The objective of a centralised poultry processing plant of any scale of operation is to produce material at a price which customers can afford, which is hygienic, wholesome, attractive and saleable, of consistent appearance and quality, and with a realistic shelf life. The economics of establishment and production of the poultry processing plant is outlined in Chapter 2. The main aspects of health, hygiene and sanitation is discussed in Chapter 4. The appearance of the final product is discussed below. Throughout the whole of the operation of poultry processing, these factors must be borne in mind.
The equipment described here is for broilers, chicken, turkey and geese. Other species may have special requirements. For example, stunning time may need to be increased for larger birds, quail, guinea fowl and game generally should be dry plucked. There are special plucking machines for duck.
Assuming that a consumer wishes to buy poultry, the choice of a particular product is based on its price and appearance; its convenience, shelf life, nutritive and culinary characteristics are usually based on purchasing experience. The appearance of a particular pack may also attract an undecided customer shopping for a meat product for the family.
The appearance of the product shows its size, shape and the amount of meat in relation to its fat and bone; these factors are controlled by breeding and selection of the bird and selection of the carcase at the processing plant. Product presentation ie packaging, is discussed as part of processing later in this chapter. Product appearance also shows meat colour and this, curiously, indicates to the consumer a degree of freshness and wholesomeness*. Consumers will accept poultry which is white or of a colour which is generally accepted as “right”. Consumers do not like excessive reddening and darkening of the meat, bruising, blood clots, broken bones, remains of organs and feathers, and blood drip in the pack and will reject it. These factors are affected by both pre- and post-slaughter handling which are discussed below.
Assuming that the colour, shape, size and price are acceptable, the consumer takes home the product and prepares a meal with it. At tasting, the qualities of texture, flavour and juiciness are judged. These three characteristics and that of colour are influenced by both pre- and post-slaughter handling of the bird and its carcase. As general rules, pre-slaughter handling should be carried out to cause minimum stress to properly fed but fasted birds; post-slaughter handling should emphasize clean, speedy production with rapid chilling and prompt dispatch of product.
* This may not be an accurate conclusion. A well presented, wholesome-looking pack may be positively dangerous, whereas a poor-looking pack can be of excellent quality.
Feed should be withheld from poultry for at least four hours before birds arrive at the abattoir for slaughter. Depending on distance from the slaughterhouse, poultry should be taken off their feed and water one to four hours before they are loaded and taken for slaughter. This ensures that the birds are significantly empty and their faeces are dry. If the period is extended to, say, 10 hours, the faeces becomes more fluid and the chances of cross contamination between birds during transport is increased.
Birds should be picked up gently by hand and carefully loaded into their crates. This is to avoid bruising of the flesh and breakage of bones. An excited bird may overheat which may lead to meat quality and keeping problems later. A crate of 0.8 × 0.6 × 0.3m, will hold about 10 – 12 birds. In the tropics, it is essential that the birds are not overcrowded and liable to overheat. Larger birds should be allowed more space than smaller birds.
The transport vehicle should be situated in the shade. The type of transport used will depend on the number of birds to be carried and the distance. Whether the crate is loaded on to the carrier of a bicycle, the tray of a pick - up truck, small general purpose vehicle, low loader or huge dedicated transport system, the same principles apply. The crates should be loaded onto the transport with care and properly secured. This means placing them gently on top of each other and tied to the structure of the vehicle. The crates should be stacked to allow each bird plenty of air. Adequate ventilation will reduce transport stress of the livestock. Closed sided vehicles are therefore unsuitable. The crates should be kept in the shade during transportation which should be carried out in the cool of the day. For this reason, early morning carriage is recommended.
The actual movement of the vehicle is important to reduce transport stress of the young birds. The best poultry will be produced if the vehicle is driven with skill. This means that the birds will not be subject to excessive vibration, acceleration, breaking, swerving and concerning at speed. In some countries, a “careful driver bonus” is offered if the vehicle is driven carefully.
On arrival at the abattoir, the crates should be carefully unloaded from the transport in the reception area. To keep the birds quiet, the lighting in this area and the hanging area should be subdued. After unloading, poultry should be kept for the minimum time before slaughter. It should be left in the crate, under cover, until required.
The empty crates should be returned to a wash area where they and the transport should be cleaned and disinfected before leaving the compound.
The system of operation used in the production of poultry depends very much on the nature of the market and what it requires. This varies very much throughout the world. The systems described here are for a completely cleaned out bird with head, neck and feet removed. The heart, liver, neck and gizzard are wrapped and returned to the bird as giblets and placed inside the carcase. Variations on this theme must be left to the individual operator.
Successful and appropriate packaging is necessary to assist with preservation of the product, protect it from physical damage, confine the product so that it remains intact and will pack better into larger containers, and add visual appeal so that customers will wish to buy. The package must look good in itself, so not only must it be potentially suitable and attractive but also must be applied with care. Good packaging is expensive so it must be wholly appropriate for the market. The choice is very wide. Experience shows, however, that simple, cheap packaging is all that is required in the tropics and for the sake of this document is all that will be mentioned here.
There are three types of packaging of interest to the poultry producer at these levels of throughput:
Over - wrapping: This is carried out on expanded or rigid plastic trays. The tray is over - wrapped with a clear film of high oxygen and low water vapour permeability. This method is the most popular but relies on good refrigeration and efficient distribution and product turnover.
Bag wrapping: Whole birds or portions packed on trays are placed in a clear bag which has a high oxygen and low water vapour permeability. It is sealed at the neck.
Vacuum Packaging: The use of gas-impermeable plastics reduces evaporative losses, prevents further microbial contamination and reduces proliferation of microbes already present, due to the natural production of carbon-dioxide as a result of tissue respiration. It is mainly used for the distribution of cut portions to butchers.
In some markets, the addition of a special absorbent pad of tissue is required to take up extra moisture.
Having produced a perishable commodity, it is necessary to maintain its quality by using an appropriate technology right through to the moment it is to be used. In this exercise, (apart from the New York Dressed) the poultry carcases are refrigerated immediately after evisceration. This method of preservation is seen as the best way to preserve it right into the consumers kitchen. It is necessary therefore, to develop a cold chain. The usual way to do this is to chill after slaughter, continue with chilled storage or freeze at the packing plant, distribute by refrigerated vehicle, off-load into a cold store or freeze room, display in cabinets under refrigeration and wrap the product as a form of insulation as the buyer leaves the shop. In this way the product is not left unrefrigerated for any unnecessary time. The industry has a responsibility to ensure that facilities exist into the retailers premises and to advise the customer of preservation techniques for the meat. This may mean asking the customer to use the product within a few hours.
Dispatch should be carried out quickly and efficiently. The vehicle collecting products from the poultry processing plant should be refrigerated or insulated. If the latter, it should be cool on arrival at the plant. This usually means it should arrive and depart early in the morning, convenient also for the subsequent retail trade. Once the formalities, paperwork etc have been settled, the last thing to do is load the vehicle. The vehicle doors should be opened, the chilled or frozen cartons taken directly to the vehicle, stowed, and the doors closed immediately after. The vehicle should then drive without delay to the shop, market etc where formalities should be completed before the doors are opened or after efficient removal of the cartons into a prepared cold or freezer store.
To assist with the following descriptions of slaughter and further processing, reference should be made to the appropriate drawings in the Annexes.
In some systems, birds are removed from the crates and hung on an overhead shackle where they are stunned by a low voltage system before placing in the bleeding cones.
Once it has stopped struggling, the bird is stunned with electrodes which may be either free standing or attached to a knife.
Free standing stunner
In other systems, birds are placed in the cones of the killing stand one by one and allowed to rest briefly before stunning. The head of the bird is held in one hand and the electrodes are applied. The switch is operated and the current allowed to pass through the head for about ten seconds. This induces a form of tranquillization. The bird rests perfectly still. This ensures that the feathers do not tighten and are therefore easy to remove. A knife is then used to cut the blood vessels in the neck. Practice is required to develop the technique.
The head of the bird is held in the left hand so that the left side of the neck is uppermost. The cut is started by placing the blade of the knife just behind and below the ear lobe. With the slightest downward pressure of the right hand, the knife is pulled forward for a short distance just behind the jaw bone, at the same time rolling the head slightly with the left hand to the left and inserting a little upward pressure. As soon as the cut is completed, the head is twisted slightly to see that blood is gushing out from the cut. The trachea, (wind pipe) must not be severed or the neck bone cut into as this leads to incomplete bleeding and makes plucking more difficult.
If the bird is to be used for the New York Dressed method of preparation, the cut is made inside the mouth so that there is no visible wound. The anastomosis between the two jugular veins at the base of the skull is cut.
There are other ways of stunning a bird before slaughter but they do not produce the best quality carcase. The usual way is to break the neck. Both legs are held in the left hand and the neck is held just below the head between the first and second fingers of the right. The bird is “stretched” and the head bent backwards until the neck is dislocated. The bird is then placed in the cone and the blood vessels cut with a knife.
Another stunning method is to place the bird in the cone and apply a sharp blow to the head with an iron bar or similar. There is a chance of missing however, or incompletely stunning the bird. The technique should not be used by unsupervised, inexperienced slaughtermen.
A fourth way is to place the bird in the cone and then decapitate it swiftly and completely. Although this would appear to be a quick and most effective way of slaughter, the oesophagus is left in the neck to contaminate the carcase and the head is removed, rendering a true New York Dressed carcase open to more rapid spoilage.
In Moslem countries, stunning is not permitted. In these circumstances the suspended bird is simply bled by cutting directly across the exposed throat at the base of the skull.
Birds should be allowed to bleed for 1 1/2 to 2 minutes before dressing starts.
After the bleeding period, the carcase is removed from the cone without delay and passed through the hatch, on to a holding table. A second operator takes the carcase and pulls the flight and tail feathers by hand. In turkeys and larger birds, a special machine may be necessary to remove these feathers (see photograph). The body is then applied to the dry plucking machine.
Removal of flight feathers
This machine comprises a 1.1 kw (1 1/2 hp) motor driving a shaft supported by a bearing assembly. The shaft drives a plucking head by a belt. The plucking head consists of a series of rotating plates held at an angle by a thrust plate at each end of the plate bearing. As the discs rotate they close, drag in the feathers, grip them and pull them from the bird. As they continue to rotate, they separate, and release the feathers into a collection bag to the rear of the machine. Many dry pluckers, particularly those used in higher throughput factories, are connected to a large-bore tube connected to a fan. This draws the feathers away from the plucking head and into a suitable receptacle.
The plucking action is gentle and, provided the skin is stretched tightly no damage should occur. It is important to work methodically and speedily.
Dry plucking machine and plucking head
The back of the bird is presented to the plucking head. Holding a wing in each hand and supporting the neck, the back is plucked completely. Holding the legs in the right hand and the neck in the left, the skin is stretched tightly across the breast before presentation to the plucking head. The complete underside of the carcase is plucked. Next, the back of each wing is presented to the plucking head. After plucking, the bird is allowed to drop to pluck the inside of the wing. The bird is held by one leg and allowed to swing so that this leg can freely rotate against the plucking head until the feathers are removed. This is repeated for the other leg. The area around the vent is plucked by holding the carcase in the left hand, breast uppermost and, with the right hand pulling both legs back towards the operator. The lower part of the carcase and the vent is thus presented to the plucking head. Finally, unwanted stubs are presented to the plucking head to finish the operation completely. Please see the following pictorial sequence:
The bird is then considered as New York Dressed. It should then be hung on a mobile rack, washed thoroughly in cold, chlorinated water, allowed to drain fully and air cooled for 15 minutes or so. If a refrigerator or cold store is available, the carcases should be placed in it immediately after draining. Carcases should be dispatched as soon as possible after plucking.
Mobile hanging rack
At the end of each working period the feathers should be taken through the door to reception and disposed of in a manner described in Chapter 2.
Ducks, quail, turkeys, geese or game may be wax finished. After dry plucking, the carcase is steeped in a tank of wax at a temperature of 54°C (130°F) and suspended from a rail until cool. The wax is removed by hand or by a wax stripper, which is like a drum plucker. The wax may be collected and reclaimed in special equipment. About 60% of the original wax will be recovered.
No refrigeration facilities have been installed in the smallest packing plant. Facilities for this scale are expensive to commission, operate and maintain. Experience has shown that there is consumer resistance to refrigerated meat in some areas of the world particularly where it is produced on a small scale. Experience has also shown that the faith shown by some managers in the capability of refrigeration goes beyond reasonable limits; the meat is kept there too long with subsequent product deterioration.
Having said this, the smallest plant has accommodation for refrigeration if this is seen as essential. The room before the loading bay is meant to be light, cool and well ventilated but there is no reason why it should not be refrigerated. It is believed that all birds should and will be taken away from the factory as soon as possible after slaughter.
Birds are stunned and slaughtered in a manner described for Model 1.
After the bleeding period, the carcase is removed from the cone without delay and passed through the hatch, on to a holding table. The flight and tail feathers may be removed by the machine described for Model 1. The operator will then scald and defeather the carcase.
The bird is lowered into a tank of water heated to a temperature of 51.5°C (124°F). This temperature is critical and must not exceed 53.5°C (128°F) under any circumstances. This may cause irreversible discolouration of the carcase. At a temperature of 60°C (140°F) the epidermis may be removed and considerable discolouration may be seen if the bird is allowed to dry out. The bird may be agitated now and again and feather release should be tested by occasionally pulling at a few feathers. The feathers may be released fully between 15 seconds and 2 1/2 minutes.
There is a small-scale scalding machine available which automatically agitates the carcase in the water. After bleeding, the bird is placed in a cage or basket attached to a horizontal shaft located over the scald water. Several birds may be placed in the same cage. The door of the cage is closed and the machine switched on. The axle rotates and the cage is drawn through the scald water. The machine may be governed by a timer. After scalding the carcases are removed and plucked.
Agitating carcase scalding tank
There are three ways in which feathers may be removed completely. The first, for broilers only, is by hand. The feathers are simply pulled from the carcase and placed in a feather bin. The method takes a lot of time, requires a large number of operators and is very messy. Hand plucking is generally not recommended.
The second method is by holding the carcase against rubber fingers protruding from a continuously rotating horizontal drum. The drum rotates away from the operator and the feathers follow until they are thrown clear towards the back of the machine.
The bird is held with a leg in each hand and laid firmly on its left breast on the rotating rubber fingers. It is agitated backwards and forwards to pluck the left breast and thigh. The bird is turned over to pluck the right breast and thigh. Both legs are taken in the left hand and the tail feathers gripped in the right hand before pulling them out with a twisting movement. The legs are held well apart in both hands. The bird is placed on its back on the drum and the pelvis and the back plucked. This action is continued by placing both legs in the right hand and applying a slight pressure using the left hand to the breast. The head in the left hand is placed with the legs in the right. Using the left hand to pull out the left wing into a fan, it is pushed down and inwards to strip the feathers. Change hands to pluck the right wing. The operators hands must be kept well clear of the rotating drums. Please see the following pictorial sequence:
Use of the drum plucking machine
The third method uses a bowl plucker and is depicted here and in Drawing 2 in the Annexes. Scaled birds, to a weight specified by the manufacturer, are placed in the bowl plucker chute which passes into the body of the machine.
Bowl plucking machine
After about 35 seconds, the machine is stopped (a timer can be fitted) and a door to the bottom of the machine is opened. The plucked carcases emerge ready for further processing. The time taken in the bowl plucker will depend on the nature of the bird, its age, condition etc. It is not absolutely necessary to scald birds before they enter the bowl plucker. Cold water may be introduced into the machine instead. The finish of the bird may not be as good, however, as that from scalded carcases.
After removal from the bowl plucker, some flight and tail feathers may remain on the carcase. These are removed by hand by an operator who then hangs them on a mobile rack and washes each immediately and thoroughly in cold chlorinated water. After draining, they are pushed through to the evisceration room.
Birds may be processed by another machine, called a finisher, which stubs wings and hocks. It comprises long rubber beaters attached to two horizontal shafts which rotate at a brisk pace. This machine can save the tedious work of three or four staff in larger scale operations.
The feathers from both the drum and bowl pluckers are usually thrown to the floor and require frequent removal. They are wet and most of them are relatively easy to pick up and place in the feather bin. It is the relatively few which collect in corners and around the legs of the standing equipment which cause most problems. Feathers are removed from the plucking area through the door to the reception area for disposal by one of the methods described in Chapter 2.
The bowl plucking machine is under-used at this scale of operation but produces a superior product to that of the drum plucking method for only little extra cost.
Birds arrive in the evisceration room on a mobile rack. Each rack holds about 40 carcases. There are two methods of evisceration. The first method described takes place on a table.
The carcases are removed from the rack one by one and placed on the evisceration table. The bird is placed on its back with the head hanging over the edge of the table towards the operator. A pictorial sequence of evisceration, trussing and portioning is given in Annex 6.
Carcase evisceration table
The head is removed with a knife and placed in the offal bin. The neck skin is cut from body to head. The neck is cut away from the carcase, trachea (windpipe) and crop. It is placed on a tray on the table away from the work area. The crop is placed in the offal bin.
The bird is then turned round and a sharp knife used to cut round the vent. The incision must be made carefully so that the intestines are not cut. The opening must be big enough to place a hand inside the carcase. The carcase is held firmly with the left hand (assuming the operator is right handed) and a drawing tool is placed through the cut. It is held against the breastbone of the bird and, when the end is reached, pulled down and back towards the operator so that the offal is drawn outside.
The liver, heart and gizzard are then cut away and placed in the appropriate trays on the table. The inedible offal is placed in the offal bin. The inside is then inspected for any remaining, unwanted tissue. The birds are then washed in cold chlorinated water and chilled in cooled water or slush ice.
Every so often, the edible offal (heart, liver, neck and gizzard) should be moved across to the giblet station and processed in a manner described below.
Table evisceration is not particularly clean and is actively discouraged or legislated against in some countries. Its major advantage is that it is cheap and uses very low technology. A recent development for small scale operations is the introduction of the carousel system of evisceration. It comprises a circular tray of 1.25m in diameter at waist height. A wheel is located above this tray at a height of 1.5m from which is suspended a series of poultry hangers. One to five operators stand around the carousel and eviscerate the poultry while it is suspended. This second method is described. For a throughput of 200 birds/day however, only one or two operators are required.
|Carousel and evisceration tools|
The carcases should be hung with their backs towards the operators. At the carousel, the first operator cuts the skin down the back of the neck, pulls it out and detaches it from the crop and trachea (windpipe). The crop is removed and dropped into the evisceration tray. A cut is then made round the vent with a sharp knife, taking care not to cut the intestine and making sure the cut is large enough to insert a hand inside the carcase. The next operator inserts a drawing tool through the incision keeping it pressed against the breastbone (which is away from the operator) until it reaches as far as it will go. Holding the carcase horizontally and firmly with the left hand (assuming right-handedness) the tool is pulled down and out so that the offal is drawn outside the bird. The offal is allowed to hang down the back of the bird ready for inspection.
After inspection, the third operator should cut off the liver, heart and gizzard and place them in the appropriate gizzard trays. The inedible offal is then detached allowing it to fall into the evisceration tray. The tray has a waterspray to wash the inedible offal into the offal truck situated underneath. The fourth operator should inspect the carcases and remove any lungs and other unwanted material using the serrated lung removal or other appropriate tool. The head is then cut off and dropped into the evisceration trough and the neck removed with the secateurs. It is then placed in a giblet tray.
The giblet trays holding the edible offal should be moved to the giblet station where the livers, hearts and necks are washed. The gizzards are opened with a sharp knife and then washed. The inside “skin” is removed by knife. This is not easy and, depending on the bird, it may be necessary to scald the gizzard in boiling water first.
After the offal has been cleaned and washed, it is then sorted and placed into small plastic bags and placed on trays in the chill room.
At the end of a production session, the inedible offal is wheeled away from the room through the plucking area to the outside to be disposed of in a manner described in Chapter 2. If an outside door is constructed into this room, it may be removed through this route.
If necessary, the birds are removed from the carousel. The feet may be cut off and placed in a suitable receptacle.
Empty carcases are placed into a cooling bath at the end nearest the evisceration room. The bath contains water, chlorinated to a minimum level of 50ppm, which is either cooled by a refrigeration unit attached to the bath or slush ice. As more carcases are placed in the bath they move each other along and warm the water. As the water warms or the ice melts, more is placed in the bath at the packing room end. This comes from the refrigeration machinery which runs continuously or from the nearby icemaker. The bath should be set so that it overflows at the evisceration room end. If ice is used, approximately 2kg will be required to cool each bird. The occasional assistance with movement of the carcases through the cooling medium by hand will ensure that some do not get left in the tank for an excessive period. Note also that the tank should be emptied and refilled every four hours as it becomes contaminated with blood and carcase materials (see Chapter 2).
The carcases will take about 20 – 30 minutes to cool. At the end of this time they should be removed and hung on a rack to drain completely. The time for the birds to drain will depend on the microclimate and circumstances in the poultry packing plant but, once established, should not be exceeded under any circumstances. An air conditioned room in most tropical areas may operate at about 25–27°C and as the carcases are relatively thin will soon reach this temperature if left hanging for an excessive period. The cost and effort expended in cooling the bird will then have been wasted.
For the sake of convenience, it will be assumed that whole birds only will be prepared at this throughput and the carcase will undergo further preparation at higher throughputs. Further preparation, however, may be made at any level of operation.
Giblets, wrapped as sets in plastic packets, are brought to the dressing table one tray at a time. The chilled washed carcases are removed from the rack and placed on the packing table. They are inspected for damage, poor dressing and possibly graded. The grading at this stage will be concerned with defects. These will include colour faults, bruising, blood clots, broken bones, remains of organs or feathers. If they are not to standard, corrections are made (eg removal of the odd feather, piece of lung tissue etc) or the carcases are returned to the chiller for other remedial action.
A packet of giblets is placed inside the abdominal cavity. String is used to truss the bird so that its legs, wings and breast are held in position and shown to best advantage. There are many ways to do this, one example is shown in the photographs.
Whole birds are neatly placed into a plastic bag so that the wings fit into the corners. A bag is placed over the guides of the bagging chute which serves to keep the bag open. The bird is slid down the guides and the packed carcase automatically slides off. The neck of the bag is twisted and the twist is forced through a slot in the sealer. A plastic tie is attached to the bag. Bags should not be secured with stationery staples.
Some customers require that the poultry is graded further. This might be confined to weight and perhaps some idea of meat to bone ratio. Poultry may also be priced or labelled with information which meets the local legislation plus that which the owner requests. In this instance, the owner should supply the label or agree to its appearance with the packer who will purchase and charge.
The packages are then placed into a cardboard carton or in a stainless steel mould on a trolley ready for the chill or freezing cycle. The metal tray must be of a dimension which will fit the inside of the cardboard carton. This is particularly important if the product is to be frozen. Once frozen, the meat is removed from the tray and placed directly into its cardboard carton. This will be impossible if the block is of the incorrect size. The advantage of freezing inside a metal tray is that when filled, the cardboard box itself will be in good shape, attractive, stack well and resistant to damage in subsequent handling.
The cardboard carton should have a polythene laminate inside to protect the cardboard from taking up moisture from the product. This will leave the box soggy, particularly in chilled poultry, or the product may stick to the box leaving brown cardboard on the pack. This looks bad on displayed products. Freezing meat inside its cardboard box is that it reduces subsequent handling and continues to insulate the meat between removal from the blast freezer and subsequent storage.
The facilities installed for the poultry processing plant include a chill room, blast freezer and freezer. This allows maximum flexibility for product preservation. Poultry should leave the packing room in a thoroughly chilled condition and this should be maintained until it reaches the consumer.
Packaged poultry can be taken into the chill room and stored overnight before dispatch the following day. The dimensions of the room allow for a full days production with some excess to hold stock if transport is delayed a little. Care should be taken to ensure that the store is managed according to the general principles laid down in the appropriate section in Chapter 2. Some of the poultry may be preserved frozen. The intention is that trolleys of packaged birds will be held in chill to await completion of the earlier blast freezer cycle. The trays will then be loaded into the freezer according to the manufacturers instruction and the machine switched on. The blast freezer operates at a temperature of about -40°C and the air speed is of the order of 2–4 m/s. Freezing will take about 2–3 hours. After this period, the machine is switched off, the freezer unloaded and the products quickly placed into cardboard cartons (where appropriate) and stored in the freezer room. This room operates at a temperature of about -20°C. The product will enter at a temperature of -40°C on the outside of the pack and -10°C on the inside. The freezer room allows the pack to equilibrate. The boxes should rest for about 24 hours before dispatch.
Birds are removed carefully from their crates by holding both legs and placed carefully on the overhead rail. The operator briefly holds the legs or runs his hands down the body to help quieten the bird. The overhead rail is moving at between 0.6 to 1.4m/minute. As the shackles are at 0.2m intervals, it is necessary to fill every shackle to ensure maximum production of 350 birds/hour and be able to control all subsequent operations. eg detail staff, use constant quantities of ice etc.
The birds are allowed to settle, and may be stunned using a method described earlier.
There are other forms of stunning apparatus but their use can be limited in the tropics. The most frequently found system is the brine bath which acts as one electrode and a metal bar in contact with the shackle which acts as the other. The bird is automatically lowered to the bath by a fall in the overhead rail and is stunned as soon as the head touches the brine. A guide ensures that the head comes into contact with the brine. The system works best where all the birds are of the same dimensions. This is not always found in small scale operations in the tropics and in multi-species abattoirs. Another system uses an electrified plate which is placed across the line of travel and set to come into contact with the head of the suspended bird as it passes. Sometimes a flow of water passes over the plate to improve its conductivity. The problems rest with the dimensions of the bird and the possibility of the bird receiving a shock and pulling its head away from the electrode. In these circumstances, it fails to stun the bird.
Water bath stunning cabinet
Birds are bled by a method described earlier. They should be allowed to bleed for 1 1/2 to 2 minutes before dressing starts.
The overhead rail moves the birds from the stunning/bleeding area and lowers them into a scalding tank. The speed of the rail ensures the birds are scalded for the right length of time and are sufficiently agitated in the scald water. A thermostat ensures that the temperature of the water is maintained at 52°C.
Cascade scald tank
After the birds have passed through the scalding tank they are removed from the overhead conveyors for plucking. The tail and flight feathers may be removed by the machine described above in Model 1. At a rate of 350 birds/hour hand plucking is totally impractical and machinery must be used. Two methods of plucking are described.
The first, using a drum plucker, requires a team of four operators and a drum of 1.5m in length. It comprises a horizontally mounted stainless drum from which many long rubber fingers extend. The drum rotates briskly away from the operator. This drum should have a second rotating drum with rubber fingers positioned above the other so that it is oriented rather like an old fashioned mangle. The drums should be set to leave about 10mm clearance between rubber fingers with both drums revolving. The carcase is simply introduced and turned and agitated until all soft feathers are removed. The operators hands must be kept well clear.
The second method of removing feathers is that of bowl plucker described earlier and used in Model 2. Whereas the machine was under-used in the previous example, the operation at 350 birds/hour is close to maximum operational capacity.
The cost variation between the large double drum and bowl plucking machines is marginal but the product from the bowl plucker may be better.
After removal from the bowl plucker, some flight and tail feathers may remain on the carcase. The carcase is placed on a pinning table where two staff remove any unwanted feathers. Alternatively, a finisher (see Model 2) may be used. The carcases are then hung onto another overhead conveyor which carries them on into the evisceration room. They are placed with the back towards the operators who will eviscerate them.
The feathers are collected frequently and periodically and placed in a feather bin. They are removed from the plucking area through the door near the bowl plucker for disposal by a method described in Chapter 2.
Birds arrive into the evisceration room through a hole in the dividing wall which separates it from the plucking room. They should then be eviscerated in the manner described for the carousel used in Model 2.
The evisceration table in this model has a trough rather than a circular tray. The trough has a waterspray to wash the inedible offal into the offal truck situated at the end of the evisceration trough.
The birds, which are still hanging from the overhead conveyor, then pass through the quick-clean bird washer or a washing cabinet. The first comprises two roller brushes mounted horizontally in line with the conveyor. The outside is shielded so that the wash water is contained within the cabinet. Chlorinated water is introduced through built in spray nozzles and, as the brushes rotate, they scrub and wash the carcase. Passage takes about one minute. The washing cabinet is similar except that it has a series of water spray heads instead of the brushes. After they have emerged, one operator takes the carcases off the rail, cuts off the feet, (placing them in a suitable receptacle) and either hangs the carcases onto a rack for air cooling or places them into the cooled water or slush ice tank.
Spray wash cabinet
The giblets and gizzards are handled in the same way as for model 2 except that an automatic gizzard skinner is used. The gizzard is held down over the serrated rollers which then removes the skin. The operator must take care that his hands do not come into contact with these rollers.
After the offal has been cleaned and washed, it is then sorted and placed into small plastic bags and placed on trays in the chill room.
Three systems of cooling are shown for this scale of operation. The first two, those of cooled water and slush ice cooling, follow much the same principle as that for Model 2 except that the cooling tank should have some form of device to direct the carcases through the tank. (Such devices were previously called “spin chillers”). Also, if used, ice should be added automatically from the icemaker to the cooling tank.
The second system involves the use of a chill store.
The birds should be hung with their legs removed, onto a marked cooling rack. Each rack holds about 150 birds and should take about half an hour to fill. They should be allowed to hang in the air for about 15 minutes to dry and then placed directly in a cold store. It is important that the birds are dry before they enter as this will not happen in the cold room where the relative humidity is high.
The chill store will require special management to ensure that the racks already inside are removed in the order in which they entered. In this way each bird will get a constant amount of cooling.
The chill store should be designed to cool four racks, each of 150 birds (say 300 kg) ie a total of 1200kg, from 35°C to 5°C in two hours.
Once cool, the birds must be processed speedily as they will soon rise in temperature (see Model 2).
Carcases may be prepared as whole birds as described for Model 2. Other methods of preparation may be undertaken according to customer requirements. This may include cutting into halves, quarters, legs, thighs, wings, breasts, drumsticks or complete deboning. Photographs of a potential cutting method is given in Annex 6.
The instruments used in preparing chicken portions include cleavers, knives, secateurs and special machinery, an example of which is shown below. This machine has an arm which points horizontally towards the operator. It has a groove on the top into which a rotating knife fits. The carcase is pushed over the arm into the knife and the two pieces fall to the side.
Deboning at a throughput of 350 birds/hour is not to be recommended. It produces bones and trim for which a system of disposal is required. The quantity produced will be small and complete burial is the only realistic disposal method. Nevertheless, where it is a requirement, complete deboning is carried out using a knife. Deboning by hand, using no implements at all, is possible. It is quick and clean but takes a lot of skill.
Poultry portions are treated in much the same manner as the whole birds but the use of trays is much more prevalent. Drumsticks, chilled or frozen in a loose plastic bag have little visual appeal whereas the same product neatly arranged on a tray with a clear overwrap has a much better chance of sale.
Again, The packages are placed on a stainless steel tray on a trolley, or into a cardboard carton ready for the chill or freezing cycle.
At this scale of operations, chill storage facilities are not provided as it is assumed that all birds will be frozen. If there is a requirement for chill storage, the building can be redesigned easily to accommodate such facilities. The system of operation will be similar to that described for Model 2.
There are some differences in operation at the increased scale, however. Instead of storage at chill temperatures before loading the poultry into the blast freezer, marked trolleys of packaged meat are taken straight from the packing room into the blast freezer room. Here they are held until frozen before removal and storage in the freezer. There is an area where the metal trays can be emptied and the product placed in cardboard outer covers. A high degree of management of product is necessary to ensure that each trolley receives the appropriate time of blast freezing. Too little time will lead to deterioration of the product. Too much is a waste of resources.