, Sigurjón Arason

Supported by:

AVS Fisheries Research Fund (R 040-12)

Influence of seasonal variation and frozen storage temperature on the lipid stability of Atlantic mackerel (Scomber scombrus)

The effect of the storage temperature (-18 ° C vs. 25 ° C) and the fishing season (August vs. September) on the decomposition of fat in Atlantic mackerel caught off the coast of Iceland were examined in this project. Fat stability was assessed by measuring first-stage (PV) and second-degree evolution (TBARS), free fatty acids (FFA) and fatty acid composition. The results show a significant difference in fat degradation with long-term storage, as the degradation was significantly less when stored at -25 ° C compared to -18 ° C. In addition, fish were caught in September with a higher development value compared to fish from August. On the other hand, the most enzymatic fat breakdown was higher in August than in September. The results also indicated that the amount of omega-3 polyunsaturated fatty acids was fairly stable throughout the storage period. In other words, the results showed that the temperature in the cold store had a great effect on fat breakdown, but the stability depended on when the fish was caught.

Lipid deterioration of Atlantic mackerel (Scomber scombrus) caught in Icelandic waters was studied, as affected by different frozen storage temperatures (-18 ° C vs. -25 ° C) and seasonal variation (August vs. September). The lipid stability was investigated by analyzes of hydroperoxide value (PV), thiobarbituric acid reactive substances (TBARS), free fatty acids, as well as changes in fatty acid composition. Results showed significant lipid deterioration with extended storage time, where the lower storage temperature showed significantly more protective effects. Furthermore, a higher lipid oxidation level was recorded for fish caught in September than in August, although lipid hydrolysis occurred to be greater for fish in August than in September. Moreover, results indicated a rather stable level of omega-3 fatty acid during the entire frozen storage period. The analysis indicated that both lipid oxidation and hydrolysis were affected by the frozen storage temperature and the stability differed with regards to season of catch.

Report closed until 01.01.2018

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Reports

Impact of season, bleeding methods and storage temperature on the quality and stability of frozen cod climbs

Published:

01/04/2016

Authors:

Magnea G. Karlsdóttir, Sigurjón Arason, Ásbjörn Jónsson

Supported by:

AVS Fisheries Research Fund

contact

Sigurjón Arason

Chief Engineer

sigurjon.arason@matis.is

Impact of season, bleeding methods and storage temperature on the quality and stability of frozen cod climbs

The main goal of the project was to increase utilization and at the same time knowledge of the stability of cod climbing in frost according to the season. With increased knowledge of the effects of the season, the quality of raw materials and storage conditions on the stability of the liver in frost, it is possible to ensure that raw materials for further processing are available all year round. This report discusses the effects of the season, bleeding methods and storage temperature on the quality and stability of frozen cod climbs. Evaluation factors included enzymatic activity (free fatty acids) and evolution (primary and secondary subjects' evolution). Seasonality had a significant effect on the chemical composition and enzyme activity of the liver. This was reflected in higher fat content and higher levels of free fatty acids in the liver collected in July compared to liver from April. Frost stability also varied with the time of year as the liver from July was more susceptible to peroxide formation. Different bleeding methods (bleeding and gutting in one go (one step) and bleeding first and then gutting (two steps)) generally had little effect on the chemical composition and enzymatic activity of the liver. The haemorrhage methods, on the other hand, had a significant effect on the formation of a second-stage imagery of frostbite during storage, as the liver from fish bled in 2 steps was less craving compared to the liver from fish bled in one step. Storage temperature and time had a decisive effect on the stability of the livers in frost. Based on the available results, it is recommended to store frozen liver at -25 ° C rather than -18 ° C in order to slow down the damage process.

To our knowledge, there is limited information available regarding the effects of temperature, bleeding method, and seasonal variation on oxidation stability of cod liver during frozen storage. A profound knowledge of cod liver stability during frozen storage is needed to secure the available supply of cod liver for processing all year around. The objective of the present study was therefore to evaluate lipid deterioration during frozen storage of cod liver. The effects of temperature, storage time, bleeding method, and seasonal variation on lipid hydrolysis and oxidation were analyzed. Time of year significantly affected the chemical composition and enzymatic activity of the liver, which was reflected in a higher fat content and higher level of free fatty acids in the liver collected in July compared to liver collected in April. Stability during frozen storage also varied with season where liver from July was more vulnerable towards peroxidation. Different bleeding methods (bleeding and gutting in one step compared to bleeding first and then gutting (two steps)) had significant effect on the lipid oxidation where liver from fish bled in one step turned out to be more rancid compared to liver from fish bled in two steps. Storage temperature and time proved to be important factors with regard to lipid degradation of cod liver during frozen storage. Based on present results, in can be recommended to store frozen liver at - 25 ° C rather than -18 ° C in order to slow down these damage reactions.

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Reports

Effect of brining and frozen storage on physicochemical properties of well-fed Atlantic mackerel (Scomber scombrus) intended for hot smoking and canning

Published:

01/12/2015

Authors:

Paulina E. Romotowska, María Gudjónsdóttir, Magnea G. Karlsdóttir, Sigurjón Arason, Ásbjörn Jónsson, Hörður G. Kristinsson, Telma B. Kristinsdóttir

Supported by:

AVS Fisheries Research Fund (R 040-12)

contact

Sigurjón Arason

Chief Engineer

sigurjon.arason@matis.is

Effect of brining and frozen storage on physicochemical properties of well-fed Atlantic mackerel (Scomber scombrus) intended for hot smoking and canning

Mackerel (Scomber scombrus) is a relatively new species off the coast of Iceland. As mackerel is a fatty fish with a short shelf life, it therefore requires maximization of storage conditions and processing processes. In this project, changes in the chemical and physical properties of the heat treatment of salted and unsalted mackerel were studied. Prior to processing, the fish was stored for 6, 9 and 12 months at -18 ° C and -25 ° C with a view to examining how well Icelandic frozen mackerel is suitable as a raw material in canned and hot-smoked products. To examine the effect of heat treatment on the processing properties of mackerel, the samples were heated to 75 ° C (to simulate smoking) and 90 ° C (to simulate canning). Prolonged storage in the freezer had a negative effect on the raw material due to increased development and the fish stored at -18 ° C had a significantly poorer quality compared to fish stored at -25 ° C before processing. The results showed that a product heated to 75 ° C had a higher water content, higher water resistance and higher utilization and was also higher compared to a product heated to 90 ° C. Overall, the results indicate that a fat summer marker could be well suited for the processing of canned and hot-smoked products.

Atlantic Mackerel (Scomber scombrus) is a novel species in Iceland and as a fatty fish with a short shelf-life it requires optimization of storage and processing conditions. Physicochemical changes of brined and un-brined mackerel were analyzed during frozen storage (6, 9, 12 months) at -18 ° C vs. -25 ° C with the aim of investigating the suitability of using well-fed frozen mackerel as raw material for canned and hot-smoked products. Heat treatments to a core temperature of 90 ° C (representing canning) and 75 ° C (representing hot-smoking) were applied. Prolonged frozen storage showed negative effects on the raw material prior to heat processing due to an increased level of lipid oxidation, where fish stored at -18 ° C was of significantly poorer quality than fish stored at -25 ° C. Moreover, the results indicated that heat treatment resulting in a core temperature of 75 ° C showed higher water content, liquid holding capacity, heating yield as well as lower maximum shear force of texture compared to mackerel heated to a core temperature of 90 ° C. Overall, analyzes indicated that the fatty summer mackerel was well suited for the production of canned and hot-smoked products.

Report closed until 01.01.2018

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