7 Genomic Approaches in Aquaculture and Fisheries
235
These results suggest that the transcription profile at cellular level can be a sensitive
indicator of freshness during on-ice storage.
Other studies involving proteome analysis have assessed post-mortem changes in
seafood (Kjærsgård and Jessen 2003, Martinez and Friis 2004, Morzel et al. 2000,
Verrez-Bagnis et al. 2001, Schiavone et al. 2008), demonstrating the complexity of
proteolysis in seafood during storage and processing. To assess post mortem muscle integrity, the effect of two different pre-slaughter procedures (limited or 15 min
intense muscular activity) on muscle trout proteins was investigated through a proteome analysis (Morzel et al. 2006). Persistent under-representation of desmin, a
key cytoskeletal protein, in fish submitted to intense muscular activity suggests that
such a pre-slaughter treatment can affect the composition of post-mortem muscle
integrity.
Frozen storage is an excellent option to increase the shelf life of fish and meat
products but prolonged storage, high frozen storage temperatures, or fluctuating
temperatures have a negative effect on product quality such as development of rancid taste and odor in fatty fish (Min and Ahn 2005). Frozen storage also leads to a
decrease in protein solubility (Saeed and Howell 2002) and changes in texture quality, such as increased toughness and loss of juiciness (Mackie 1993). Recent studies
in rainbow trout and cod identified proteome changes associated to degradation
and oxidation processes during frozen storage (Kjærsgård et al. 2006a, b) concluding that both structural (MHC, actin and tropomyosin) and cytoplasmic (creatine
kinase and enolase) proteins were being heavily oxidized. On the contrary, nucleoside diphosphate kinase (NDPK) appeared to be only weakly carbonylated, but its
solubility was dependent on the frozen storage temperature, opening the possibility
for its usage as a biomarker of frozen storage conditions.
The increasing scientific output over recent years in this area indicates that
genomics, proteomics and transcriptomics, with their capacity to monitor multiple
biochemical processes simultaneously, are methodologies eminently suitable to find
biochemical/metabolic markers useful for predicting/monitoring features such as
flesh texture of fish farmed under different environmental conditions and subjected
to various ante- and post-mortem practices.
7.5.2.4 Nutritional Quality and Health Value
The nutritional quality and health value of fish is mostly associated with its fat content and fatty acid profile in the muscle. Fish are the only major dietary source for
humans of n-3 highly unsaturated fatty acids (HUFA) and with the decline of wild
stocks, the proportion of farmed fish is increasing in the human diet. The use of high
energy diets in farmed fish (e.g. trout, salmon) can increase energy storage in viscera, liver and to a lesser extent in muscle, with the consequence of excess adiposity,
generally not desirable in aquaculture products. In general terms, farmed fish tend
to have higher levels of whole body lipids than their wild counterparts. The fatty
acid composition of fillets from farmed fish is strongly influenced by the feed lipid
composition. The relative n-3 HUFA content of farmed fish tends to be lower than
that of wild-caught fish, but the amount provided per portion is likely to be similar,
235
These results suggest that the transcription profile at cellular level can be a sensitive
indicator of freshness during on-ice storage.
Other studies involving proteome analysis have assessed post-mortem changes in
seafood (Kjærsgård and Jessen 2003, Martinez and Friis 2004, Morzel et al. 2000,
Verrez-Bagnis et al. 2001, Schiavone et al. 2008), demonstrating the complexity of
proteolysis in seafood during storage and processing. To assess post mortem muscle integrity, the effect of two different pre-slaughter procedures (limited or 15 min
intense muscular activity) on muscle trout proteins was investigated through a proteome analysis (Morzel et al. 2006). Persistent under-representation of desmin, a
key cytoskeletal protein, in fish submitted to intense muscular activity suggests that
such a pre-slaughter treatment can affect the composition of post-mortem muscle
integrity.
Frozen storage is an excellent option to increase the shelf life of fish and meat
products but prolonged storage, high frozen storage temperatures, or fluctuating
temperatures have a negative effect on product quality such as development of rancid taste and odor in fatty fish (Min and Ahn 2005). Frozen storage also leads to a
decrease in protein solubility (Saeed and Howell 2002) and changes in texture quality, such as increased toughness and loss of juiciness (Mackie 1993). Recent studies
in rainbow trout and cod identified proteome changes associated to degradation
and oxidation processes during frozen storage (Kjærsgård et al. 2006a, b) concluding that both structural (MHC, actin and tropomyosin) and cytoplasmic (creatine
kinase and enolase) proteins were being heavily oxidized. On the contrary, nucleoside diphosphate kinase (NDPK) appeared to be only weakly carbonylated, but its
solubility was dependent on the frozen storage temperature, opening the possibility
for its usage as a biomarker of frozen storage conditions.
The increasing scientific output over recent years in this area indicates that
genomics, proteomics and transcriptomics, with their capacity to monitor multiple
biochemical processes simultaneously, are methodologies eminently suitable to find
biochemical/metabolic markers useful for predicting/monitoring features such as
flesh texture of fish farmed under different environmental conditions and subjected
to various ante- and post-mortem practices.
7.5.2.4 Nutritional Quality and Health Value
The nutritional quality and health value of fish is mostly associated with its fat content and fatty acid profile in the muscle. Fish are the only major dietary source for
humans of n-3 highly unsaturated fatty acids (HUFA) and with the decline of wild
stocks, the proportion of farmed fish is increasing in the human diet. The use of high
energy diets in farmed fish (e.g. trout, salmon) can increase energy storage in viscera, liver and to a lesser extent in muscle, with the consequence of excess adiposity,
generally not desirable in aquaculture products. In general terms, farmed fish tend
to have higher levels of whole body lipids than their wild counterparts. The fatty
acid composition of fillets from farmed fish is strongly influenced by the feed lipid
composition. The relative n-3 HUFA content of farmed fish tends to be lower than
that of wild-caught fish, but the amount provided per portion is likely to be similar,