spoilage of fish and other sea foods

1. Spoilage of Fish and other
sea foods
BANGARU KARTHIK
M Sc Micro biology

2. Contamination
• Depends on the microbial content of water
in which they live
• Common genera are:
• Pseudomonas, Acinetobacter, Moraxella,
Alcaligens, Micrococcus, Flavobacterium,
Corynebacterium,Sarcinae, Serratia, Vibrio,
Bacillus

3. Microbes in different waters
• Northern waters - Psychrophiles
• Tropical waters – Mesophiles
• Fresh waters – Aeromonas, Lactobacillus,
Brevibacterium, Alcaligens, Streptococcus
• Intestine of fishes: Alcaligens,
Pseudomonas, Flavobacterium, Vibrio,
Bacillus,Clostridium, E.coli

4. Number of organisms
• Slime layer – 100 to million per sq.cm
• Intestinal fluid – 1000 to 100 per million
• Gills tissue – 1000 to 1million per gram

5. Different org in different sea foods
• Oyesters & other
shelfish
• Alcaligens,
Flavobacterium,
Moraxella,
Acinetobacter

6. • Shrimps, crabs &
Lobsters
• Bacillus, Micrococcus,
Pseudomonas,
Acinetobacter,
Moraxella,
Flavobacterium,
Alcaligens, Proteus
Shrimps
crabsLobsters

7. spoilage

8. Spoilage is due to……..
• Autolytic enzymes
• Oxidation
• Bacterial activity

9. • Fish flesh is more perishable because of
more rapid autolysis by fish enzymes
• Unsaturated fish oils seems to be more
susceptible to oxidative deterioration than
other animal fats
• pH of fish has an important influence on its
perishability, the lower the pH, slower will
be bacterial decomposition

10. Factors influencing kind and
rate of spoilage

11. • The kind of fish
• Condition of the fish when caught
• Kind and extent of contamination of the
fish fresh with bacteria
• Temperature
• Use of antibiotic ice or dip

12. The kind of fish
• Flat fish spoil more rapidly than round fish
Round fish
Flat fish
1. Under go rigor mortis more rapidly
2. Deteriorate rapidly because of oxidation of
unsaturated fats of their oils
because

13. Condition of the fish when caught
• Fish that are exhausted as a result of
struggle, lack of oxygen and excessive
handling spoil rapidly
• Feedy fish i.e., full of food when caught
are more perishable than those with an
empty intestine tract

14. Kind and extent of contamination
of the fish fresh 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

15. Temperature
• Chilling the fish delay bacterial growth
• Warmer the temperature, shorter the
storage life of fish

16. Use of antibiotic ice or dip
• Enhances the self life of fish

17. Evidence of spoilage
• It is very difficult to detect the spoilage of
fish by seeing it
• Many tests such as ……..
• Test for volatile acids
• Volatile bases
• pH
• H2S
• Ammonia
Are too slow to be useful. So, no particular test does
not exit that fish is spoiled

18. External changes
• 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

19. • Gills turn light pink and grayish color
• Reddish brown discoloration develops
towards the tail and is a result of oxidation
of hemoglobin
• Sequence of odours develop
Fresh --- Sea weedy --- sickliy sweet---
stale fishy---ammonical--- putrid

20. Gills turn light pink

21. Bacteria causing spoilage
• Predominant organisms vary with
temperature
• At chilling temperature: Pseudomonas,
Acinetobacter, Moraxella, Flavobacteria
• At high temperatures: Micrococcus,
Bacillus

22. Why fish spoils very soon ?
• Fish consists of non-protein nitrogen and
autolytic changes caused by their enzmes
increase the supply of nitrogenous
compounds
• Eg: amino acids, amines and glucose
From these compounds
Bacteria make trimethylamine, ammonia, amines
putrefaction
results

23. Discoloration of fish
River rot

24. Yellow color of the fish
• Pseudomonas fluorescens, Yellow
micrococci

25. Red or pink color
• Sarcina, micrococcus,
Bacillus

26. Choclate brown color
• Asporogenous yeast

27. Spoilage of special kinds of fish
and sea foods
Salt fish Salt tolerant or halophilic bacteria- Micrococcus,
Serratia, Bacillus, Alcaligens, Pseudomonas
Smoked fish molds
Crab meat Pseudomonas, Acinetobacter, Moraxella,
Proteus
lobsters Pseudomonas, Bacillus, Alcaligens,
Flavobacterium
Shell fish Acinetobater, Moraxella, Vibrio, Flavobacterium,
Bacillus
Crabs &
oyesters
Vibrio including vibrio parahaemolyticus

28. oysters
• Remain good till they are at chilling temperature
• Oyesters are high in protein and also contain
sugars, which result from hydrolysis of glycogen
• At temperature near freezing
• Pseudomonas, Acinetobacter, Moraxella, Flavobacterium,
Micrococcus
• Souring is due to proteolysis

29. Thank You