Minimization of Lipid-Derived
Quality Problems
To maintain or extend the sensory and nutritional qualities of
seafood, it is important to minimize or delay the undesirable
reactions of lipids, such as oxidation and hydrolysis. Time
is of the essence with these reactions, and thus interventions
should be done as early as possible to be able to extend
quality as much as possible. The simplest means of controlling
oxidation is maintaining low temperatures, since enzymatic
and nonenzymatic oxidation reactions are greatly influenced
by temperature (Hultin 1994). As mentioned before, very low
temperatures such as freezing will accelerate lipid hydrolysis.
However, hydrolysis as well as oxidation will be reduced if
products are kept at extremely low frozen storage temperatures
(e.g., below −40◦C) compared with conventional frozen storage
(about −20◦C or higher).
At the harvest level, bleeding fish can lead to significantly
lower levels of oxidation, since heme proteins are reduced
(Richards et al. 1998). Special care should be taken to prevent
tissue disruption in storage, since both oxidation and hydrolysis
will be increased. Washing fish fillets and fish mince will also
remove significant amounts of heme proteins (Kelleher et al.
1992, Richards et al. 1998). Another effective way to reduce oxidation
of unstable species is the removal of dark muscle, or deep
skinning. This removes not only a large fraction of the heme
proteins but also a large amount of oxidatively unstable lipids
present in the dark muscle itself and below the skin. Protection
from oxygen is another effective means for reducing oxidation.
This can be achieved through modified atmosphere packaging,
where oxygen is either reduced (for lean species) or completely
removed (for fatty species).Vacuum packaging of seafood is also
highly effective for reducing oxidation (Flick et al. 1992). Filleting
fish under water (where O2 is low) has also been reported
to lead to less oxidation on storage than filleting in air (Richards
et al. 1998). Special gases such as carbon monoxide have been
found to significantly reduce oxidation of several species, even
after fillets are removed from the gas, most likely since the gas
reduces the prooxidative activities of heme proteins (Kristinsson
et al. 2003).