Reports

Effects of temperature fluctuations during storage and transport on quality and stability of frozen mackerel products

Published:

01/12/2015

Authors:

Magnea G. Karlsdóttir, Paulina E. Romotowska, Sigurjón Arason, Ásbjörn Jónsson, Magnús V. Gíslason, Arnljótur B. Bergsson

Supported by:

AVS Fisheries Research Fund (R 040-12)

contact

Sigurjón Arason

Chief Engineer

sigurjon.arason@matis.is

Effects of temperature fluctuations during storage and transport on quality and stability of frozen mackerel products

The aim of the project "Maximizing the quality of frozen mackerel products" is to study the quality and stability of mackerel products in frost according to the seasons and the effects of different pre-cooling, freezing and storage conditions. By looking at the interplay of these factors, it is possible to maximize the quality and utilization of mackerel and therefore at the same time its value. This is the first report from the project and it deals with the effects of temperature fluctuations during storage and transport on the quality and stability of frozen mackerel products. Evaluation factors included release, enzyme activity and evolution. Containers were transported to Japan. Whole frozen raw materials provided in late July and early September were frozen and stored at -25 ° C for one month. During "transfer", the product was stored at -18 ° C ± 5 ° C for one month. The samples were measured before freezing, after the "transfer", and thereafter every 3 months in storage at -25 ° C. For comparison, samples were stored at a constant temperature (-25 ° C). In addition, whole frozen mackerel products were stored for up to 12 months at -18 ° C as well as -15 ° C to assess the effects of different storage conditions. There was a clear difference in the quality and stability of frozen mackerel products that were stored at low and stable temperatures compared to products that were subjected to heat stress, for example due to container transport. The results show that mackerel should not be stored above - 25 ° C.

The aim of the project “Quality optimization of frozen mackerel products” is to study the quality and stability of mackerel products during frozen storage as affected by season, different pre-cooling methods, freezing techniques and storage conditions. This is the first report from the project and describes the effects of temperature fluctuations during storage and transportations on quality and stability of frozen mackerel products. The main attributes investigated were eg gaping, enzymatic activity and rancidity. Container shipment were simulated. Whole mackerel caught late July and early September was frozen and stored at -25 ° C for one month. During “transportation”, the products were heat abused at -18 ° C ± 5 ° C for one month. Samples were analyzed after freezing, the transportation and with 3 months interval during subsequent storage at -25 ° C. For comparison, samples were stored at stable temperature (-25 ° C). Additionally, frozen mackerel products were stored for up to 12 months at -18 ° C and -15 ° C to further evaluate the effects of storage temperature. A significant difference in quality and stability were detected between products stored at stable and low temperature and products that underwent heat abuse during eg transportation. The results demonstrate that frozen mackerel products should not be stored at higher temperatures than -25 ° C.

Report closed until 01.01.2018

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Reports

Effects of subcooling on salt uptake by pickling cod neck pieces (Gadus morhua)

Published:

01/06/2008

Authors:

Ragnhildur Einarsdóttir, María Guðjónsdóttir, Sigurjón Arason

Supported by:

Rannís Research Fund

contact

Sigurjón Arason

Chief Engineer

sigurjon.arason@matis.is

Effects of subcooling on salt uptake by pickling cod neck pieces (Gadus morhua)

Salt uptake and shelf life of skinless and boneless cod fillets (Gadus morhua) were studied at different temperatures. Salt uptake was examined at 0.5 ° C, -2 ° C and 5 ° C. The results indicate that fish muscle absorbs salt faster at -2 ° C than 5 ° C and salt uptake occurs most rapidly in the first 5 minutes. When looking for a final salt concentration of 0.6%, 4% brine is most desirable. In the shelf life test, the temperature was 0 ° C on the one hand and - 2 ° C on the other. Shelf life of fillets stored at -2 ° C was found to have a shelf life of 3-4 days longer than those stored at 0 ° C. Enzyme activity, more specifically trypsin-like protease activity, was examined in supercooled fish muscles. Fish muscle with a salinity of 0.5% stored at -2 ° C was found to have higher activity than other groups. The study suggests that it would be interesting to look more closely at the interaction between treatment, temperature and enzymes.

The salt uptake during brining and shelf life of skinless and boneless cod loins (Gadus morhua) was investigated at different temperatures. The salt uptake was studied at 0.5 ° C, -2 ° C and 5 ° C. The results show that the salt uptake of the cod muscle is faster at -2 ° C than at 5 ° C and that the salt uptake is fastest during the first 5 minutes. When aiming for a salt concentration of 0.6% in the muscle during brining it is optimal to use a 4% salt brine. In the shelf life study, samples were stored at 0 ° C and -2 ° C. The cod loins stored at -2 ° C showed 3-4 days longer shelf life than samples stored at 0 ° C. Enzymatic activity, or trypsin like protease activity to be more precise was studied in the superchilled muscle. Cod muscle with 0.5% salt and stored at -2 ° C showed higher activity than other groups. The study shows that there is a need for further studies on the combined effects of processing and storage temperatures on enzymatic activity.

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