Fish Processing

1. CHAPTER 2
HANDLING OF FRESH (Wet)
AQUATIC PRODUCTS
Doname A. Reyes
Instructor I
PHF 100

2. A. Spoilage of Fresh Aquatic Products
Fish and other aquatic products are among the
world’s most perishable commodities.
Spoilage in aquatic products begins soon after
death. Following the death of fish, blood
circulation stops resulting in a series of
changes within the muscle. The spoilage of
fresh fish is complicated process for which no
single factor is responsible, but, rather, it is a
combination of several interrelated processes.

3. - Bacterial and enzymatic spoilage are largely
temperature dependent.
- The higher the temperature, the faster the
rate of spoilage.
- Fatty fish spoil faster than lean fish
- Small-size fish spoil faster than large fish of
the same species.
- Cold-water fish spoil faster than warm-water
fish
- Round fish spoil faster than flat fishes.

4. What makes the fish spoil?
• 1. Bacteria
• Bacteria- microscopic one-celled organisms
which are found in the environment. The flesh
of the fish is sterile (free from bacteria) when
they are alive, but large numbers of bacteria
are normally present in the surface slime, on
the gills, and in the guts.

5. • Freshwater fishes bacteria: mesophilic-gram
positive. – 3 layers of cell wall and purple in
color
– Example: Micrococcus, Bacillus, Cornyformes

6. • Marinewater fishes bacteria:
Psychrotrophic gram-negative- 2 layers of
cell wall and pink in color.
- Example: Pseudomonas, alteromonas,
acinetobacter, flavobacterium, cytophaga
and vibrio

7. • Bacteria are normally not harmful to healthy
living fish since the fish’s natural defense keeps
them under control. But as soon as the fish dies,
the bacteria and the enzymes they secrete begin
to invade the flesh through the skin, through the
lining of the body cavity or through any puncture
in the body. Bacteria secretes enzymes, which
break down complex substances in the flesh into
simpler substances resulting to spoilage.
• Not all the bacteria present in the fish are
responsible for the spoilage of fish.

8. • In chilled fish, the most active specific
spoilage organisms (SSO) are gram-negative,
psychrotrophic rods such as Alteromonas
putrefaciens and certain Pseudomonas, Vibrio
and Aeromonas.
• Shewanella putrefaciens - a typical SSO for
the aerobic chill spoilage of many fish from
temperate waters.
• Bacterial spoilage does not start until the
passage of rigor mortis.

9. • RIGOR MORTIS – is the progressive stiffening
of muscle shortly after death. Rigor usually
starts from the tail towards the head until the
whole body becomes hard and stiff
(inflexible).

10. What makes the fish spoil?
• 2. ENZYMES
• Enzymes are protein substances present in the
muscle and in the gut of fish that initiate or
speed up chemical reactions.
• At the death of fish, the normal regulation
system stops to function and the supply of
oxygen and energy production ceases.

11. • The cells begin a new sequence of processes
characterized by the breakdown of glycogen
(this process known as Glycolysis) – the
degradation of energy-rich compounds.
• After death, the enzymes naturally act on the
food in the gut tissue.
• Autolysis – the self-breakdown or self-
digestion that results the weakening,
softening and discoloration of fish tissues.

12. What makes the fish spoil?
3. CHEMICAL SPOILAGE
• Spoilage of fish due to chemical changes
mainly occurs during storage in ice or in
frozen condition.

13. 3. CHEMICAL SPOILAGE
• 3 factors in chemical changes or rancidity of
lipids:
• 1. Lipid autolysis -enzymatic hydrolysis with fatty
acids, and glycerol as main product.
• 2. Auto-oxidation – the reaction of unsaturated
lipid with oxygen.
• Oxidative rancidity in fish can result to serious
quality problems such as rancid flavors and odors
as well as discoloration.
• 3. Denaturation of proteins during frozen storage
resulting to tough, dry and fibrous texture.

14. B. HYGIENE AND SANITATION
• HYGIENE – means the science of good health
and in everyday use, it signifies cleanliness
and freedom from the risk of infectious
diseases.
• Indicator of hygienic processes in foods:
1. absence of any food poisoning hazard
2. attractive in appearance, odor and flavor
3. presentable in customer

15. 1. CLEANLINESS
• Cleanliness is needed at every stage of fish
handling and preparation.
• Clean- means the absence of visible dirt or
unwanted matter.
• Cleaning- the removal of soil, food residues,
dirt grease or other objectionable matter
(FAO/WHO 1983)

16. • Cleaning alone, however, will not reduce the
number of microbes; hence a further
treatment called “sanitation” or “disinfectant”
is required.
• SANITATION- is the process of reducing the
number of living micro-organisms (but not the
spores) in the plant to a level judged safe by
public health authorities.
• DETERGENTS and DISINFECTANTS OR
SANITIZERS are used in hygienic cleaning
procedure.

17. • DETERGENTS – loosen and help remove dirt
such as fish slime and blood.
• SANITIZERS- kill actively growing microbes.
• Ideal detergents would be characterized by:
1. good wetting capacity
• 2. ability to remove soil from surfaces
• 3. power to emulsify (Soften)
• 4. capacity to hold material in suspension
• 5. good rinsing property
• 6. non-corrosive

18. • 7. compatible with other materials
• 8. quick and complete solubility
• 9. dissolving action on foods solids
• 10. germicidal action
• 11. complete water softening power
• 12. non-toxic
• 13. economical to use

19. • Efficient sanitizers or disinfectants do not
basically kill all micro-organisms present but
reduce their numbers to a level at which they
can reasonably presumed to present no
danger to health.
• A good sanitizer or disinfectant must possess
the following properties:
1. Effective germicide
2. Easy to dissolve in water
3. Low level of toxicity
4. Stable in concentrated form

20. • 5. Does not significantly corrode metal or
plastic
• 6. Effective at low concentrations unaffected
by water conditions
• 7. Safe to health in both concentrated and
diluted form
• 8. Deodorize
• 9. compatible with cleaning compounds
• 10. Low persistence

21. • Sanitation or disinfectant can be made by:
1. Physical treatments- such as heat, UV
irradiation, or by means of chemical
compounds.
2. Chemical Disinfectants – commonly used in
the food industry include chlorine and
cholorine compounds, iodophores, quaternary
ammonium compounds, ampholytic
compounds, peracetic acid and hydrogen
peroxide (FAO/WHO 1983)

22. C. WAYS IN PREPARING FISH
• The methods of preparing “wet” whole or
round fish either for chilling, freezing or
processing vary according to the specific
requirements of the user.
• The following are the most common forms of
preparing whole or round fish:
• 1. Drawn Fish (Gutted) – fish that has been
eviscerated or the entrails removed.

23. • 2. Dressed fish – Fish with scales, viscera, fins,
head and tail removed. It is ready to cook or
prepared particularly to improve presentation.
3. Steaks – These pieces are cross-section slices
of a large, dressed fish. A steak is usually 2-3
cm thick.

24. 4. Fillets- The meaty sides of the fish
removed from the backbone and ribs.
Fillets are practically boneless.

25. • Different kinds of fillets:
a. Block (Butterfly or double)- formed by both
sides of the fish, still joined by the uncut flesh
and skin of the belly.
b. Cross-cut fillets – from the flat fish taken
from each side as a single piece.
c. Quarter-Cut fillets – flesh from each taken
off in two pieces
d. Single fillet- just one side of the fish.
* Single, cross-cut and quarter fillets can be
skinless.

27. • 5. Sticks and Portions – sticks and portions are
small elongated chunks (rectangles) of
uniform size and thickness cut from the meaty
portion (fillet) of the fish.

28. D. Characteristics of Fresh and Spoiled
Aquatic Products
• The freshness quality and the extent of
spoilage products after harvesting and prior to
consumption are generally evaluated by using
the human senses (sight, smell and touch).

29. Characteristics of Fresh and Stale Fish
CHARACTERISTICS Fresh Fish Stale Fish
1. Odor Fishy Foul or sour
2. Gills Bright Red Light Pink
3. Slime Clear and few
on the skin
Cloudy and plenty
on the skin
4. Eyes Clear,
Transparent,
bright and
protruding
Cloudy and
shrunken

30. CHARACTERISTICS FRESH FISH STALE FISH
5. Flesh Firm and elastic;
fingermarks do
not remain
Soft and finger
marks remain
6. Skin &
Colors
Shiny and bright Dull and Pale
7. Scales Slick tightly to
the skin
Loose and
easily removed
8. Vent Pinkish or
reddish
Brownish
9. pH 6.0 to 7.0 Below 6.0
10. Water test Sink in basin of
fresh water
Float in a basin
of fresh water.

31. Handling of Fresh Aquatic Products
• 1. Fish
- Fish must be sorted according to species and
size without delay and kept at low
temperature. The fish must not be handled
frequently. Low temperature, cleanliness,
speed and care are the important factors in
maintaining the quality of newly caught fish.

32. • 2. Crabs
- Crabs must not be handled frequently after
harvest because they are very delicate.
- Adequate water circulation or seawater
exchange is necessary.
- For short-term storage, crabs can be kept in
clean moist bags or boxes but the humidity
must be high.
- Exposure to high temperature will weaken the
crabs. To prevent damage due to fighting
during transport, the crabs must be packed
closely in wet straw or shaving.

33. • 3. Shrimps
- Shrimps harvested from the wild and ponds
should be cleaned thoroughly and protected from
high temperatures. Chilling of shrimps with
crushed ice must be done immediately.
- 4. Lobsters
- If possible, lobsters must be landed alive. If
harvested alive, they should not be damaged or
stressed. They should protected from direct
sunlight and kept moist at all times.
- If dead, lobsters must be beheaded to prevent
blackening, and the tails must be washed
thoroughly in clean seawater and chilled using
crushed ice.

34. • 5. Squids and Cuttlefish
Squids and cuttlefish must be cleaned well
and stored at low temperatures. Chilling in
crushed ice or ice slurry will maintain their
freshness.
• 6. Seaweeds
Seaweeds that are harvested fresh for local
consumption should be washed in clean
seawater then packed properly in baskets with
banana leaves as covering.

35. •END…
•THANK YOU!!!