everything about microbiology of fishes and eggs

2. Fishes :
Fishes are cold blooded aquatic
animals.
They are vertebrates who breathe with
the help of gills and have a pair of
appendages or the fins. Their bodies are
streamlined and are covered with scales.
Eggs :
Eggs are poultry products obtained
from hens, duck, etc. and are also
consumed by most of the people.
It is also a reproductive cell from which
new organism develops.

4. Fishes are found abundantly in all
natural waters.
It is valuable source of food and
had been used by humans from
ancient times.
Fish is a valuable source of high
levels of protein, minerals and
vitamins.
Oily fishes are rich source of
omega-3 poly unsaturated fatty
acids.

5. Fish contamination refers to fishes that are spoiled or
infected by some sources.
Attack on fish by undesirable microorganism, for
example- bacteria, viruses, fungi, etc., from external
source is called microbial contamination of fishes.

7. a)From water
b)From intestine
c)At the time of catching
d)Microbes on slimy surface
e)From equipment
f) From fish storage
g)During transport
h)From fish processing industry

8. Fresh water contains fresh
water bacteria.
Northern waters contain
psychrophillic bacteria.
Tropical waters contain more
of mesophillic bacteria.

9. Both salt water and fresh
water fishes can contain
microorganism in their
intestine.
The intestine fluid may
contain 1000 to 100 million
bacterial load per ml.

10. The number of microorganism
on the surface of fishes are also
influenced by the way of
catching.
If some injury occurs at the
time of catching, contamination
starts.

11. The surface of fishes also contain some of the
microorganism that can cause contamination of
fishes.

12. Boats, fishing net, boxes, fish house, etc., may
be contaminated with bacteria and other
microbes and may also get transported to the
fishes.

13. Contamination of fish can also occur if
they are kept in low quality ice or in any
other storage boxes.

14. At the time of
transportation of fishes from
fishing place to markets, if the
temperature is not maintained
i.e. frozen temperature,
contamination may start.
During transportation, the
already contaminated fish
may contaminate the other
fresh fishes.

15. Fish processing instrument,
example- knife.
Fish collecting ship.
Fish processing table
Polluted environment
Auxillary gutting devices, fillating
machine, etc.
Contaminated ice
Labours

16. Fish and other sea foods may get
spoiled by:
a.Auto-oxidation (oxidation of
unsaturated fats)
b.Reaction caused by fish’s own
enzymes
c.Metabolic activities of microorganism

17. The spoilage process starts immediately after
the death of the fish.
The process involves:
Autolysis
Bacterial invasion and putrefaction
Rigor mortis

20. 1) The kind of fish
Flat fish get spoiled more rapidly that round fish.
•Undergo rigor mortis more rapidly.
•Deteriorate more rapidly because of oxidation of
unsaturated fats of their oils.

21. 2) The condition of fish when they are caught
• Fishes that are tired due to struggle, lack of oxygen and
excessive handling get spoiled rapidly.
• Feedy fishes that is full of food when they are caught are
more perishable than those with an empty intestinal
tract.
3)Kind and extent of contamination of the fish
with bacteria
• Contamination may be from mud, water, handler and
the exterior slime and the intestinal content of the fish.
• Greater the load on fish, more rapid is the spoilage.

22. 4)Temperature
•Hotter the temperature, more rapid is fish
spoilage.
5)Use of antibiotic ice and dip

23. Bright colour of fish fades and yellow or
brown discolorations occurs.
Slime on fish increases, specially gills
and flaps.
Eyes gradually sink or shrink, pupil
becomes cloudy and cornea opaque.
Gills turn light pink or greyish colour.
Reddish brown discoloration develop
towards the tail and is a result of
oxidation of haemoglobin.

25. Yellow to greenish- Pseudomonas
fluorescence, Micrococcus
Red or pink- Sarcina, Micrococcus, Yeast,
Bacillus and molds
Chocolate or brown- Yeast

27. For effective preservation, very low
temperature sometimes upto -40degree
Celsius is maintained.
In this manner the fish stays in edible
condition up to 6 or 7 months.

28. Chilling is obtained by covering the fish with
several layers of ice.
Chilling is effective for short time preservation
like transporting the landed fish to nearby markets
or to canned factories, etc.
Chilling can’t prevent spoilage altogether but in
general the colder the fish the greater is the
reduction in bacterial and enzymatic activity.

29. This is more effective than chilling.
Freezing is achieved either by using a mixture
of ice or salt or simply by refrigeration.
The recommended level at which temperature
of the fish has to be brought down is -30 degree
Celsius and the interior of the fish should be -20
degree Celsius.

30. Drying involves dehydration i.e. Removal of
moisture content of fish so that the bacterial
decomposition or enzymatic autolysis does not
occur.
 Moisture content must be reduced up to 10%
either naturally or by artificial means.

31. Salt is a preservative agent used to lengthen the
self life of the fish.
This is used in almost all methods of preservation
except icing, refrigeration and freezing.
There are different kinds of salt some being better
than the other for fish curing.
A distinction must be made between two
techniques of salting: wet salting and dry salting.

32. This is a very effective method of preservation though
costly.
Product is very good and retains much of its flavour.
Fishes are cleaned and then cut into proper boneless
pieces in the filleting plants.
The pieces are then brined or pickled to improve the
taste.
Preliminary cooking is then carried out.
Cooked pieces are then put in cans.
Sterilization is done in the final step.

33. Numerous chemical preservatives are used
to fight the perishibility of the fish.
Benzoic acid, sorbic acid, boric acid,
formaldehyde, etc., are some the examples of
the preservatives that are used successfully all
over the world.

34. Several types of antioxidants are used to
preserve fishes specially those that have high
quantity of fats.
It prevents the undesirable changes in the
unsaturated fats of the fish.

35. This is a simple method of preservation for
consumption of the fish directly after curing or within
12 hours.
Re-smoking and roasting can keep the product in a
good condition for more than 12 hours.
Salted fish can also be smoked by this method, but
this is used mostly for immediate consumption or to
bring the product in smoked form to the nearby
market.

37. EGG SHELL:
•Represents about 10% of the weight of
egg and consists mainly of calcium
carbonate and calcium phosphate.
EGG WHITE:
•Represents approximately 60% of the
weight of the egg and consists of 88% of
water and 18% of dry matter, primarily
protein.
EGG YOLK:
•Represents about 28% of the weight of
the egg and consists of approximately 2/3
fat and 1/3 of protein.

38. Most eggs are sterile, at least inside, but the shells soon
become contaminated by faecal matter from the hen, by
the cage or the nest, by the water with which they are
washed, and perhaps, by the packaging material also.
The total no. of microorganism per shell of a hen’s egg
is found to be in the range of 10^2 to 10^7.

40. May exhibit cracks, leaks, stain or dirty
spots on the exterior as well as well as “meat
spots” or translucent spots on the yolk when
candled.
From these any break in the shell or dirt on
the egg can result in its spoilage.

41. The changes that take place in egg due to
storage is due to the external non microbial
causes and those resulting from growth of
microorganisms in storage place.
This may be due to the unhygienic conditions
of the storage place, storage devices or the
labourers.

42. Untreated eggs lose weight and moisture
during storage.
Also, during storage, the alkalinity of the
egg white increases from 7.6 to may be 9.5.

43. Contaminate the egg shell.
Penetrate from the pores of
the shell to the membrane.
Grows through the
membrane towards the egg
white and may be to the yolk.

44. Green rots- Pseudomonas florescens
Colorless rot- Pseudomonas, Acinetobacter,
Alcaligens and certain Coliform bacteria
Black rots- Proteus melanovogens, Pseudomonas,
Aeromonas
Pink rots- Pseudomonas
Red rots- Serratia marcescens

45. Yellow/ blue/ green spots- Penicillin
Dark green or dark spots- Cladosporium
Pink spots- Sporotrichum
Penicillium, Cladosporium, Sporotrichum, Mucor,
Thamnidium, Botrytis, Alternaria, etc.

47. Asepsis:
Great care is taken to reduce the contamination of the
outside of the shell by hen faeces or dirt from the nest.
When the eggs are dried or freezed, care is taken to
discard those in which microbial spoilage has take place.
Proper cleaning and sanitization of equipment is done
to reduce contamination.

48. Removal of microorganisms:
Dry cleaning, as in sandblasting helps to remove lots
of dirt as well as microorganisms from the surface of
the egg.
Washing with plain warm water also helps to remove
dirt, bloom as well as some of the microorganisms.
Use of heat:
Heat can also be used for reducing the number of
microbes in egg.
The maximal time at different temperatures for
heating in water in order to just avoid coagulation, for
example, 800 sec at 57.5 degree Celsius; 320 sec at 60
degree Celsius or above resulted in some coagulation
of the white when heat treatments were employed that
would control rotting.

49. Use of low temperature:
Chilling:
For commercial storage for 6 months or longer, a
temperature of -1.7 to -0.55 degree Celsius and
relative humidity of 70% to 80% is recommended.
Freezing:
The eggs are selected by candling and then are
washed mechanically with a final rinse of 200 to 500
ppm of chlorine and then are broken on automatic
breaking machines.
They are then passed into the inspection cups
where the whites and the yolk gets seperated and
filtered, mixed or churned.
They are frozen in 30 or 50 lb tin cans or other
containers usually by a sharp-freezing process.

50. Preservation by drying:
Most of the drying of eggs utilizes the spray dryer
where the liquid is sprayed into a current of dry,
hot air.
Another method is a roller or drum process, in
which the liquid egg is passed over a heated drum
with or without vacuum.
Air drying is accomplished by means of open pans
or by the belt system where the egg is on a belt that
passes through a heated tunnel.

51. Use of preservatives:
Preservatives may be used on shells of eggs and the
atmosphere around them or on wraps or on containers of
eggs.
Chemical preservatives used are borates, permanganates,
benzoates, salicylates, etc.
Use of hot or warm solutions of hypochlorites or
quaternary ammonium compounds ,etc.
Use of irradiation:
Experiments indicate that pathogens present in eggs can
be inactivated by means of ionizing radiations.