Reports

Effects of bleeding methods on the quality and storage life of cod and saithe products

Published:

01/02/2014

Authors:

Magnea G. Karlsdóttir, Nguyen Van Minh, Sigurjón Arason, Aðalheiður Ólafsdóttir, Paulina E. Romotowska, Arnjótur B. Bergsson, Stefán Björnsson

Supported by:

AVS (R 11 087‐11)

contact

Sigurjón Arason

Chief Engineer

sigurjon.arason@matis.is

Effects of bleeding methods on the quality and storage life of cod and saithe products

The aim of the project was to examine the effect of different bleeding methods on the quality and shelf life of different cod and saithe products. By identifying ideal conditions for bleeding, gutting and bleeding, it is possible to prevent product defects due to blood and at the same time increase the stability of the products in transport and storage. The fish were either bloodied in the hands and in the machine. Bleeding took place in slush or sea and the effects of different bleeding times were examined. The effect of waiting time on tires before bleeding was also assessed, as well as bleeding and gutting the fish in one step or two steps (gutting performed after bleeding). The products studied in this project were chilled and frozen cod and saithe products, as well as salted cod products. Of the variables studied in this project, their importance differed in terms of which fish species were involved and what the final product was. When comparing comparable sample groups of cod and saithe, it is seen that different conditions are suitable for each species. This supports the theory that it is probably not possible to transfer the best bleeding method of cod to saithe and vice versa. Bleeding time and type of bleeding agent (sludge vs. seawater) had a decisive effect on the stability of the cod and saithe products examined. Cod products, both chilled and frozen, from raw material soaked in sludge generally resulted in improved quality and stability compared to if soaked in seawater. In contrast to cod, the bleeding of saithe into the sea generally resulted in a stable end product. The way the fish were bled and gutted also had a decisive effect on the final products. In the case of frozen cod products, raw and gutted raw material in one step generally yielded a more stable product compared to raw material that was gutted after bleeding had occurred (two steps). Salted products, on the other hand, were much more stable in storage if the raw material was gutted after bleeding. Different results were also obtained for saithe depending on the final product involved. Bleeding and gutting of saithe in a machine had a positive effect on the shelf life of chilled products compared to if made by hand. Machine bleeding and gutting, on the other hand, resulted in a much more unstable product in the cold. The results of the project show that the effects of different bleeding methods are quite dependent on the raw material as well as the final product involved.

The main objective of the project was to study the effects of different bleeding methods on quality and storage life of various cod and saithe products. Products defects due to blood residues can be prevented by optimizing bleeding protocols, and hence increase the quality and storage life of the products. For this, fishes were either bled and gutted by hand or by machine. The bleeding (blood draining) was carried out with seawater or slurry ice, and the effects of different bleeding times in the tanks were also investigated. Moreover, the effects of waiting time (on deck) before bleeding, as well as the procedure of bleeding technique (bleeding and gutting in one procedure vs. gutting after blood draining) were investigated. The various products evaluated were chilled and frozen cod and saithe products, and salted cod products. The importance of the different parameters investigated in this project varied considerably with regard to fish species and the final products. Comparison of parallel treatments groups of cod and saithe demonstrated that optimum bleeding procedures are different for each species. Waiting time on deck and bleeding media (slurry ice vs. seawater) significantly affected the storage life of the cod and saithe products. Cod products, both chilled and frozen, from fish bled in slurry ice generally resulted in improved quality and storage life compared to fish bled in seawater. In contrast to cod, bleeding or saithe in seawater resulted however in more stable products. The procedure during bleeding and gutting also had great impact on the storage life of the various products studied. Shorter storage life of salted cod products was generally observed when the raw material was bled and gutted in one step compared to when gutting was performed after bleeding (two steps). Rather conflicting results were, however, observed for saithe and were depending on the type of final product. Bleeding and gutting of saithe by machine improved the storage life of chilled products compared to when the saithe was bled and gutted by hand. The machine procedure had, however, negative effects on the storage life of the frozen saithe products. Overall, the results of this project indicate that the effects of different bleeding methods are highly relative to fish species as well as the final product of interest.

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Reports

Shelf life tests on cod pieces: Effects of supercooling, pickling and gas packaging on the physical and chemical properties of cod muscles

Published:

01/12/2007

Authors:

María Guðjónsdóttir, Hannes Magnússon, Sigurjón Arason, Guðrún Ólafsdóttir, Sigurður Bogason

Supported by:

AVS, Rannís Technology Development Fund, Rannís Research Fund

contact

Sigurjón Arason

Chief Engineer

sigurjon.arason@matis.is

Shelf life tests on cod pieces: Effects of supercooling, pickling and gas packaging on the physical and chemical properties of cod muscles

An integrated refrigeration study was carried out on the effect of salting, different packaging methods and salting methods as well as the effect of subcooling on the quality and shelf life of cod muscles. The results show that storage is a more desirable salting method than injection salting from a microbiological point of view and with regard to drip and boiling efficiency. However, if the salinity during storage becomes too high, the muscle will gel. In the experiment, it was not considered to improve the quality of the fish to inject proteins into the muscle in addition to the salt. Microbial growth and the amount of wandering alkali decrease with decreasing temperature, so it is desirable to keep the temperature as low as possible, without the fish freezing. At -4 ° C, the surface of the fish in all groups, regardless of salinity, was frozen and the ice crystal formation increased with storage time. This ice crystal formation took place much more slowly at -2 ° C and is therefore considered a desirable storage temperature for lightly salted cod muscles. Air-packed packaging (MAP) also proved to be a more desirable storage method than foam packaging, as microbial growth and increase in erratic base was slower in the MAP packaging, which led to longer shelf life.

A combined cooling experiment was performed upon the effect of salting, different packaging and salting methods as well as the effect of superchilling on the quality and shelf life of cod muscle. The results show that brining is a better salting method that brine injection in terms of bacterial growth as well as increased yield. On the other hand, if the salt concentration becomes too high, gelation of the muscle proteins begins. The study also showed that injection of proteins along with salt injection did not improve the quality of the muscle. Microflora and the formation of volatile nitrogen bases decreased with lowering temperatures. It is therefore preferred to store fish at as low temperatures as possible, without letting the muscle water freeze. At -4 ° C the water at the muscle surface was frozen in all groups, independent of salt content, and the ice crystallization increased with storage time. This crystallization was much slower at -2 ° C and therefore this temperature is recommended for storage of light salted cod muscle. Modified Atmosphere Packaging (MAP) turned out to be a better packaging method than Styrofoam packaging, since the increase in bacterial growth and volatile nitrogen bases was slower in the MAP. This also lead to increased shelf life.

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Reports

Process control for fishing, processing and processing of salted fish. Effect of cooling after fishing on the muscular structure of cod

Published:

01/08/2007

Authors:

Valur N. Gunnlaugsson, Jónína Ragnarsdóttir, Þóra Valsdóttir, Kristín Anna Þórarinsdóttir

Supported by:

AVS, Rannís Technology Development Fund

contact

Valur Norðri Gunnlaugsson

Group Leader

valur.n.gunnlaugsson@matis.is

Process control for fishing, processing and processing of salted fish. Effect of cooling after fishing on the muscular structure of cod

This report describes the results of a cod image analysis. The effect of cooling methods after fishing on the muscular cod stock was assessed. It was not possible to detect differences in fillets depending on whether the fish had been stored in liquid ice or flake ice in a train or had been cooled separately on deck. Muscle changes during salt fish processing were monitored and the effect of injection was assessed. During salting, cells contracted and the extracellular space increased. There was a clear difference in the fillets depending on whether they were injected or not. During dehydration, the difference due to injection decreased again.

Results from image analyzes on cod are discussed in this report. The effects of chilling methods after catch on microstructure of cod fillets were also evaluated. No significant effects were observed, neither when extra chilling was added on deck nor with regard to different ice types (liquid ice / flake) used for storage of the fish. Changes in the fish muscle during heavy salting were examined and the effects of injection as the initial step in the process studied. During salting muscle cells shrank and the ratio of extracellular fluid increased. Significant effects of injection were observed after salting but during rehydration the difference decreased again.

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