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Effect of superchilled processing of whole whitefish – pre‐rigor / Áhrif ofurkælingar á skemmdarferla og geymsluþol heils fisks og flaka

Author(s):

Aðalheiður Ólafsdóttir, Björn Margeirsson, Kolbrún Sveinsdóttir, Sigurjón Arason, Eyjólfur Reynisson, Emilía Martinsdóttir

Funded by:

AVS Fund of Ministry of Fisheries in Iceland (R 062‐11)

Contact

Aðalheiður Ólafsdóttir

Sensory Evaluation Manager

adalheiduro@matis.is

Effect of superchilled processing of whole whitefish – pre‐rigor / Áhrif ofurkælingar á skemmdarferla og geymsluþol heils fisks og flaka

Markmið tilraunarinnar var að rannsaka áhrif ofurkælingar á skemmdarferla og geymsluþol heils fisks og flaka. Rannsókn var gerð á heilum þorski ofurkældum fljótlega eftir veiði og einnig á áhrifum ofurkælingar á flök unnum úr ofurkældum þorski og þorski kældum í ís á hefðbundinn hátt. Notaðar voru hitamælingar, skynmat, efna‐  og örverumælingar til að bera eftirfarandi tilraunahópa saman, en þeir voru geymdir við –1.4 til –1.2 °C meðalhita:

1) NC: heill þorskur kældur í ís

2) SC: ofurkældur heill þorskur

3) NC‐NC: hefðbundin flakavinnsla úr heilum þorski kældum í ís

4) NC‐SC: ofurkæld flök unnin úr heilum þorski kældum í ís

5) SC‐NC: hefðbundin flakavinnsla úr ofurkældum heilum þorski

6) SC‐SC: ofurkæld flök unnin úr ofurkældum heilum þorski

Niðurstöður skynmats benda til þess að ofurkæld vinnsla á heilum þorski geti lengt geymsluþol hans um tvo daga. Ofurkæling á heilum þorski hafði ekki áhrif á sýrustig, vatnsinnihald, vatnsheldni og örveruvöxt í heilum fisk samanborið við fisk sem ekki var ofurkældur í vinnslu. Samkvæmt skynmati var lítinn mun að finna á geymsluþoli mismunandi flakahópa. Geymsluþol var metið 16–18 dagar, sem er nokkuð langur tími fyrir þorskflök. Ferskleikatímabil tilraunahópsins SC‐ SC virtist þó vera heldur lengra en hinna hópanna. Líkt og fyrir heila þorskinn reyndist lítill munur milli flakahópanna m.t.t. örveruvaxtar, efna‐ og eðliseiginleika. Takmarkaðan mun milli tilraunahópa má mögulega skýra með stöðugum og ofurkældum geymsluaðstæðum. Með hliðsjón af því er ráðgert að framkvæma aðra sambærilega tilraun þar sem hermt verður eftir dæmigerðari umhverfishitaferlum í flutningi ferskfiskafurða (0–4 °C) en í þessari tilraun (–1.4 til –1.2 °C).

The main aim of the study was to study the effects of superchilled processing on storage life of both whole fish and fillets. The following experimental groups were evaluated by means of temperature monitoring, chemical‐ and microbial measurements and sensory evaluation, which were stored at mean temperatures of –1.4 to –1.2 °C:

1) NC: non‐superchilled whole cod

2) SC: superchilled whole cod

3) NC‐NC: non‐superchilled fillets from non‐superchilled whole cod

4) NC‐SC: superchilled fillets from non‐superchilled whole cod

5) SC‐NC: non‐superchilled fillets from superchilled whole cod

6) SC‐SC: superchilled fillets from superchilled whole cod

The results from the sensory evaluation indicate that superchilled processing of whole cod can extend shelf life by two days. Differences in values of pH, water content, water holding capacity and bacterial growth between the superchilled and non‐superchilled whole fish groups were minor. Differences in sensory scores between the fillet groups were small. Shelf life was estimated between 16 and 18 days which is quite long shelf life for cod fillets. However, the group SC‐SC seemed to retain freshness a little longer than other groups. As in case of the whole cod, the differences in bacterial count, chemical and physical properties between the fillet groups were small. Very similar fish temperatures between both the whole fish and the fillets groups resulting from the superchilled storage conditions applied may be the main reason for the small differences obtained. Thus, another study with more common temperature conditions during transport and storage of fresh fish (chilled but not superchilled) will be performed.  

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Categories
Reports

The effect of different cooling techniques on the quality changes and shelf life of whole cod (Gadus morhua)

Author(s):

Hannes Magnússon, Kolbrún Sveinsdóttir, Lárus Þorvaldsson, María Guðjónsdóttir, Hélène L. Lauzon, Eyjólfur Reynisson, Árni R. Rúnarsson, Sveinn H. Magnússon, Jónas R. Viðarsson, Sigurjón Arason, Emilía Martinsdóttir

Funded by:

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

Contact

Kolbrún Sveinsdóttir

Project Manager

kolbrun.sveinsdottir@matis.is

The effect of different cooling techniques on the quality changes and shelf life of whole cod (Gadus morhua)

Tilgangur tilraunarinnar var að kanna áhrif þriggja mismunandi kæliaðferða á geymsluþol heils, slægðs þorsks: (i) Kæling með muldum plötuís, (ii) kæling með vökvaís, (iii) forkæling með vökvaís og síðan kæling með muldum plötuís. Fylgst var með hitastigsferlum með hitanemum í öllum hópum yfir geymslutímann. Sýni voru metin með skynmats-, örveru- og efnamælingum þá 10 daga sem fiskurinn var í geymslu. Niðurstöður örveru- og efnamælinga voru yfirleitt í góðu samræmi við niðurstöður skynmats. Samanburður á tilraunahópum leiddi í ljós að þorskur kældur með vökvaís hafði um tveggja til þriggja daga skemmra geymsluþol en hinir tveir hóparnir. Geymsluþol þorsksins var töluvert styttra en ýmsar fyrri rannsóknir hafa sýnt og þá sérstaklega í hópnum sem var kældur með vökvaís (aðeins 9-10 dagar). Nú liggur fyrir að þorskurinn sem var kældur með vökvaís var vanísaður um borð í veiðiskipinu miðað við hina tvo hópana. Auk þess var kæling við geymslu eftir löndun ekki eins góð og æskileg gæti talist en hitastigið sveiflaðist á milli 2-5 °C. Þetta gæti mögulega skýrt skemmra geymsluþol allra hópa miðað við fyrri rannsóknir.

The aim of this experiment was to investigate the effect of three different cooling methods on the storage quality of whole, bled gutted cod: (i) Cooled with crushed plate ice, (ii) cooled with liquid ice, (iii) pre-cooled in liquid ice and then cooled with crushed plate ice. The temperature history of each group was studied using temperature loggers. The samples were analysed with sensory, microbiological and chemical methods for up to 10 days from catch. The results from microbial and chemical measurements were generally in good agreement with the results from sensory evaluation. Comparison of the groups showed that the use of liquid ice instead of plate ice resulted in two to three day shorter shelf life than in the other two groups. The shelf life in this study was considerably shorter compared to previous studies with whole cod, especially in the experimental group where liquid ice was used for cooling (only 9-10 days). It is now known that the liquid iced group in this experiment was insufficiently iced on board the fishing vessel compared to the other two groups. Additionally, the ambient temperature in the cold room of the fish plant was relatively high and fluctuated between 2 – 5 °C during the storage period. This could possibly explain the shorter shelf life of all groups compared to some earlier studies.

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