POST HARVESTING PROCESSES
CHAPTER
TWELVES
POST
HARVESTING PROCESSES
12.1 CONCEPTS AND
PHILOSPHY OF POST HARVEST TECHNOLOGY
Post-harvest fisheries
entails all steps, process and or activities immediately after catch handling
and transportation processing and distribution of fish and fishery product
where if control is not applied post-harvest losses will occur.
Post –harvest fish losses are a major concern and occur in
most fish distribution chains throughout the world. Not only do losses
constitute lost income to fishers, processors and traders, they also contribute
food insecurity i.e a loss of fish means less fish available for the consumer.
POST HARVEST PROCESSES:
Fish are highly perishable. A central concern of fish
processing is to prevent fish from deteriorating .
Causatic factors of fish spoilage
1. High moisture content. 2. High fat content. 3. High protein content.
4. Weak muscle tissue. 5. Ambient temperature. 6. Unhygenic handle.
Process of fish spoilage
It involves three stages: 1.
Rigor mortis. 2. Autolysis. 3. Bacteria inversion and putrefaction.
12.2 FISH
PROCESSING
Reasons for fish processing
1. To avoid or prevent
spoilage of fish. 2. To reduce fish
wastage.
3. To extend shelf life. 4. To reduce or avoid bacterial
infection.
5. Enhance acceptability. 6. Preserves the product. 7. Ensure consumer safety.
FISH PROCESES CAN BE DIVIDED
INTO TWO
1.
Primary processing : it involved in the degutting,
filleting and freezing of fish for onward distribution to fish retail and catering outlets.
2.
Secondary processing : they produces chilled, frozen and
canned product for the retail and catering trades
TYPICALLY HANDLING PROCESSES:
The fish caught by a fishing
vessel need handling so they can be stored safely until the boat lands the fish
on shore.
The handling process are :
1.
Transferring the catch from the fishing gear (such as
a trawl, net, or fishing line) to the fishing vessel.
2.
Holding the catch before further handling.
3.
Sorting and grading.
4.
Bleeding, gutting and washing.
5.
Chilling .
6.
Storing the chilled fish.
7.
Unloading or landing the fish when the fishing vessel
returns to port.
12.3 CLEANING PROCESS
OF FISH
1.
DEGUTTING
:-
Fish gutting begins with careful descaling
from the tail to the head, then cutting it with a knife from a small
hole in the stomach along the entire body length to the head remove the gills
and use them to remove the gut.
DEGUTTING
2.
DEGILLING:- This is
done either by a rotary wire brush or a
paddle wheel which brushes the gill from the body shell
DEGILLING
3.
DESCALING (FISH WITH SCALE):- Is a
cleaning process of removing scale from a fish skin. it is also known as
scaling a fish
DESCALING
4.
FILLETING :– Fish is
filleted by cutting from the head lengthwise to the tail realising the tail
from the tail bones, raise it, up and return with the knife carefully along the
back.
FILLETING
5.
STEAKING:- Is a process
by which large fish are slices cross sectional after these processes washing
with clean water takes place.
STEAKING
Materials for cleaning
processing are: knife, scrapper, basins, tables, cutting slabs.
12.4 POST HARVEST
TECHNOLOGY OPERATION
Post-harvest fisheries involves all steps, processes or
activities immediately after catch, handling and transportation, processing and
distribution of fish and fishery product where if control is not applied
post-harvest losses will occur. Post
harvest fish loss (PHFL) refers to fish that is either discarded or sold at a
relatively low price because of quality deterioration or owing to market
changes. This means that fish operation (fishers, processors, traders and other
stakeholder involved in ancillary operations) lose potential income. Post harvest
fish losses are often caused by biochemical and microbiological spoilage change
that occur in fish after death. After a fish dies its defence mechanisms stop
and enzymatic, oxidative and microbiology spoilage set into cause quality
deterioration. Several factors tend to influence the rate of spoilage of fresh
fish:
1.
Time between death and final use or consumption.
2.
High temperatures such as 200c create
conditions for fish spoilage.
3.
Poor handling practice
MAIN TYPES OF FISH LOSSES.
There are three types of fish
losses that affect stakeholders:
1.
Physical loss
2.
Quality loss
3.
Market force loss
1.
PHYSICAL LOSS:- Physical
fish loss refers to fish that after capture or landing is not used. It is
either thrown away accidentally voluntary or as authorized. Physical loss can
cause by theft by insects eating the fish or by bird or animal predation.
2.
QUALITY LOSS:- Quality
loss refers to fish that has undergone changes owing to spoilage or physical
damage and has suffered quality deterioration. Such fish is sold for a lower
price than that which would have been achieved if the fish were of “best
quality”.
3.
MARKET FORCE LOSS:- This is a
loss caused by unexpected market demand and supply situation. These cause operators to sell
their product at a price below expectations. The loss is the difference between
the expected price and the actual price. These types of fish loss discuses
above occur throughout the post-harvest chain from harvesting to consumption.
These result in lost income and contribute to food insecurity.
12.5 THE
POST-HARVEST OPERATION IN FISHERIES ORGANOLEPTIC
ASSESSMENT:
Organoleptic
assessment or sensory assessment is the use of one or more of the five senses
to judge or form and opinion on some aspect of quality. The senses are sight,
smell taste and hearing.
The parameters used in
assessing fish and fish product quality are texture odour, colour and taste.
QUALITY EVALUATION USING PANEL OF ASSESSORS AND
HEDONIC SCALE
The food manufacturer has to
produce a product at a quality which will satisfy;
a.
The customer and (b) statutory food legislation.
In many ways the quality requirement of the customer are more
difficult to satisfy since the customer assesses the quality of a product
entirely by subjective means. The sensory evaluation of a food’s appearance,
colour, odour, taste and texture plus the visual appearance of its packaging
and presentation.
Hence, it is the responsibility of the manufacture to develop
methods which can as accurately as possible evaluate the sensory properties of
a fish which the customer finds important. This will often mean using
subjective methods of testing such as sensory {taste panel} method or in some
cause it may be possible to use objective method. Moreso, it must be remembered
that objective measurement of food quality are preferable only if the objective
test can provide a precise measure of the subjective quality being considered.
SENSORY METHODS
A sensory
method is one in which subjective measurements are made by individuals.
Numerical scoring system may be developed for such method or method of ranking
or result may be expressed simply in attribute form e.g pass/fail, acceptable/
defective
OBJECTIVE METHODS
An objective method uses a calibrated
scientific instrument to measure a specific quality parameter usually on a
numerical scale:
i.
Physical
changes:- e.g measurement of conductivity using the torrymeter
ii.
Chemical and
biochemical test e.g
Ø Test
dependent on bacterial action such as estimation of trimethylamine
Ø Test
dependents on autolytic action such as enzymic assays of nucleotide breakdown
product e.g hypoxanthine
iii.
Bacteriological
changes e.g counting and
identification of various micro organism.
ASSESSORS AND TASTE PANEL
In fishing
vessels, owner of a small buying, processing and retailing or catering business
are usually the only person responsible for quality assessment.
Similarly ,inspection of
production lines of fish product by company require a sensory accessory or
sensory expert which have undergone trainee and have a wealth of experienced
which can make acceptable and objective judgment of quality. At times, when, it
is necessary to avoid this dependence by arranging for each sample to be
assessed by more than one assessor in doing so the risk of mistakes arising
from the use of one assessor is reduced and the assessment made more reliable.
Groups of assessor operating in this way are usually referred to as taste panel
USE OF RIGOR
MORTIS
Today’s modern fishing
industry is the scene of a different battle. Here, suppliers are fighting to
deliver the freshest fish possible to customers. However, the industry faces a
problem from nature’s hand; once the fish is caught an killed the rigor mortis
gradually sets in. this means that within two to ten hour the fish will become
as stiff as a board. For during rigor mortis, fish are practically impossible
to process, and this means waiting up to five days before boning and filleting
can begin i.e removing the skeleton and not least all the tiny bones in the
surrounding flesh.
Factor determines the rate in
onset and resolution of rigor is:
a.
Temperature
b.
Handling
c.
Size
d.
Physical conduction for the fish
The technological significance of vigor mortis is of major
importance when the fish is filleted before or in rigor. In rigor the fish body
will be completely stiff, the filleting yield will be very poor, and rough handling can cause gaping. If the
fillets are removed from the bone pre-rigor the muscle can contract freely and
the fillet will shorten following the onset of rigor. For instance, if the fish
is cooked pre-vigor the texture will be very soft and pasty, the texture is
tough but not dry when the fish is
cooked in rigor while In post –rigor the flesh will become firm, succulent and
elastic.
12.6 METHODS OF PRESERVATION
Fish is one of the highly
perishable food items which spoiled rapidly by the infection of micro organism.
In light of this fish preservation is necessary in order to reduce spoilage
TYPE OF PRESERVATION OF FISH
1.
Chemical method
2.
Physical method
I.
CHEMICAL
METHOD OF PRESERVATION:- Is the application of different types of
chemical substance in preserving fish from bacterial and microorganism e.g
benzoic acid, benzoate and nitrite etc
II.
PHYSICAL
METHOD OF PRESERVATION:- Is also very common and some are very popular
to fisher man and their stake holders e.g are drying and dehydration, canning,
freezing, salting frying, smoking etc.
1.
SALTING :- Salt elements will lower
the water content below the point where bacterial or microorganisms can no
longer live and grow. In time that water passes out from the tissues of the
salt will going to penetrate the fish tissues until the salt solution filled it
in this is called as the ‘osmosis’ absorption process.
2.
SUN-DRYING:- This is a technique which
involves the removal of water content from fish tissues until the moisture of
the fish is extracted. In this process the growth of microorganism is
prevented. This can be done naturally using the heat of the sun. it is called
solar drying.
3.
SMOKING:- This is another method in
fish preservation. This process give the fish a desirable flavor and odour as
well as preserving it. Smoking is usually done through four processes. First is
cleaning the fish second is brining which is soaking the fish in a brine
solution. The third is drying and the fourth one is smoking the fish.
Fish smoking
Activities that should be carried out on
fresh fish before smoking.
Dressing( beheading, gutting and cleaning),
washing, splitting( butterfly style), salting, draining, rinsing in fresh
water, air drying.
The
following materials are required for the smoking of fish- Kitchen Knife, bowl,
basket, smoking tray, smoking kiln and salt.
Advantages of smoking fish.
1.
It is in edible form. 2. It is
preserved. 3. Value has been added.
4.
CANNING:- It is the process of
preservation by which the fish are packed in tin or glass container capable of
being sealed air tights, heated sufficiently to destroy the spoilage organism
within the container and cooled rapidly.
5.
FREEZING:- This is a techniques in
which low temperature preservation of fish that can ensure very long shelf life
and can also provide a processed product very much similar to fresh fish.
6. CHILLING:-
This is a process a fish is placed in ice to cool it or reduce its temperature.
Differences
between chilling and freezing of fish
|
CHILLING |
FREEZING |
|
1. Short time storage |
Long time storage |
|
2. Storage temperature oC |
Storage temperature well below zero e.g -30oC |
|
3. Relatively cheap. |
Relatively costly. |
|
4. Relatively low- tech. |
Relatively high- tech. |
|
5. Product resembles fresh fish. |
If poorly done can badly affect quality. |
|
6. Low skills required. |
High skill required. |
|
7. Generally
static operation |
Portable refrigeration. |
7. FRYING:- This is another method of
fish preservation like smoking, frying also give a pleasant odour and
desireable taste as well as preservation. This is done by frying the fish in
hot oil.
12.7 EQUIPMENT USED IN FISH PRESERVATION
There are several equipment
used in fish preservation processes. This equipment is as follow:
1.
SOLAR DRYER:- These are
devices that use solar energy to dry substances especially food. There are two
general types of solar dryers. Direct and indirect.
Direct solar dryers expose
the substance to be dehydrated to the direct sunlight. They have a black
absorbing surface which collects the light and convert to heat the substance to
be dried is placed directly on this surface. These driers may have enclosures
glass cover or vent to in order to increase efficiency.
In indirect solar dryers:-
the black surface heats incoming air, rather than directly heating the
substance to be dried. This heated air is then passed over the substance and
exist through a chimney, taking moisture from the substance with it.
2. DEEP FREEZER:- The deep
freezer process converts most of the water in the fish into ice. During the
first stage of cooling, the temperature falls fairly rapidly to just below 00c,
the freezing point of water. As more heat requires to be extracted during the
second stage, in order to turn the bulk of the water to ice, the temperature
changes by a few degrees and this stage is known as the period of thermal
arrest when about 60% of the water is turned to ice, the temperature again
begins to fall rapidly and during third stage most of the remaining water
freezes.
PACKAGING
MATERIALS FOR FISH.
1.
Nylon/ polythene bags 2. Cardboard. 3. Basket. 4. Can or Tin. 5. Aluminium foils
6. leaves 7. Cartons/ papers.
12.8 MARKETING
DISTRIBUTION CHANNEL OF FISH IN NEGERIA
Marketing serves as integral aspect of fish production
because it is only when the fish reaches the final destination (consumers) that
production might be complete. Marketing has been understood to be all processes
involved from the production of any commodity until it get on the final
consumer.
MARKETING CHANNEL
Marketing channel is defined
as path between production and consumption. It can also be defined as the
linkage which the fish or fish products move from the point of production to
the point of consumption.There are two classes of market channel
1.
Centralized
marketing channel:- This is where in which commodities are assembled
in large central terminal market where they are purchased by wholesalers or
processed or from farmer agent.
2.
Decentralized
marketing channel:- In decentralized it doesn’t have large
assembly-marketing facilities and traders buy directly from farmer.
In Nigeria, the channels of distribution and other aspect of
fish marketing vary widely from place to place, patterns also differ with that
of products (fresh, iced, or smokes) marketed as well as with the types of
production (artisanal industrial or aquaculture).
ILLUSTRATION OF DISTRIBUTION NETWORK
Artisanal fisheries
Fish---fisherman---middleman wholesaler---retailer (fish mummy)---consumer
Industrial fisheries
Frozen fish fresh/iced
Fishing company/importer
Factory/commercial agents
Wholesaler
Retailer(fish mummy)
Consumer
Aquaculture
FUNCTIONS OF MIDDLEMEN IN
DISTRIBUTION CHANNEL OF FISH IN TROPICAL AREA.
1.
The scattered nature of artisanal fishermen requires
the need of middlemen to make fish available to other part of the country.
2.
There are usually poor communication facilities
between the fishing settlement and urban centre.
3.
Since many fishermen depends on the middlemen’s
credit to be able to maintain their business e.g buying net, repairing cause
etc.
Agents involved in fish marketing
i. fish farmers/ fishermen ii.
brookers/ wholesalers iii.
cooperative society
iv. hoteliers and restaurants v.
local marketer vi. retailers
PROBLEMS
FACED BY ARTISANAL FISH MARKETERS PROBLEMS IN NIGERIA.
The problems of marketing
fish are compounded due to high perishable nature of fish. There are many
constrain faced by the artisanal fish marketers among them are:
1.
Lack/ inadequate
information of the fisher men: the least informed party is the
fishermen because of the physical isolation from the. Market and because there
is no radio broadcast carrying information on whole sale price.
2.
Inadequate
funding:- This is another factors which weaken the fishermen’s
bargaining position are his dependency on credit.
3.
Unorganized
nature of fisher man:- The artisanal fishermen usually used traditional
boat and hence their catch is small, which poses marketing problems.
4. Lack of storage facilities:- There are no cold storage facilities at landing centre which make the fishermen to sell their fish at low price to the middlemen.
STRUCTURE QUESTIONS
1. Which of the following occurs to fish flesh after death (a) Conservation (b) preparation (c) deterioration (c) preservation (e) protrusion
2. After death fish flesh is highly (a) perishable (b) prepared (c) preserved (d) processed (e) protruded
3. Which of the following is not used for processing fish? (a) Basin (b) knife (c) table (d) slabs (e) grater
4. The following price ensure fish quality except (a) de-gilling (b) de-gutting (c) de-moulding (d) washing (e) de-scaling
5. Which of the following does not affect fish deterioration after death? (a) bacteria (b) fungi (c) salt (d) enzymes (e) insects
6. The major concern and occur in most fish distribution chain throughout the world is (a) marketing (b) processing (c) catching (d)post-harvest fish lost
7. Post-harvest fisheries entails all except (a) processing (b) deworming (c) handling (d) transporting
8. Which of the following is not a primary processing of fish (a) degutting (b) freezing (c) frozen (d) filleting?
9. A process by which large fish are slice cross section is known as? (a) Steaking (b) Degutting (c) Degilling (d) Demoulding
10. Fish is filleted by cutting from (a) The head lengthwise to the tail (b) The tail lengthwise to the head (c) A small hole in the stomach along the entire body (d) None of the above.
11. Factors contributing to fish spoilage include the following, except (a) colour (b) handling (c) size (d) temperature (e) species
12. Which of the following equipment is not used for preservation? (a)
freezer (b) oven (c) kiln (d) refrigerator (e) silo
13. Cropping
in fishery means the process of (a) Breeding (b) Harvesting (c) Producing (d) Rearing
(e) feeding
14. The
ancient method of food preservation include (a) Pasteurization and
sterilization (b) Canning, blending and irradiation (c) freezing and boiling
(d) drying smoking and fermenting
15. A
chemical method of fish preservation is (a) using formalin (b) sun drying (c)
using benzoate (d) Using metacine
16. The
term used in describing fish that is sold at relatively low price due to
quality deterioration is (a) fishing vow (b) pot harvest fish loss (c)
deteriorating loss (d) none of the above
17. The
factors determines the rate in onset and resolution of rigor is (a) temperature
(b) size (c) handling (d) all of the above
18. The
parameter used in assessing fish and fish products quality are as follow except
(a) odour (b) taste (c) texture (d) none of the above
19. The
path between production and consumption is (a) market price (b) marketing
channel (c) commodity line (d) fiscal policy
20. The
biggest problem encounter by artisanal fisherman is (a) information (b) poor
transportation (c) storage facilities (d) funding.
21. An
example of processed fish products is (a) canned fish (b) Chilled fish (c)
Frozen fish (d) Iced fish.
22. Packaging
materials of fish include (a) Basket (b) Mat (c) Plates (d) Sieves.
23. The effect of chilling of fish on ice is that it
(a) improves the aroma of the fish (b) Keep the fish fresh for some days (c)
Improves the taste of the fish (d) Makes the fish easy to transport.
24. Which
of the following activities is involved in fish processing? (a) Chilling (b)
Freezing (c) Frying (d) Gutting.
25. Smoking
of fish could be classified as a (a) Harvesting method (b) Preservation method
(c) Feeding method (d) Stocking method.
26. Which
of the following materials could be used to package smoked fish? I. Cane basket
II. Leather bag III. Polythene bag. (a)
I and II only (b) I and III only (c) II and III only (d) I, II and III.
27. Which
of the following is not involved in fish processing (a) Decapitation (b)
Degilling (c) Degutting (d) Dessication.
28. The
act of removing fish gills and gills components is called (a) Decapitation (b)
Degilling (c) Descalling (d) Filleting.
29. Factors
contributing to fish spoilage include the following except (a) Colour (b)
Handling (c) Size)(d) Species.
30. The
acts of cutting out the insides of a fish is called (a) Degilling (b)
Decapitation (c) Filleting (d) Descaling.
31. Which
of the Following is a sign that fish is not fresh? (a) Gills are bright red (b)
Eyes are sunken (c) Fins and scales are moist (d) Flesh is firm.
32. Trash
fish are (a) Inedible (b) Edible but have no consumer demand (c) Chicken feed
(d) Popular.
33. The
most important concern when storing fish and shellfish is (a) Temperature (b)
Storing in proper container (c) Storing it below other perishable food (d)
Storing it near food.
34. Dragging
the back of a knife over the skin of a fish will remove the (a) Fins (b)
Viscera (c) Gills (d) Scale.
35. The
act of removing fish skin during processing is called (a) Defining (b) Despining
(c) skinning (d) grading.
36. Which
of the following is not a reason for processing fish? (a) Enhances
acceptability (b) Retards shelf life (c) Retards microbiological activities (d)
preserves the product.
THEORY
1. State five reasons for fish processing.
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2. Enumerate five
processes involved in fish post harvesting.
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3. Enumerate five methods of preserving fish.
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4. Define the following post – harvest activities:
(a) De-scaling
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(b) De-gutting
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(c) De-gilling.
_________________________________________________________________________________________________________________________________________________________________________________
5. List five materials
required for the smoking of fish.
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
6. Draw a suitable diagram to show the marketing channels
of farmed fish.
7. List three materials used for packaging fish.
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
8 Mention
six activities that should be carried out on fresh fish before smoking.
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______________________________________________________________________________________________________________________
9. Distinguish between chilling and freezing as used in
fish preservation.
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10. List five agents of
fish marketing.
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11. Specimen A is FRESH FISH and specimen B is SMOKED FISH.
(a) Outline the steps involved in converting specimen
A to B.
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(b) Name four by-products of
specimen A.
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(c)
State one use of each of the by-products name in (b) above.
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12. Briefly explain the three main type of fish losses.
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