Cxu

Venting \

Opening cuts \

Viscera drawing \

Inspection \

Giblet salvage-

Lung removal \

Head removal \

Crop and windpipe removal \

Washing \

Chilling-

Chilling

Packaging \

Distribution and further processing

Figure 1. Unit operations in poultry processing.

involved (eg, according to the Jewish laws known as kosher processing, stunning is prohibited). When stunning is used, it is done by electrical current passing through the bird; the amount of current and duration depends on the size of the birds. In the case of broilers, a current in the range of 60 V for 5 to 10 s is common. It is important not to use too much current, since it can completely stop the heart activity. Gas stunning (by C02, argon) is also possible (4) and has the advantage of reduced bruising of the birds.

Stunning, besides calming the birds, also helps in relaxing the muscles holding the feathers, which later facilitates feather removal.

The slaughtering itself can be done in different ways. The most commonly used method is the so-called modified kosher where the jugular vein is cut just below the jowls so that the esophagus and windpipe remain intact. According to the true kosher slaughtering procedure, the windpipe should pop out, and the whole procedure should be performed by a qualified person (shochet) and not by a machine. Decapitation and piercing through the roof of the mouth and brain are two other slaughtering methods that are seldomly used in Europe and North America today. After slaughtering, appropriate time should be allowed for bleeding since an excess amount of blood in the muscles will result in discoloration. About 35 to 50% of the total blood is removed during this stage, and it has been shown that the kosher or modified kosher slaughtering methods result in higher bleeding than decapitation.

Scalding is the process of immersing the birds in warm water to loosen the feathers. There are three commonly used temperatures for this purpose (Table 3), and they depend on the degree of difficulty in removing the feathers. The higher scalding temperature is the best for loosening feathers, but it is also the most harsh on the skin. In the case of the hard scalding, the outer layer of the skin (epidermis) is removed during plucking and the skin becomes discolored if dehydrated after processing. However, this method is the only satisfactory way to release the feathers of waterfowl. Relatively speaking, hard scalding does not cause as much discoloration in the thick skin waterfowl as it does in other poultry. Subscalding can remove part of the outer layer of the skin and leaves the skin sticky but will not result in excessive discoloration if the birds are kept in a moist environment. Semiscalding is used for young birds. It does not damage the outer layer of the skin while still allowing for relatively easy removal of the feathers in young birds. A true kosher processing, where scalding is prohibited, usually results in more skin tears because more force is required in the defeathering process. In large processing plants feather removal is done by large mechanical pickers equipped with rubber fingers that rub the feathers off the carcass. This is usually done while the carcass is hanging upside down and carried by a shackle line through the picker. The defeathering process can also be done in a batch-type operation by placing the carcasses in a drum equipped with rubber fingers. In small-scale operations, hand picking of the feathers is sometimes used. When pinfeathers are a problem (as with waterfowl), wax dipping after the picking process is common. Suspending the carcasses in hot wax, followed by cold water immer-

Table 3. Recommended Scalding Schedules for Defeathering

Scalding

Water

Time

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