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

Author(s):

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

Funded by:

AVS rannsóknasjóður í sjávarútvegi (R 040-12)

Contact

Hörður G. Kristinsson

Rannsókna- og nýsköpunarstjóri

hordur.g.kristinsson@matis.is

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

Áhrif geymsluhitastigs (-18 °C vs. 25 °C) og veiðitíma (ágúst vs. september) á niðurbrot fitu í Atlantshafs makríl veiddum við Íslandsstrendur voru skoðuð í þessu verkefni. Stöðugleiki fitunnar var metinn með því að mæla fyrstastigs (PV) og annarsstigs myndefni þránunar (TBARS), fríar fitusýrur (FFA) auk fitusýrusamsetningu. Niðurstöðurnar sýna marktækan mun í fituniðurbroti með langvarandi geymslu, þar sem niðurbrotið var marktækt minna þegar geymt var við – 25 °C samanborið við -18 °C. Auk þessa var fiskur veiddur í september með hærri þránunargildi samanborið við fisk frá ágúst. Aftur á móti var ensímatískst fituniðurbrot meira í águst en september. Niðurstöðurnar gáfu einnig til kynna að magn ómega-3 fjölómettaðra fitusýra var nokkuð stöðugt út geymslutímann. Með öðrum orðum þá sýndu niðurstöðurnar að hitastig í frostgeymslu hafði mikil áhrif á fituniðurbrot en stöðugleikinn var háður því hvenær fiskurinn var veiddur.

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 analyses 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 whole 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.

Skýrsla lokuð til 01.01.2018

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Categories
Reports

Seasonal and geographical variation in chemical composition and lipid stability of Atlantic mackerel (Scomber scombrus) caught in Icelandic waters

Author(s):

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

Funded by:

AVS rannsóknasjóður í sjávarútvegi (R 040-12)

Contact

Sigurjón Arason

Head Engineer

sigurjon.arason@matis.is

Seasonal and geographical variation in chemical composition and lipid stability of Atlantic mackerel (Scomber scombrus) caught in Icelandic waters

Á þeim tíma sem makríll er við íslandsstrendur er hann í miklu æti sem veldur því að hann snögg fitnar með þeim afleiðingum að holdið verður mjög viðkvæmt fyrir meðhöndlun. Í þessari rannsókn var makríll sem var veiddur sumarvertíðarnar 2012 og 2013 (júlí, ágúst, september) og frá mismunandi veiðisvæðum (austur, norðaustur, suður og suðaustur) skoðaður. Til þess að meta á hversu vel hráefnið hentar til vinnslu á hágæðaafurðum til manneldis, var makríllinn mældur m.t.t. vatns- og fituinnihalds, fitusýrusamsetningar, litar, þránunar og frírra fitusýra. Almennt var makríllinn sem safnað var sumarið 2012 af betri gæðum en makríll frá 2013. Niðurstöðurnar gáfu einnig til kynna breytileika á milli veiðimánaða m.t.t. fituinnihalds og framgang þránunar. Makríll sem var veiddur um miðbik vertíðarinnar hafði lægsta þránunargildið, sem gefur til kynna að sá makríll hentar best fyrir vinnslu á hágæðaafurðum til manneldis.

Atlantic mackerel (Scomber scombrus) appears in Icelandic waters during its heavy feeding period, resulting in variation in mackerel products quality. Fish caught at different season during the summers of 2012 and 2013 (July, August, September) and at different sites of the Icelandic fishing area (East, Northeast, South and Southeast) were analysed. Measurements of lipid and water content, fatty acid composition, colour changes, lipid hydroperoxide (PV), thiobarbituric reactive substances (TBARS) and free fatty acid (FFA) were studied with the aim of investigating whether this raw material was suitable for the production of high quality products for human consumption. In general, samples collected during the summer of 2012 showed a better condition than fish from 2013. The results indicated seasonal variation in lipid content and rancidity development. The lowest rancidity values were observed in the middle of the Icelandic catching season, indicating that this raw material was best suited for production of high quality products. Moreover, geographical variation of the mackerel catches had an impact on the saturation of the fatty acids, and appeared as follows: East > Southeast > Northeast > South.

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Breytileiki í fituinnihaldi og eiginleikum þorsks eftir árstíma / Seasonal variation of fatty acid composition of cod flesh

Author(s):

Kristín Anna Þórarinsdóttir, Helga Gunnlaugsdóttir, Jónas R. Viðarsson, Sigurjón Arason

Funded by:

Verkefnasjóður Sjávarútvegsins

Contact

Helga Gunnlaugsdóttir

Group Leader

helga@matis.is

Breytileiki í fituinnihaldi og eiginleikum þorsks eftir árstíma / Seasonal variation of fatty acid composition of cod flesh

Í skýrslunni eru teknar saman niðurstöður mælinga á efnainnihaldi lifrar og þorskvöðva eftir árstíma og veiðislóð. Niðurstöður benda til þess að árstíðabundnar sveiflur í fituinnihaldi vöðva séu tiltölulega litlar. Öðru máli gegnir um lifur, fituinnihald hennar reyndist lægst síðari hluta vetrar og að vori. Á sama tíma var vatnsinnihald hæst.   Breytingar í efnasamsetningu lifrar voru taldar tengjast þeim sveiflum sem verða í hegðunarmynstri og líkamsstarfsemi fisksins í kringum hrygningu.

The report summarizes the results from measurements on chemical composition of liver and muscle of cod as affected by fishing grounds and seasonal variation. The results indicate that seasonal fluctuations in fat content of the muscle are relatively low. On the contrary, fat and water content in liver, varied with season. The fat content was lowest   late winter and in spring. At the same time, the highest water content in liver was observed.   These changes were explained by changes in behaviour and physiological functional of the fish in relation to the reproductive cycle.

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Reports

Production of salted fish in the Nordic countries. Variation in quality and characteristics of the salted products

Author(s):

Kristín Anna Þórarinsdóttir, Ingebrigt Bjørkevoll, Sigurjón Arason

Funded by:

NORA (Journal nr. 510‐036)

Contact

Sigurjón Arason

Head Engineer

sigurjon.arason@matis.is

Production of salted fish in the Nordic countries.   Variation in quality and characteristics of the salted products

The Nordic countries are the largest exporters of salted gadoid products, whereas countries in South‐Europe and Latin America are the biggest importers. In Norway, Iceland and Faroe Islands, cod is primarily used for the production. The characteristics of the salted fish, such as commercial quality and weight yield vary between the countries and between producers. These attributes are influenced by differences in catching methods, handling and salting methods. This report summarises the variation in these procedures, and in addition, the market segmentation of salted products, from the different countries.

Meginhluti saltfiskframleiðslu í heiminum fer fram innan norrænu landanna en stærsti neytendahópurinn er í S‐Evrópu og S‐Ameríku.   Þorskur er megin hráefnið en einnig er framleiddur saltfiskur úr öðrum skyldum tegundum, s.s. ufsa, löngu, ýsu og keilu.    Eiginleikar saltfiskafurð, svo sem gæði og nýting, eru breytilegir milli framleiðslulanda og framleiðenda.    Þessir breytur eru háðar veiðiaðferðum, hráefnismeðhöndlun og söltunaraðferðum.    Skýrslan er samantekt á breytileika í þessum þáttum milli framleiðslulanda, ásamt úttekt á hlutdeild þeirra á saltfiskmörkuðum.

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