Year of grant:

Research Area:
Náttúra og náttúrutilfeingi

Project type:

Project title:
Proteoglycans (PGs), glycosaminoglycans (GAGs) and collagen in the connective tissue of fish muscle.

Grant number:

Project manager:
Ása Jacobsen


Project period:
01.01.2011 - 01.07.2014

Total budget:
2,093,752 DKK

Grant from the FRC in DKK:
600.000 DKK

Project description:
Growing awareness related to the quality of fish fillets, including soft texture and holes in the surface (gaping), has led to financial losses to the fish and fish farming industry. It is relatively well documented that the rapid softening that follows the end of rigor mortis and gaping is to some degree related to its collagen content and the action of specific collagenase enzymes on the collagen helices contributing to an increase in its solubility. However, relating these quality problems of fish fillets to only a specific protein has proved to be too simplified. Even if many universities worldwide have invested a lot of time and money in research concerning the relationship between collagen and the quality of fish fillets, only limited effort has been made to include the effect of PGs and GAGs, which interact with collagen in the extracellular matrix (ECM) of the connective tissue in fish muscle. The primary objective of the present Ph.D. study is to investigate the content and composition of PGs and GAGs as well as the content and degradation of collagen in the connective tissue in order to determine how the interaction between PGs, GAGs and collagen in the connective tissue influence gaping and the loss of firmness of fish fillets. The goal is to produce scientific data concerning the content and degradation of the macromolecules in the connective tissue of fish muscle as well as methods that could counteract the deterioration process.

Gaping in salmon fillets is a major quality issue in the salmon farming industry. This project investigated potential causes of gaping by examining effects of various processes in slaughter and storage. An experimental setup examined the effects of cleaning intensity of the abdominal cavity of slaughtered salmon prior to cold storage. The results from the quality assesment performed after the salmon had been in cold storage for a week showed that blood and other bodily fluids left in the abdominal cavity during storage induced gaping. The gaping severity was significantly higher in those salmon not cleaned properly. Tissue samples taken from these salmon were analysed by extracting glycosaminoglycans and examining these by mass spectrometry. Glycosaminoglycans are important components of the connective tissue, which in gaping fillets loses its connection to the adjecent muscle sheets causing gaping in the fillets. The results showed that there were differences in the structure and content of the glycosaminoglycans in intact and gaping tissue. Some of these differences were potentially caused by enzymatic activity of bacteria although other explanations for the differences detected are also possible. An experimental setup examining the composition of the bacterial communities present in the intestines of salmon at slaughter and in the skin mucus, abdominal cavity and storage ice during the subsequent storage showed that at some occasions the bacterial community in the abdominal cavity during storage was very similar to that found in the intestines at slaughter. This indicates that in some occasions intestinal fluids is transferred to the abdominal cavity during slaughter and is not removed entirely during the cleaning process. The enzymatic activity potentially degrading connective tissue components was high in the intestinal samples and those abdominal samples with similar bacterial composition. Contrary to this the enzymatic actvity was low in the other samples with different bacterial compositions. This suggested that there is a possible link between intestinal bacteria left in the abdominal cavity during storage and gaping in the salmon fillets. This has to be further examined and there are also other potential explanations.

Project status:

Project output:

Jacobsen Á, Joensen H, Eysturskarð J. (2017). Gaping and loss of fillet firmness in farmed salmon (Salmo salar L.) closely correlated with post-slaughter cleaning of the abdominal cavity. Aquaculture Research 48: 321-331.

Jacobsen Á, Shi X, Shao C, Eysturskarð J, Mikalsen S-O, Zaia J (2019). Characterization of glycosaminoglycans in gaping and intact connective tissue of farmed Atlantic salmon (Salmo salar L.) fillets by mass spectrometry. ACS Omega 4, 15337-15247.

Jacobsen Á, Mikalsen S-O, Joensen H, Eysturskarð J (2019). Composition and dynamics of the bacterial communities present in the post-slaughter environment of farmed Atlantic salmon (Salmo salar L.) and correlations to gelatin degrading activity. PeerJ 7:e7040.

Jacobsen Á, Eysturskarð J, Mikalsen S-O. Initial metagenomic screening of microbiome communities in stomach and intestines of four fish species inhabiting coastal waters. In prep

Jacobsen Á, Mikalsen S-O, Salter I. Comparison of custom made QIIME and standard pipeline SILVAngs bioinformatics for investigation of microbial communities in farmed salmon (Salmo salar L.) post-slaughter. In prep

Ása Jacobsen (2020). Exploring potential causes of gaping in salmon (Salmo salar L.) fillets. PhD thesis. NVD Rit 2020:07.

Ritgerðin varð vard 14. august 2020.


Aliráðstevnan, februar 2013: Gaping – veikur bindivevnaður

Framløgudagur hjá Fiskivinnugransking, februar 2015: Gaping – veikur bindivevnaður

Aliráðstevnan, mars 2017: Ávirkan á góðskuna hjá laksi

Visindavøkan, oktobur 2017: Sekvensering av bakteriusamfeløgum

Gransking í Føroyum, novembur 2017: Heildarmynd av bakteriusamfeløgum – tøknin, úrslit og møguleikar.

Aliráðstevnan, mars 2018: Bakteriusamfeløg á køligoymslu.

Granskingardagur, mai 2019: Gaping í laksaflaki lýst við biotøkni.

WEFTA, oktobur 2019: Gaping in salmon fillets – a different approach.

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