(c) The lapse of time after death. Long voyages from the fishing
grounds provide a longer time for bacterial growth.
(d) The type of sanitation practiced aboard ship and at processing and
handling facilities. Bacterial build-up on the unclean surfaces of equipment can be
tremendous and can contaminate an otherwise excellent product.
(e) Putrefaction can be retarded by thoroughly washing and gutting the
fish and removing the gills. Freezing stops it entirely as long as the fish is frozen solid.
Fish left whole, just as they come from the waters (Form I), are more liable to
putrefaction than those gutted at sea.
(4) End products. The most frequent end product of decomposition is
ammonia, a breakdown product of the protein nitrogen of the flesh. Ammonia is evolved
rather slowly at first and may not be readily noticeable. In the advanced stages of
decomposition, larger quantities are produced and a sharp odor of ammonia is
noticeable. The most common odor of stale fish is trimethylamine. Trimethylamine
(TMA) is produced by the action of bacteria on trimethylamine oxide which is present in
the nitrogenous compounds of fish flesh. The odor of hydrogen sulfide (rotten egg) is
not typical of spoilage of fish flesh.
1-11. FISH CLASSIFICATION
Based on the deteriorative condition, Table 1-1 provides a list of the
characteristics that can be used to determine the condition of a fish product (fillet or
steak). The three conditions are fresh, stale, and putrid.
1-12. PARASITES OF FISH
a. Five Parasites. There are many parasites in fish. Most do not cause
diseases in humans and are killed by normal cooking temperature and freezing. There
are only two that could cause a potential public health problem and three of commercial
importance, because they affect the quality of fish flesh presented to consumers.
(1) European or broad tapeworm. The fish tapeworm (broad or European
tapeworm) is identified by its segmented body and broad head. It is mostly found in the
U.S. in pike and pickerel fish from midwestern or Canadian lakes. It is also found in
some European freshwater fish. The tapeworm is found in cyst form in fish flesh.
However, in man, it may grow to its adult size of 20 to 30 feet. Infection (called
diphyllobothriasis) is the result of eating raw or inadequately-cooked fish containing the
cyst of the Diphyllobothrium latum. Proper preparation will render the cyst harmless.