An assignment on Spoilage of Fish and Delaying Spoilage
Introduction
Of all the food items we eat and see around us, fish spoils most quickly. The chemical composition of fish, qualities of inherent proteins and lipids and most of all, the nature of habitat where it lives, all contribute considerably to make it susceptible to spoilage soon after death. Since it is a food item and it undergoes post-mortem spoilage very quickly, the fishermen, traders and processors should carefully consider all sorts of possible measures to delay or stop such spoilage. A review of knowledge on fish spoilage will help to identify affordable quick measures that can delay the spoilage and improve the quality and shelf life of fish. Knowledge on general principles of fish processing/preservation is also important, on the basis of which such fish spoilage is stopped or delayed.
Why does a fish spoil?
Fish lives in water. There are millions of very small organisms, called bacteria, in the water that can come in direct contact with fish. Water passes through the mouth and gills during respiration. Marine fish drinks water, so these bacteria may enter the stomach. Thus the whole body of fish (skin, eyes, mouth, gills, and stomach) is exposed to bacteria. Most of these bacteria are harmless: some of these are of use to fish, some breakdown vegetation in the soil to release nutrient to the water, but some cause disease in fish and some also spoil fish (Clucas and Ward, 1996). The spoilage bacteria, however, cannot spoil the muscle when the fish is alive. After death, spoilage bacteria enter the muscle from the skins and gills, disintegrate the muscle cells and take necessary energy to grow. As soon as fish dies, the supply of energy ceases. The fish muscles gradually harden and the entire body becomes stiff within a few hours of death. This hardening remains for a couple of hours depending on the species, temperature and other conditions at death.
After stiffing, the muscles become soft again, from when spoilage starts (Love, 1992). Chemicals, namely enzymes that are present in the muscle, viscera, digestive tract and that produced by bacteria breakdown the muscles into smaller components. The production of acids in the muscle increases, whereby spoilage bacteria from surface, gill and gut attack and feed on such smaller components and spread out. Increased bacterial activity results in a heavy slime on the skin and gills and an unpleasant sour odour with soften muscle tissue. During this time fish lipids are broken down by the action of oxygen of the air that may result off flavour and color changes. By this way spoilage accelerates in fish with the lapse of time at room temperature.
Factors and causes of fish spoilage
Energy prod. stops
Blood circulation stops
Oxygen supply fails
Respiration ceases
Death of fish
Acid forms in muscles
Muscle stiffing
Tissue breakdown
Bacterial growth
Muscle softing
Aerial oxidation
Fish spoils for three reasons
o Action of enzymes
o Action of bacteria
o Oxidation of lipid
If disease producing bacteria contaminate the fresh fish, it can cause serious illness or even death of the consumers. If the fish are kept clean and properly iced, bacterial contamination can be kept to a minimum and growth of any bacteria can be reduced.
Bacteria and enzymes cannot spoil fish if. they do not get adequate environment. Both bacteria and enzyme need certain congenial conditions under which they are most active. Both of them like warm temperatures: not too cold and not too hot. Bacteria like to have water present for it to survive. They also need to have a substrate (food) on which to be active- in this case the flesh of fish.
How does spoilage accelerate?
Spoilage of fish is accelerated by
· struggle/excitation during fishing
· rough handling: injury or damage of muscle
· contamination
· delay of icing
· exposed to sun at any stage
How can we delay or stop fish spoilage?
Fish spoilage can be delayed or stopped by
· Protecting fish from physical injury or muscle destruction
· Applying proper sanitation and avoiding contamination
· Lowering temperature immediately: keeping cool during transportation and storage
· Destroying enzyme and killing bacteria by high temperature: canning, heat processing (fish ball, fish sausage, fish stick, burger, etc.)
· Reducing water content in fish body: drying, salting, smoking
Any delay of cooling down the temperature will mean that fish can continue spoiling. The rate of bacterial reproduction and growth, digestion of the flesh by gut enzymes and the oxidation of fish body lipid depend on temperature. Therefore, lowering of temperature will slow down the spoilage caused by any of the three means discussed above. Moreover, lowering of temperature extends the lag phase of microbial growth that delays the development of rapid growth and reproduction of bacteria
How can we protect fish from physical injury?
· To protect fish from physical injury or muscle damage
· Be careful on handling fish during harvest, keeping in fish hold, taking out of fish hold, unloading and transportation;
· Do not throw fish; do not stand on fish;
· Do not mishandle fish in any way that might bruise flesh, split skin or burst gut;
· Do not pack too tight / too large volume;
· Do not stack ice/fish mixture too great a depth;
· Do not overfill boxes;
· Remove damaged fish;
· Use finely-crushed ice, no rough-edged large ice pieces
How can we maintain proper sanitation?
For maintaining proper sanitation in post-harvest handling, preservation and transportation --
· To acquire good knowledge on sanitation and contamination;
· Wash everything with clean/ chlorinated water;
· Use clean place and container to keep fish
· Prepare ice from clean water;
· Avoid contamination from guts and rotten fish;
· Keep small fish apart from large fish;
· Keep separate catch caught different times separately;
· Keep fish of soft bellies separately;
· Remove guts and wash out traces of guts in body cavity;
· Wash fish hold, deck and ice chamber of boat thoroughly;
· Do not put fish on the ground;
How can we lower the temperature of fish immediately?
Temperature of fish can be lowered by -
o Icing of fish with ice crystals;
o Chilling of fish with other means (dry-ice, liquid nitrogen, etc.);
o Dipping fish in cool brine/ RSW/CSW;
o Freezing of fish
From the above discussions, it is clear that the fish processing or preservation is to be done on the basis of certain principles in order to stop or delay the spoilage immediately in the muscle tissue. Four principles are generally involved in the preservation/processing of fish and shell fish by various methods
General principles of fish preservation/processing
I. Prevention or delay of microbial decomposition
a. By keeping out micro-organisms (asepsis)
b. By removal of micro-organisms. e.g. through filtration
c. By hindering the growth and activity of micro-organisms
- low temperature (chilling, super-chilling, freezing
- irradiation (gamma rays)
- modified atmosphere (nitrogen, carbon dioxide, carbon monoxide, oxygen, etc.)
drying and dehydration, cold smoking, other curing methods
- other treatments like hypobaric storage. ozone, blanching, chemicals, etc.
d. By killing the micro-organisms
· heat treatment
· canning, hot smoking
· irradiation
· heat processing of fish paste: boiling, broiling, grilling,
· microwave and retort heating, etc.
· surimi based products, kamabokos
· fish ball and fish sausage
2. Prevention or delay of self-decomposition of fish
a. Removal of digestive segments of fish by dressing,
b. Destruction or inactivation of fish enzyme:
- blanching
- heat treatment: modori, inhibition of serine and cysteine protease
c. Prevention or delay of purely chemical reactions:
- prevention of oxidation by antioxidants, smoking, anaerobic conditions
3. Prevention or delay of rancidity
a. By lowering temperature
b. By reducing or hindering contact of air through packaging or brining, glazing.
c. By removing or reducing lipid content
d. By using chemicals, antioxidants
4. Prevention of damage due to insects, animals, rodents or other biological means.
a. By cleaning and keeping clean of factory premises
b. By fixing fly/mosquito proof nets.
c. By protecting drainage mouth, holes, ventilators, out lets of the building by wire-mesh covers, nets, etc.
Conclusion
A review of knowledge on fish spoilage will help to identify affordable quick measures that can delay the spoilage and improve the quality and shelf life of fish. Knowledge on general principles of fish processing/preservation is also important, on the basis of which such fish spoilage is stopped or delayed.
Introduction
Of all the food items we eat and see around us, fish spoils most quickly. The chemical composition of fish, qualities of inherent proteins and lipids and most of all, the nature of habitat where it lives, all contribute considerably to make it susceptible to spoilage soon after death. Since it is a food item and it undergoes post-mortem spoilage very quickly, the fishermen, traders and processors should carefully consider all sorts of possible measures to delay or stop such spoilage. A review of knowledge on fish spoilage will help to identify affordable quick measures that can delay the spoilage and improve the quality and shelf life of fish. Knowledge on general principles of fish processing/preservation is also important, on the basis of which such fish spoilage is stopped or delayed.
Why does a fish spoil?
Fish lives in water. There are millions of very small organisms, called bacteria, in the water that can come in direct contact with fish. Water passes through the mouth and gills during respiration. Marine fish drinks water, so these bacteria may enter the stomach. Thus the whole body of fish (skin, eyes, mouth, gills, and stomach) is exposed to bacteria. Most of these bacteria are harmless: some of these are of use to fish, some breakdown vegetation in the soil to release nutrient to the water, but some cause disease in fish and some also spoil fish (Clucas and Ward, 1996). The spoilage bacteria, however, cannot spoil the muscle when the fish is alive. After death, spoilage bacteria enter the muscle from the skins and gills, disintegrate the muscle cells and take necessary energy to grow. As soon as fish dies, the supply of energy ceases. The fish muscles gradually harden and the entire body becomes stiff within a few hours of death. This hardening remains for a couple of hours depending on the species, temperature and other conditions at death.
After stiffing, the muscles become soft again, from when spoilage starts (Love, 1992). Chemicals, namely enzymes that are present in the muscle, viscera, digestive tract and that produced by bacteria breakdown the muscles into smaller components. The production of acids in the muscle increases, whereby spoilage bacteria from surface, gill and gut attack and feed on such smaller components and spread out. Increased bacterial activity results in a heavy slime on the skin and gills and an unpleasant sour odour with soften muscle tissue. During this time fish lipids are broken down by the action of oxygen of the air that may result off flavour and color changes. By this way spoilage accelerates in fish with the lapse of time at room temperature.
Factors and causes of fish spoilage
Energy prod. stops
Blood circulation stops
Oxygen supply fails
Respiration ceases
Death of fish
Acid forms in muscles
Muscle stiffing
Tissue breakdown
Bacterial growth
Muscle softing
Aerial oxidation
Fish spoils for three reasons
o Action of enzymes
o Action of bacteria
o Oxidation of lipid
If disease producing bacteria contaminate the fresh fish, it can cause serious illness or even death of the consumers. If the fish are kept clean and properly iced, bacterial contamination can be kept to a minimum and growth of any bacteria can be reduced.
Bacteria and enzymes cannot spoil fish if. they do not get adequate environment. Both bacteria and enzyme need certain congenial conditions under which they are most active. Both of them like warm temperatures: not too cold and not too hot. Bacteria like to have water present for it to survive. They also need to have a substrate (food) on which to be active- in this case the flesh of fish.
How does spoilage accelerate?
Spoilage of fish is accelerated by
· struggle/excitation during fishing
· rough handling: injury or damage of muscle
· contamination
· delay of icing
· exposed to sun at any stage
How can we delay or stop fish spoilage?
Fish spoilage can be delayed or stopped by
· Protecting fish from physical injury or muscle destruction
· Applying proper sanitation and avoiding contamination
· Lowering temperature immediately: keeping cool during transportation and storage
· Destroying enzyme and killing bacteria by high temperature: canning, heat processing (fish ball, fish sausage, fish stick, burger, etc.)
· Reducing water content in fish body: drying, salting, smoking
Any delay of cooling down the temperature will mean that fish can continue spoiling. The rate of bacterial reproduction and growth, digestion of the flesh by gut enzymes and the oxidation of fish body lipid depend on temperature. Therefore, lowering of temperature will slow down the spoilage caused by any of the three means discussed above. Moreover, lowering of temperature extends the lag phase of microbial growth that delays the development of rapid growth and reproduction of bacteria
How can we protect fish from physical injury?
· To protect fish from physical injury or muscle damage
· Be careful on handling fish during harvest, keeping in fish hold, taking out of fish hold, unloading and transportation;
· Do not throw fish; do not stand on fish;
· Do not mishandle fish in any way that might bruise flesh, split skin or burst gut;
· Do not pack too tight / too large volume;
· Do not stack ice/fish mixture too great a depth;
· Do not overfill boxes;
· Remove damaged fish;
· Use finely-crushed ice, no rough-edged large ice pieces
How can we maintain proper sanitation?
For maintaining proper sanitation in post-harvest handling, preservation and transportation --
· To acquire good knowledge on sanitation and contamination;
· Wash everything with clean/ chlorinated water;
· Use clean place and container to keep fish
· Prepare ice from clean water;
· Avoid contamination from guts and rotten fish;
· Keep small fish apart from large fish;
· Keep separate catch caught different times separately;
· Keep fish of soft bellies separately;
· Remove guts and wash out traces of guts in body cavity;
· Wash fish hold, deck and ice chamber of boat thoroughly;
· Do not put fish on the ground;
How can we lower the temperature of fish immediately?
Temperature of fish can be lowered by -
o Icing of fish with ice crystals;
o Chilling of fish with other means (dry-ice, liquid nitrogen, etc.);
o Dipping fish in cool brine/ RSW/CSW;
o Freezing of fish
From the above discussions, it is clear that the fish processing or preservation is to be done on the basis of certain principles in order to stop or delay the spoilage immediately in the muscle tissue. Four principles are generally involved in the preservation/processing of fish and shell fish by various methods
General principles of fish preservation/processing
I. Prevention or delay of microbial decomposition
a. By keeping out micro-organisms (asepsis)
b. By removal of micro-organisms. e.g. through filtration
c. By hindering the growth and activity of micro-organisms
- low temperature (chilling, super-chilling, freezing
- irradiation (gamma rays)
- modified atmosphere (nitrogen, carbon dioxide, carbon monoxide, oxygen, etc.)
drying and dehydration, cold smoking, other curing methods
- other treatments like hypobaric storage. ozone, blanching, chemicals, etc.
d. By killing the micro-organisms
· heat treatment
· canning, hot smoking
· irradiation
· heat processing of fish paste: boiling, broiling, grilling,
· microwave and retort heating, etc.
· surimi based products, kamabokos
· fish ball and fish sausage
2. Prevention or delay of self-decomposition of fish
a. Removal of digestive segments of fish by dressing,
b. Destruction or inactivation of fish enzyme:
- blanching
- heat treatment: modori, inhibition of serine and cysteine protease
c. Prevention or delay of purely chemical reactions:
- prevention of oxidation by antioxidants, smoking, anaerobic conditions
3. Prevention or delay of rancidity
a. By lowering temperature
b. By reducing or hindering contact of air through packaging or brining, glazing.
c. By removing or reducing lipid content
d. By using chemicals, antioxidants
4. Prevention of damage due to insects, animals, rodents or other biological means.
a. By cleaning and keeping clean of factory premises
b. By fixing fly/mosquito proof nets.
c. By protecting drainage mouth, holes, ventilators, out lets of the building by wire-mesh covers, nets, etc.
Conclusion
A review of knowledge on fish spoilage will help to identify affordable quick measures that can delay the spoilage and improve the quality and shelf life of fish. Knowledge on general principles of fish processing/preservation is also important, on the basis of which such fish spoilage is stopped or delayed.