This document discusses contamination, preservation, and spoilage of fish. It notes that fish can become contaminated from various sources like water, handling equipment, storage, and transport. Several bacteria are identified as common contaminants. Preservation methods discussed include chilling, freezing, drying, salting, canning, use of preservatives, antioxidants, and smoking. Proper preservation helps extend the shelf life of fish by slowing bacterial growth and enzymatic activity.

1. Contamination, preservation,
& spoilage of fish
SUBHANANTHINI JEYAMURUGAN,
18PY17, M.SC., MICROBIOLOGY.
AYYANADAR JANAKI AMMAL COLLEGE SIVAKASI.

2. Introduction
• Fish is found abundantly in all natural water.
• It is a valuable source of food & has been used by man
from ancient times
• Fish is a valuable source of high quality protein, minerals
and vitamins
• Oily fish are rich in omega-3 poly unsaturated fatty acids

3. Contamination
• Fish contamination refers to fishes that are spoiled or
infected
• Attack on fish by undesirable microorganism (bacteria,
fungi, yeast, mold, virus or other toxins & by products)
from external source is called microbial contamination
of fish.

4. Contaminating microorganisms of fish

5. Contaminating microorganisms of fish

6. Contaminating microorganisms of fish

7. Source of contamination
From water
From intestine
At the time of catching
Density microbes in surface slime
From equipment
From fish storage
During transport

8. From water- spoilage
Fresh water fish carry fresh water
bacteria.
Northern water carry mostly
psychrophilic bacteria.
Tropical water carry more mesophiles
bacteria.

9. From intestine
Both salt water and fresh water fish
contain bacteria in the intestine.
The intestine fluid contains 1000 to
100 million bacterial load per ml

10. At the time of catching
The numbers of microorganisms on
the skin of the fish can be
influenced by the method of
catching
If some injury have done at the
time of catching fish contamination
may start

11. Density microbes in surface slime
The slime that covers the outer
surface of fish has been found to
contain bacteria.

12. From equipment
 Boats
 Catching net
 Boxes
 fish house and fisher may be
contaminated with bacteria & may
transport into the fish during cleaning.

13. From fish storage
Contamination in fish can be
started from when it kept in ice
due to low quality of ice or the
storage.

14. During transport
At the time of transporting fish from
fishing place to shelling market, if
the temperature is not maintained
that is frozen temperature,
contamination may start.
During transporting, contaminated
fish may contaminate the fresh fish.

15. Contamination of fish in fish processing industry:
Contamination may occur from-
 Fish processing instruments
 Fish collecting ship
Fish processing table.
 The polluted environment of that processing
industry.
Auxiliary gutting device ( Used to clean fish and
their Gut), Filleting machine etc.
 Contaminated ice may contaminate fish at the time
of freezing.
Microbial contaminants may come from laborer. If
they are not neat and clean.

16. Spoilage of fish
Food spoilage can be considered as any change that render
the product unacceptable for human consumption.
Fish & other sea food may be spoiled by
Autoxidation (oxidation of unsaturated lipids)
Reaction caused by activities of the fish’s own
enzymes
Metabolic activities of the microorganisms

17. Types of spoilage
Microbial spoilage
Physiological spoilage
Biochemical spoilage

18. Process of spoilage
The spoilage process starts immediately
after the death of fish
The process involves
Autolysis
Bacterial invasion & putrefaction
Rigor mortis

19. Enzymatic spoilage
Autolysis

21. Factors influencing kind & rate of spoilage
The kind of fish
The kind & extent of contamination
of the fish with bacteria
Use of an antibiotic ice or dip
The condition of the fish when
caught
Temperature : 0ᴼ- 1ᴼ

22. 1) The kind of fish
Flat fish spoil more rapidly than round fish because
Under go rigor mortis more rapidly
Deteriorate rapidly because of oxidation of unsaturated fats
of their oils

23. 2) The condition of fish when caught
Fish that are tired as a result of struggle, lack of
oxygen and excessive handling spoil rapidly
Feedy fish that is full of food when caught are more
perishable than those with an empty intestine tract

24. 3) Kind and extent of contamination
of the fish with bacteria
Contamination may be from mud, water, handler and
the exterior slime and intestinal content of the fish
Greater the load on fish, more rapid the spoilage

25. 4) Temperature
 Chilling the fish delay bacterial growth
 Warmer the temperature, shorter the storage life of fish
5) Use of antibiotic ice or dip
Use of antibiotic ice or dip

26. Evidence of spoilage
Bright color of the fish fades and dirty
yellow or brown discoloration appears
 Slime on fish increases , especially flaps &
gills
 Eyes gradually sink and shrink, pupil
become cloudy and cornea opaque
Gills turn light pink and grayish color
 Reddish brown discoloration develops
towards the tail and is a result of oxidation of
hemoglobin

27. Bacteria causing spoilage:
At chilling temperature-
Pseudomonas,
Achromobacter,
Flavobacterium.
At ordinary
atmospheric temp-
Escherichia,
Proteus, Serratia,
Sarcina and
Clostridium.
At higher
temperature-
Micrococcus and
Bacillus.

28. Discolorations of fish
Yellow to greenish – Pseudomonas fluorescence,
Micrococcus
Red or pink – Sarcina, Micrococcus, Bacillus, Yeast &
Mold
Chocolate or brown – Yeast

29. Preservation
methods of fish

30. Use of low temperature
 for the effective preservation, very low temperature to the tune of
-40°C and maintained at -23°C approved.
This way, fish stays in food condition for about 6- 7 months

31. chilling
Chilling is an obtained by covering the fish with layers of ice.
Chilling is effective for short term preservation suck as is needed
to the transport landed fish to nearby markets or to canning
factories etc.
Chilling cant prevent spoilage altogether but in general the colder
the fish the greater the reduction in bacterial in enzymes activity.

32. Freezing
This is more effective than chilling.
 freezing is achieved either by using a mixture of ice and salt or
refrigeration.
 the recommended level at which the temperature of the fish has to be
brought down is -30°C and the interior part of the fish has to be -20°C.

33. Drying
Drying involves dehydration i.e., the removal of moisture contain
of fish so that the bacterial decomposition or enzymatic autolysis does
not occur. Moisture contains should be reduce up to 10% either
naturally or by the artificial means.

34. salting
 salt is the preservative agent used to lengthen the shelf life of fish and
fishery products.
 this is used in almost all methods of preservation except in icing,
refrigeration and freezing.
There many different kinds of salt, some being better than others for fish
curing.
A distinction must be made between the two chief techniques of salting:
wet salting and dry salting.

35. canning
 this is a very effective method through costly.
Product is very good and retains much of flavor.
Fish is cleaned and then cut to proper boneless pieces in filleting plants.
The pieces are then brined or pickled to improve taste.
Preliminary cooking is then put in cans.
Cooked pieces are then put in cans.
Final cooking combines sterilization with stream and high.

36. Preservatives
Numerous chemicals are being used as preservatives to fight the great
perishability of fish.
Benzoic acid
Sorbic acid
Boric acid
formaldehyde

37. Antioxidants
Several types of antioxidants are being used to
preserve fish specially on those kinds which are fatter
then others. It prevents undesirable changes in the un
saturated fat of fish.

38. Smoking
 This is a simple method of preservation, for consumption either
directly after curing or within 12 hours.
Re smoking and roasting can keep the product in good condition for a
further 12 hours.
Salted fish can also be smoked by this method, but this is used mostly
for immediate consumption or in order to bring the produce in smoked
form to a nearby market