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The effect of liquid cooling at processing and different cooling techniques during transport of cod (Gadus morhua) fillets

Author(s):

Hannes Magnússon, Lárus Þorvaldsson, Kolbrún Sveinsdóttir, Hélène L. Lauzon, Kristín Anna Þórarinsdóttir, 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 liquid cooling at processing and different cooling techniques during transport of cod (Gadus morhua) fillets

Tilgangur tilraunanna var að kanna áhrif mismunandi kælitækni og áhrif hitasveiflna á gæði og geymsluþol þorskflaka. Eftirfarandi kælitækni var könnuð: Vökvakæling í pækli við vinnslu miðað við enga kælingu og áhrif hitasveiflna við geymslu í samanburði við stöðugt hitastig (-1°C). Auk þess voru könnuð áhrif þess að nota annars vegar ísmottur og hins vegar þurrís við geymslu flakanna. Fylgst var með breytingum á hitastigi með hitanemum á öllum stigum. Sýni voru gæðametin með skynmati, örveru- og efnamælingum í allt að 14 daga frá veiði (11 daga frá vinnslu og pökkun). Mismunandi meðhöndlun leiddi til mismunandi ferskleikatíma og geymsluþols samkvæmt skynmati. Hópar sem voru vökvakældir við vinnslu höfðu um 2-3 daga skemmra geymsluþol en flök sem ekki voru kæld á þennan hátt. Rekja mátti ástæður þessa til þess að kælipækillinn innihélt töluvert magn örvera m.a. skemmdargerilinn Photobacterium phosphoreum sem er mjög virkur framleiðandi á trímetýlamíni (TMA). Samanburður á vökvakældu flökunum sýndi að notkun á þurrís lengdi geymsluþol um 1-2 daga í samanburði við ísmottur. Geymsla við -1°C hafði ekki merkjanleg áhrif á ferskleikatíma og geymsluþol í samanburði við flök þar sem hitasveiflum var beitt samkvæmt skynmati. Niðurstöður örveru- og efnamælinga voru í samræmi við þessar niðurstöður.

The aim of the experiment was to investigate the effects of different cooling techniques and temperature fluctuations on the storage life of cod fillets. The following cooling techniques were studied: liquid cooling in brine at plant as compared to no special cooling at processing. The effect of real temperature (RTS) simulation during storage was compared to a steady storage temperature at -1°C. Additionally, the influence of using either dry ice or ice packs during storage was studied. The temperature history of each group was studied using temperature loggings. The samples were analyzed with sensory evaluation, microbial and chemical methods for up to 14 days from catch (11 days from packaging). The different treatments of the groups resulted in different lengths of freshness period and maximum shelf life according to sensory evaluation. Liquid cooling resulted in a 2-3 days shorter maximum shelf life than the group that was not receiving liquid cooling. This could be attributed to the fact that the cooling brine carried considerable amounts of microbes including the spoilage bacterium Photobacterium phosphoreum which is an active producer of trimethylamine (TMA). Comparison of the groups receiving liquid cooling showed that dry ice appeared to extend the shelf life of 1-2 days as compared to ice packs. Storage at -1°C did not have much influence on the freshness period or maximum shelf life. These results were confirmed by total volatile bases (TVB-N) and TMA analysis and microbial counts.

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