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|Neck slitting and foot removal|
metal slope (wires) or by their heads passing through an electrically charged water bath with a variable voltage. The length of the water bath depends on the desired stunning time and line speed. Stunning with the normal mains frequency can result in bone fractures and in slight haemorrhages. That is why a high-frequency stunner is used with a frequency between 50 and 400 Hz.
Recent research has shown that it is more humane to kill the birds in the stunner than just to stun them.
The birds now pass along a bleeding tunnel for at least 2 minutes for turkeys and at least 90 seconds for domestic fowls. This is to allow the birds to bleed before entering the scalding process. It is estimated that 50% of the blood is removed.
The time in the scald should be no more than 2 minutes. This ensures that the skin will be untorn and unblemished. The scalding loosens the feathers for the plucking process. Sometimes detergents are added to the scald water, making the penetration of the water to the feather follicles much easier.
The first post-mortem inspection takes places in this area. Rejected birds are removed from the line.
To accelerate the removal of energy from muscles, electrical current pulses are applied to the carcass after plucking. The birds are then washed by overhead sprays.
• Head removal:
The heads are generally removed mechanically by traction of a head puller. After proper positioning the head and trachea puller breaks the spine at its weakest point after which the head, crop, oesophagus and trachea are stretched out.
Scissors cut a round vent in order to remove the intestines from the carcass. Great care is needed in this important operation as faecal contamination of the carcass, edible offals and operators’ hands has to be avoided.
All of the viscera are drawn out of the body cavity, leaving them hanging from the carcass ready for inspection. The drawing is done either by hand or by operators using eviscerating forks or by automatic eviscerating machines.
At this point the inspectors examine the viscera, the body cavity and the carcass generally. Good lighting, properly directed into the body cavity is essential.
Some machines separate the viscera pack immediately from the carcass after drawing. The viscera packs can then be examined more quickly and under more hygienic conditions.
• Removal of offals:
The edible offals, i.e. the heart, liver and gizzard are removed for further cleaning and washing. The intestines, proventriculus and lungs are discarded into the water trough or mechanical conveyor. On some lines a suction tube is then introduced into the body cavity to remove any contamination or portions of lungs remaining.
When the viscera pack is already separated automatically, all operations on the pack can also be carried automatically. This results in a higher heart and liver yield and better microbiological quality.
An inspector or a quality control officer then examines the carcass generally, especially the body cavity.
• Neck removal:
The necks are removed by cutting through the vertebrae between the shoulders using automatic or manual scissors. The necks are classified as part of the edible offal or giblets.
• Line washing:
Before going into the washing and cooling tanks the birds are spray washed to remove blood and extraneous matter.
• Polyphosphate injection:
When polyphosphates are used, they are injected under pressure by guns with two hollow perforated needles. The solution is injected into the breast and sometimes also into the leg muscles. Up to 5% of the body weight of this permitted additive solution may be injected.
Chilling can also be achieved by accurately directed flow of cold air or by water film chilling, based on the evaporation of moisture which remove the heat from the carcass.