Catching
How to maintain freshness
The decline in freshness
1.Assessing freshness
Squid are generally transparent immediately after capture,
and their backs are dark brown and the chromatophores in the
epidermis are active. The transparency is gradually lost and
the meat becomes tinged white, but the pigment in the epidermis
is still yellow-red-brown. The squid meat then becomes rigid,
since the chromatophores become fixed in the open state when
squid are exposed to air and lose their moisture. If the squid
are maintained in the wet state, the chromatophores gradually
contract and the surface becomes white with black spots. The
surface of fresh squid becomes white when processed with ice
water. Then, the amount of volatile basic nitrogen in the epidermis
increases, the pigment is eluted, the body color becomes tinged
with red, and the meat decays.
2. Change in meat quality
In general, the amount of volatile
basic nitrogen in squid meat readily increases during storage,
in contrast to fish meat, and the pH readily rises. The squid
meat is rich in nitrogen extract, thereby facilitating bacterial
propagation, and the amount of trimethylamine oxides is high.
Moreover, squid meat consists of arginine and proline. Arginine
is known to rapidly decompose when ground squid meat is stored
at low temperatures, and this is one cause of alkalization
of squid meat. The result is 'slimy' skin, which is unacceptable
to consumers.
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