Fish, when freshly caught, is relatively
wholesome. The quality of the fish
starts to deteriorate as soon as it is taken from the water. The principal cause of fish condemnation is
decay. Factors influencing the rapid
spoilage of fish are:
- Microbial – several species of
microbes are always present in the surface slime and intestinal tract of
the healthy fish. As long as the
fish remains alive, these are held in check and the flesh of the healthy
fish remains sterile. However, as
soon as the fish dies, these reproduce rapidly and attack all the
constituents of the tissues. Since these
organisms live on the cold-blooded vertebrate at low ocean temperatures,
they are able to resist ordinary refrigeration temperatures. If microbial decomposition must be
retarded, fish, upon being caught, should be immediately stored at
temperatures below 0ºC.
- Physiological – due to the fight
and consequent exertion when caught, glycogen in the muscles is depleted
or nearly so. There is therefore
little glycogen to convert into lactic acid in slowing bacterial growth in
muscles is limited.
- Chemical – besides bacteria,
enzymes act upon certain constituents of the fish, breaking it down into
simpler substances. This is called
self-digestion or autolysis. The
growth and activities of certain bacteria on the surface of the fish
produces undesirable chemical substances called trimethylamine which is
responsible for the fishy odor of spoilt fish. This chemical then diffuses into the
flesh of the fish causing spoilage.
Characteristics of Good Wet Fish
Characteristics of Stale Wet Fish
- Clear, bright, slightly protruding eyes with black pupils.
- Gills are bright red in color, odorless and usually closed.
- Moderate amount of natural slime covering fish, skin shiny and
color unfaded, scales are strongly adherent, creamy white or transparent
- Flesh is firm to the touch, solid, opaque, elastic and strongly
attached to backbone.
- Abdomen clean and free from offensive odor. Belly walls are firm with no
- Blood along the backbone in the visceral cavity is bright red.
- Pleasant odor (briny)
- Body stiff and tail rigid.
- The carcass will sink in water.
- Dull, sunken grey eyes which will disappear in extremely rotten
- Gills are of very pale pink or dark brown color, slimy and have
- Natural slime is yellowish and has a bad odor, dull appearance,
many missing scales as they are easily detached from the skin.
- Flesh is soft and limp, transparent and pits easily on pressure
and can be easily loosened from backbone.
- Abdomen discolored with offensive odor, belly wall soft and
- Blood along backbone is dark to black in color, with foul odor.
- Strong rank odor, progressing into a putrid, rotten fish odor.
- Body limp and pliable.
- The carcass will float in water.
of Fresh Fish
1. Minimum handling – the less handling
fish receives, the longer it will remain wholesome and the less likelihood of it
causing fish poisoning.
2. Fresh fish should be buried in ice
that is relatively finely ground or shaven.
3. It is poor practice to allow fish
fillet, sliced fish or fish with flesh exposed to come in direct contact with
water or ice as this will spoil the flavour and appearance and result in a
soggy unpalatable product.
4. Refrigeration is necessary at all
times to keep down bacterial action and autolysis.
Smoked Fish (Herring)
1. Flesh should be firm, dry and free
2. Flesh should have fresh, clean,
1. Flesh is sweaty, soft and slimy.
2. Flesh is moldy and has bad odor.
1. Flesh should be firm, clear in colour, fairly dry on
surface, neatly trimmed.
2. Always stored in dry cool place.
3. Free of insect pests and dirt. Bad Fish
- Flesh is discolored, (pink fungus growth).
- Wet and moist saltfish not properly stored.
- May be infested with Lasioderma or other pests.
1. Fish should be covered with clean liquor.
2.Odor should be pleasant, pickle odor.
3. Fish should be firm and free from bloodstained and broken
- Fish only partially covered or covered with muddy liquor.
- Foul or rancid odor
- Fish is bloodstained, discolored and broken into pieces.
The outside should be clean and
free from dirt, with shells tightly closed.
When a handful is rubbed
together, they will sound like pebbles.
They will sink in water and has
a pleasant odor.
If the pH of the liquor is
tested, it will be between 6 and 7.
The liquor appears milky
especially during the spawning season (spring).
Shell not closed.
When shaken, does not have a
pebble like sound.
Unpleasant odor, excessive dirt
PH of the liquor more acidic
and has an opaque appearance.
has a black or dark ring in the
inside of the shell
Floats in water.
Oysters removed from shell should be stored
in sterile containers and if being kept for over 4 days, should be stored at
30ºF or below.
Source: Marcia Reid
(lecturer at University of Technology, Jamaica. Lecture notes.)
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