BIOCHEMISTRY OF
THERMAL-PROCESSED
PRODUCTS
Exposure of the fish to elevated temperatures is detrimental to
tissue structure, and results in very undesirable effects (Haard
1994). Extreme texture softening in fish has been attributed to
cysteine proteases acting on the fish muscle at elevated temperatures
(Konegaya 1984). Heat-stable alkaline proteases and
neutral proteases (modori or gel-degradation) are active when the
temperature reaches 60–70◦C (Lin and Lanier 1980, Kinoshita
et al. 1990). Degradation of connective tissue of mackerel appears
to be associated with muscle proteases and pyloric ceca
collagenase (Pan et al. 1986).
The rate of oxidation of desirable myoglobin and oxymyoglobin
of the red muscles of tuna to brown metmyoglobin depends
on the species of the fish and on the storage temperature
(Mattews 1983). Color deterioration in iced and frozen stored
bonito, yellowfin, and skipjack tuna caught in Seychelles waters
was demonstrated in this study.
Food biochemistry plays a role in the production of thermally
processed seafood. During the canning of seafood, it is a
common practice to precook the raw materials, for example,