To produce a quality poultry meat product from a live bird involves a series of efficiently performed, specific tasks in a sanitary manner. Before broilers can be processed, they must be caught, cooped, transported and held, then unloaded at the processing plant. Inside the processing plant, broilers are hung on shackles, stunned, bled, defeathered, eviscerated, inspected, chilled, graded, packaged and shipped. Because of the complexity of production and processing procedures, several factors may reduce carcass yield, carcass grade and the company's overall profit margin.

Defects resulting in carcass downgrading and product losses are caused by diseases, damage to the bird before slaughter, or maladjusted equipment and manual errors during processing. This publication focuses on those problems during processing and will assist management and supervisory personnel in reducing carcass downgrades. Tables 1-3 serve as quick reference guides for problems observed during processing.

Catching, Cooping and Transporting Live Broilers

At the grow-out house, market-age broilers are caught by the live haul catch crew, loaded into coops and transported to the processing plant. During catching, minimize bruising because it results in carcass downgrading and yield loss. Ninety per cent of bruising occurs within 12 to 24 hours before processing. Areas most frequently bruised are the breast (42 per cent), wings (33 per cent) and legs (25 per cent).

Good live haul procedures can reduce bruising and the number of birds that are dead-on-arrival (DOAs) at the plant. The distance that broilers are transported before processing affects carcass contamination and yield. Broilers that are transported long distances (six hours) have fewer bruises due to confinement, and the fatigue from travelling makes them less active during slaughter. However, the stress associated with transporting slows digestive tract clearance and increases the live shrink (live weight loss).

Receiving, Holding and Unloading Live Broilers

When birds arrive at the plant, they need adequate ventilation in the holding area to minimize mortality and excessive live shrink. Broilers should arrive at the plant and be scheduled for processing eight to 12 hours after their last feeding. This decreases the amount of material that could potentially contaminate the carcass during processing by allowing adequate time for the bird's gastrointestinal tract to become empty. Birds that go without feed for long periods of time (greater than 13 to 14 hours) begin to lose the mucosal lining of their intestines and will have lower carcass yields at slaughter. When the intestinal lining is lost, faecal material in the bottom of the coops will have a reddish-orange appearance to it, and the resulting intestine will be much weaker and more easily broken during evisceration.

Be careful during the unloading and hanging steps to minimise carcass bruising, broken legs, broken wings and red wing tips. If the doors (hinged front flap) to the coops (modules) are not positioned correctly during unloading, they will cause leg and wing damage. Bruising is minimal when coops are tilted in a smooth motion as opposed to bouncing the coop back and forth. Clean empty coops properly before reloading to minimise cross contamination among broilers. In the hanging area, use low levels of light to minimise the birds’ excitement once they are placed in the shackles. Blue or red light seems to be most effective at calming broilers.

Stunning, Slaughtering and Bleeding

Stunning of broilers is commonly done in the range of 12 to 150mA (milliamps) per bird of electrical current for a duration of two to 11 seconds. This practice is important, not only because it renders the bird unconscious, but also because it affects bleeding, feather release and overall meat quality. When the stunning voltage is high, wing haemorrhages, red skin condition, poor feather removal, broken bones and blood splashes in the meat may result.

The main concern with stunning, slaughtering and bleeding is to minimise the number of birds that are improperly bled and to limit those that have not expired before they enter the scalder. The position of the bird’s head during the slaughter operation is critical for proper bleeding and depends upon the alignment of the toe and head guide bars. If the bird’s head is not in the correct position for neck cutting, the trachea and oesophagus will also be severed. When the trachea and esophagus are severed, it is difficult to remove the head and lungs. The USDA recommends a bleed time in the range of 55 seconds to 2 minutes and 13 seconds.

Scalding and Defeathering

After bleeding, birds are scalded by immersion in a scald tank for 1.5 to 3.5 minutes, depending upon the water temperature. Scalding facilitates feather removal, but only if a uniform temperature is maintained throughout the scalder. When the scald temperature is too high, carcasses become discoloured due to uneven moisture loss. If the bird is alive when it enters the scald tank, the trachea, oesophagus, lungs, crop, gizzard and air sacs may become contaminated with scald water. The resulting carcass will be red in appearance. Moreover, the lungs may collapse and be difficult to remove, or they may drip as the viscera is transported through the plant.

Carcasses leave the scalder and go through a series of pickers designed to remove feathers from the body, wing, hock and neck. Feather removal is most successful when the pickers are placed close to the scalder so that the bird’s body temperature remains high during picking. The pickers can be a major source of carcass bruising, wing breakage and broken hocks, especially if rubber fingers are worn or not positioned correctly.

Eviscerating

During the evisceration process, carcasses can easily become contaminated with faecal material, especially if the vent opener and draw hand are misaligned or the intestines are unusually weak. If the body cavity of the bird appears convex, then the length of the feed withdrawal before processing was too short, and the bird’s intestines are full of faecal material.

Full intestines are more easily cut or torn during evisceration, and the contents may leak on to the carcass during extraction. On the other hand, when birds go without feed for too long before processing (greater than 14 hours), then the intestinal lining is lost and intestines may break during extraction. Carcass, gizzard and liver contamination with bile are also related to an extended feed withdrawal time. Contaminated surfaces on the carcass have to be washed, trimmed or vacuumed at a reprocessing station, and this process is expensive and time–consuming.

Chilling and Packaging

The chilling operation decreases the carcass temperature to 40°F within four hours of slaughter and inhibits microbial spoilage. Rapid chilling limits the growth of pathogenic bacteria on the carcass and increases the products’ shelf-life, especially when an appropriate amount of chlorine (20 to 50ppm) is used in the chiller water. Depending upon the extent of their attachment, bacteria present on the carcass as it enters the chiller are frequently removed during the chilling operation.

After chilling, carcasses are hung on a drip line generally for 2.5 to 4.0 minutes to control the amount of moisture pick-up. Although most of the moisture from chilling is retained in the skin, the amount of cutting during evisceration will have a significant effect on carcass water retention. Carcass temperature on exit from the chiller must be 40°F or less to comply with the USDA regulations.

In the packaging area, whole carcasses or parts must have an internal product temperature of 40°F or less. This temperatures should be maintained throughout storage and shipment. Also place emphasis on minimising recontamination of the product with proper equipment sanitation and good manufacturing practices.

Summary

Poultry is processed primarily to convert the birds’ muscles into meat, to remove the unwanted components of the bird (blood, feathers, viscera, feet and head), and to keep microbiological contamination at a minimum.

The ultimate quality of the final product depends not only on the condition of the birds when they arrive at the plant but also on how the bird is handled during processing. Bruising, broken bones, missing parts and high carcass reprocessing numbers can cause significant economic losses.

Unloading, stunning, slaughter, scalding, picking, eviscerating, chilling and packaging poultry are some of the processing steps that can result in product defects. Thus, these steps must be continuously monitored and precisely controlled.

References

Benoff, F.H., J.P. Hudspeth and G.A. Schuler. 1982. Troubleshooting guide for poultry processing. University of Georgia Extension Publication 40.

Bilgili, S.F. 1993. Broiler carcass quality: Seven-year survey. Broiler Industry 56:32-42.

Northcutt, J.K. and S. Savage. 1996. The broiler's last meal. Broiler Industry 59:24,26, 27.