dk1792 ch11

11

Slaughtering and ProcessingEquipment

MARÍA DE LOURDES PÉREZ-CHABELA andISABEL GUERRERO LEGARRETA

Universidad Autónoma Metropolitana–Iztapalapa, Mexico City, Mexico

I. INTRODUCTION

II. PLANT LOCATION AND FACILITIES

III. ANTEMORTEM HANDLING

IV. STUNNINGA. Electric ShockB. Captive-Bolt or Pneumatic PistolC. Carbon Dioxide

V. LANDING

VI. STICKING

VII. BLEEDING

VIII. DRESSINGA. Beef DressingB. Sheep DressingC. Pig Dressing

IX. OFFAL HANDLING AND INSPECTIONA. Beef Offal HandlingB. Sheep Offal HandlingC. Pig Offal HandlingD. Inedible By-products

X. COOLERS

XI. CONCLUSIONS

ACKNOWLEDGMENTS

REFERENCES

Copyright © 2001 by Marcel Dekker, Inc. All Rights Reserved.

I. INTRODUCTION

Slaughtering—the first step in the transformation of muscle into edible meat—affects thequality and quantity of meat. Meat quality depends on postmorten biochemical changes,which relate to sanitation, as well as physicochemical and physical attributes (aroma, color,and texture among others). From the quantity point of view, carcass yield is related to pre-and postmortem handling.

II. PLANT LOCATION AND FACILITIES

Because of noise and odor generation, slaughtering plants must not be located near urbanareas. The U.S. Department of Agriculture (USDA, 1981) recommends that plants be lo-cated far from areas where objectionable odors or particles are generated, such as dumps orchemical plants. Slaughtering plants should also have accessibility; therefore, they shouldbe connected to streets or highways but separated from other plants or buildings.

Water supply must be in good quantity because washing is a continuous operationthroughout the plant (Fig. 1). Non-potable water is a hazard and must be avoided. Carcassesare washed after dressing, so any bacterial contamination in the water supply will be passedto the meat substrate (Murray and Madden, 1996).

Water disposal is equally important, because the wastewater contains grease, blood,hair, and tissue and bone particles. Slope in floors is required (no less than 10 cm for each6 m in working areas, and 15 to 20 cm for each 6 m in the coolers) to avoid accumulationof effluents (USDA, 1981). Federal or local legislation related to waste disposal variesamong countries or regions of the same country, but almost every country where a slaugh-tering plant is built has its own legislation.

256 Pérez-Chabela and Legarreta

Figure 1 Water pipelines and a water-cooled saw.


Ceilings should be no less than 3 m high or more in certain working areas, such asthose for evisceration and cleaning. They should be flat and smooth and free of unneces-sary structures (Libby, 1986).

Building materials for walls, floors, drains, ceilings, and equipment are also subjectto regulations. All these materials should provide easy cleaning. In general, these mate-rials comprise concrete, ceramic floor tile, floor-glazed brick, glazed tiles, smooth surfacePortland cement plaster, plastic, or Portland cement plaster for ceilings. Certain materi-als in particular are not acceptable, such as lead, porcelain, wood, leather, fabrics, or anymaterial that undergoes chemical reactions (Ockerman, 1980b). Square angles or jointswhere material can accumulate must be avoided. Floors must be of any nonslippery ma-terial.

The size of the killing room may vary according to plant capacity, but in any case itmust have enough space for animal handling and equipment operation, with walking areasaround operative sections. Adequate lighting is also necessary, either natural or artificial.In any case, 220 lux in the working areas is necessary, 540 lux in the inspection areas, and110 lux in the coolers. The U.S. Department of Agriculture describes lighting necessary foreach operation and lamp placement. All lamps must have a protective shield. Ceilings mustbe painted in white or a light color. Ventilation and refrigeration also must be controlled forcomfort as well as for reducing microbial growth. A maximum temperature of 10°C is nec-essary in all working areas.

Hand-washing facilities and drinking fountains should be located in the workingrooms (Fig. 2). These must be pedal operated (Figs. 3 and 4). Facilities for boot washingbefore walking into the working area must be supplied (Gracey, 1989).

Product transferred in the plant should not come in contact with the doorways; 1.50m doorways are necessary. There must be double-acting doors, constructed of rust-resistant

Slaughtering and Processing Equipment 257

Figure 2 Hand-washing facilities and a pedal-operated platform.


materials, with a transparent panel at eye level. All windows, doors, and other openingsmust have insect and rodent barriers such as screens or seals (USDA, 1981).

III. ANTEMORTEM HANDLING

Antemortem facilities include livestock pens, inspection facilities, and holding pens.Transportation conditions from the production area to the slaughtering plant deeply affectmeat quality, besides being part of humane animal handling. Handling, time, climatic con-ditions, and general health of the animals determine transportation losses. For example,weight losses in cattle can reach the proportions shown in Table 1.

Once animals are in the livestock pens, water must be provided. All parts of the pen,as well as runways and ramps, must be paved with concrete or brick and well drained. Thenumber of animals in each pen depends on animal size. For instance, cattle require 7.5 � 6


Figure 3 Cleaning a beef carcass from a pedal-operated platform.


m for 20 to 25 animals. Sheds must be provided to prevent excessive sun exposure. Goodlightning (54 lux) is necessary. Holding pens allow the animals to walk into the stunningarea without unnecessary stress. Grandin (1991) describes specific handling of animals inthe holding pens in depth.

IV. STUNNING

Once the animals are inspected premortem, they are taken through the holding pens to thestunning area. Except for specific ritual slaughtering (kosher and halal), animals must bestunned before bleeding. Use of a specific stunning method depends on factors such as an-imal species, breed, age, and production costs. There are three main stunning methods: cap-tive bolt or pneumatic pistols, electric shock, and carbon dioxide tunnels.


Figure 4 A pedal-operated platform and a pig scalding tank.

Table 1 Weight Losses DuringTransportation in Cattle

Transportation time Weight loss(hours) (%)

Up to 24 1.05 to 3.9124 to 36 3.45 to 5.4036 to 72 3.88 to 6.3772 or more 3.96 to 7.00

Source: Aldana, 1984.


A. Electric Shock

Electric shock stunning it is usually applied to pigs and sheep. It consists in applying elec-tricity through the animal’s brain, using two electrodes to induce an epileptic shock, orthrough the heart. If the electric shock goes through the brain, the animal is only stunned,and bleeding must be carried out within 30 seconds because the animal can recover con-sciousness. In such a case, the electrodes must be placed on each side of the head (Fig. 5).Intensity must be no less than 250 mA and 75 V during 10 seconds (Grandin, 1980). Theelectrodes are kept moist in a 20% saline solution to assure electricity conduction. If a pigis left unbled for 2 to 3 min it will recover, and in 5 min will be completely normal. If elec-tricity goes through the heart, the shock is irreversible and kills the animal by electrocution.

If electric shock is adequately applied, the animal will not feel any pain. Conversely,if amperage is not high enough, the animal may feel a painful shock. Most large process-ing plants use electric stunning through the heart, applying the electric current from the


Figure 5 Electric stunning.


head to the back of the animal. In this method the animal must be restrained in a confinedarea (Fig. 6). As electricity is used, the stunning area must be isolated and kept dry. Forsafety reasons the operator must wear rubber boots and stand on insulated ground.

B. Captive-Bolt or Pneumatic Pistol

Stunning with a captive bolt or pneumatic pistol can be applied in several species, althoughthe specific way of application varies slightly. In calves, swine, horses, and cattle (Bos tau-rus), the muzzle is applied to the forehead. In Cebu cattle (Bos indicus), in sheep and inplants industrializing the brains, it is applied in the back of the head. This is because of thethickness of the forehead in Bos indicus and sheep (De la Puente, 1996). Captive-bolt pis-tols eject a metallic cylinder through the animal’s skull and return to their original positionfor the next shot. Alternatively, pneumatic pistols impact the animal’s head without pene-


Figure 6 An electric stunning restraint pen.


tration. In both cases, the brain cortex is permanently damaged. Captive-bolt pistols areused when the slaughtering rate is less than 240 or more animals per hour, because rechargeis time consuming. Air pressure in pneumatic pistols may vary if there is a malfunction inthe air compressor. If air pressure is to high, harm to the operator’s hands, back, or arms ispossible. When this stunning method is used in pigs, the muzzle is applied just above theeye level, in the center of the forehead (Aldana, 1984). Animals are confined to a restraintarea where movements are limited for the operator’s safety, as well as to prevent animalself-injuries.

C. Carbon Dioxide

The stunning action of carbon dioxide is accomplished by blockade of the animal’s neuralterminals, therefore reducing the nervous impulses. Carbon dioxide concentrations of 65%to 70% during 45 seconds work most efficiently. Bleeding must be carried out within thenext 30 seconds (Velazco, 2000). If the gas concentration is lower, the animals are not ad-equately stunned. If it is too high, there is a tendency for stiffness, reflex muscular activity,and inadequate bleeding. If time of exposure is too long, skin congestion can occur and thecarcass can take a bluish hue after scalding. CO2 is heavier than air, so all devices operateon the basis of keeping the gas at low levels, making the animals descend to an area wheresuitable gas concentrations are fed, such as the oval tunnel (for slaughtering 120 to 240 an-imals per hour) or the Ferris wheel (Libby, 1986). The advantages of using CO2 are thatnontoxic residues are found in meat or of by-products, and the animal’s body is relaxed, fa-cilitating skinning and evisceration; it produces less noise than other stunning equipment;it requires fewer operators; and it does not promote muscle hemorrhages as is the case withother devices. The disadvantages of CO2 are that it is slower than other stunning methods,although at more constant rate, and initial investment is high (Gracey, 1989).

V. LANDING

Once the animal is stunned, it is landed in an area separated from the bleeding area (Fig. 7).This landing area must be at least 2 m wide (USDA, 1981) and is designed to prevent im-properly stunned animals from running away.

VI. STICKING

It is desirable to keep the animal alive, but stunned, in order to eliminate the blood. Thor-ough bleeding can be achieved when the heart and respiratory functions are still working.

After stunning, death occurs due to massive bleeding by sectioning the carotid ar-teries and the jugular vein with a sticking knife. Because blood is a vehicle for microbialdistribution throughout the animal body, organisms introduced during sticking can befound after a few hours in other parts of the carcass. Carcass temperature also affects mi-crobial proliferation (Roberts et al., 1980). For this reason, it is important to remove anydirt in the area where the sticking knife was introduced. Oversticking (i.e., puncturing thepleura) causes the blood to flow into the chest cavity, increasing the risk of microbialcontamination.

Sticking knives are 15 to 25 cm. The point of the knife is inserted about 2 cm in frontof the breastbone, and an incision is made toward the jaw, penetrating 12 to 15 cm and sec-tioning the carotid artery and jugular veins. In sheep, the sticking knife is inserted immedi-



ately below and behind the ear, severing the jugular vein. In beef, an incision is made justin front of the sternum, also cutting into the main blood vessels (De la Puente, 1996).

VII. BLEEDING

Bleeding, to a large extent, reduces microbial contamination. It also prevent formation of“blood-splash” due to pressure built within the muscles, which diminishes the meat’s ac-ceptability and represents a hygienic risk (Palumbo et al., 1996). Blood is also of eco-nomic importance as it can be transformed into meal for animal consumption or used inpharmaceutical applications. Usually, sticking is done while the animal is hung from itshind leg; in this position, better bleeding is achieved although pressure can built up insome organs.

Rails 4.8 m high above the floor should be used for beef bleeding; 3.3 m for pig,sheep, and calf; 2.74 m for goat (USDA, 1981). Bleeding is carried out in curbed-in areaswith enough space to prevent blood from splashing on stunned animals lying in dry areasor on carcasses being skinned. In beef, once the animal is hung on the bleeding rail, the car-cass is not lowered until the completion of the process. In pigs, the carcass is later loweredfor scalding and de-hairing.

VIII. DRESSING

Once the animal has been bled, the hide, or skin, and viscera are detached from the carcassand it is then trimmed. The head, feet, and tail are left attached to the pig carcass, whereashead and hide are removed from beef carcasses. Finally, the carcasses are washed withhigh-pressure spraying.


Figure 7 Beef restraint pen and landing area.


A. Beef Dressing

Dressing starts with dehiding: an incision is made in front of the brisket on the centerlineof the neck towards the head. The animal is then scalped, the horns chopped, and the headis skinned out. A cut is made across the larynx and the head is detached by cutting throughthe occipital joint. The front legs are cut, leaving the knucklebones on the carcass (Fig. 8);the hind legs are cut through the tendons.

An incision is made down the hide, removing it from the carcass with the use of asmall saw (Fig. 9). The abdominal cavity is opened by cutting behind the brisket; the liveris removed by cutting it from the diaphragm, which in turn is cut. The content of the chestcavity is removed and the aorta is trimmed. The body is then sawn, dividing the carcass intotwo sides (Fig. 10).


Figure 8 Beef de-hiding.


To prevent microbial contamination it is important to trim excessive tissue, the areawhere the sticking knife was introduced, and the spinal cord. The carcass is then washed byhigh-pressure spraying (19 kg/cm2) (Velazco, 2000) (Fig. 11). Head and hide are not in-cluded in the carcass weight. Dressing of beef is carried out in rails at least 3.3 m (USDA,1981).

B. Sheep Dressing

The sheep’s legs are cut from the knuckle down the front legs; the skin is removed, start-ing from the neck up to the root of the tail; and the hind legs are cut. Evisceration and wash-ing are similar to that described above. Head, skin, forefeet and hindfeet, and viscera shouldbe removed before weighing (Libby, 1986).


Figure 9 De-hiding saw.


C. Pig Dressing

After bleeding, pig carcasses are scalded in tanks with water at 60° to 65°C heated by steam(Fig. 12a). After 5 minutes the hair can be easily removed. The scalding vat should be con-structed of metal, and the floor must be well drained. The vats are equipped with a cradleto remove the pig after scalding and before scraping (Fig. 12b).

In de-hairing machines, the pig revolves and beaters remove the hair (Fig. 13a, b).De-hairing can also be carried out by hand (Aldana, 1984).

Carcasses are then hung from the hind legs in a shaving rail equipped with a drainedcabinet washer. The remaining hair is then burned off by using a blowtorch (Fig. 14) or bypassing the carcass through a furnace, allowing the skin to become dry and hard. Eviscer-ation is carried out in a similar way as with beef (Fig. 15).


Figure 10 Splitting a beef carcass.



Figure 11 Beef carcass high-pressure spraying.

Figure 12 Scalding a pig carcass.A



Figure 12 Continued.B

Figure 13 Revolving pig de-hairing equipment.A


BFigure 13 Continued.

Figure 14 Burning off the remaining hair.

269


The carcass is then washed by high-pressure spraying (Fig. 16). Pig, sheep, goat, andcalf dressing rails should allow the leg hooks from which the carcass is suspended to be2.25 m above the floor or inspector’s platform (USDA, 1981).

IX. OFFAL HANDLING AND INSPECTION

Viscera inspection may vary from country to country. However, all legislations require ex-amination of indicative organs providing information about the health of the animal. There-fore, identification of carcasses and their respective viscera is necessary. The movement ofthe viscera on the inspection table should be synchronized with the movement of the car-cass conveyor. If any indication of an unhealthy animal is detected in the viscera, the car-cass can be easily removed from the line.

Depending largely on tradition, certain viscera are used for human consumption orare considered inedible. This is the case with pigskin, brains, and genitalia. Commercial as-pects are also considered in directing viscera for uses other than human consumption, astheir use in the pharmaceutical and other industries generally gives added value to variousinternal organs.

A. Beef Offal Handling

Brains and tongue are removed from the head. The tongue is removed first, inspected, thor-oughly washed, scraped, and hung from the root end to preserve the shape. The head is split


Figure 15 Splitting a pig carcass.


and the brain removed and inspected. Other parts of the head, such as cheek meat and lips,are used in some countries for edible product manufacturing. Trachea, lungs, and heart areremoved and examined. Lungs and heart are used for edible purposes and must be thor-oughly examined, as sometimes food material from the stomach can be found in thebronchial tubes (Ockerman and Hansen, 1988). The liver must be carefully detached fromthe gall bladder, examined and cut across the thin end to allow blood to drain. Spleen, stom-achs, and sweetbread are removed, trimmed of adhering fat or excessive tissue from otherinternal structures, and placed in a cooling room. Intestines are used in the preparation oftripe; they are thoroughly cleaned and trimmed of adhering fat. The esophagus is carefullystripped from the outer muscles and dried before use (Gracey, 1989). Blood is used eitherfor edible purposes in several countries (black pudding in Scotland, moronga in Mexico,butifarra negra in Spain)—sheep or pig blood generally being preferred—or directed to an-imal feed production. When paunches are used for edible purposes, they should be emptiedon tables (USDA, 1981).

B. Sheep Offal Handling

In a similar way as beef, some sheep viscera are used mainly for edible purposes: brain,tongue, head meat, liver, heat, lungs, spleen, sweetbread, heart, and liver. They are handledas described for beef offal. Tripe from sheep stomach is used in several traditional Euro-pean sausages. Lamb kidneys are usually left attached to the carcass, but in mutton carcassthey are separated and sold apart (Ockeman and Hansen, 1988).


Figure 16 Pig carcass high-pressure spraying.


C. Pig Offal Handling

The offal to live animal ratio is less in pig than in beef or sheep because the skin, head, feet,and tail are taken into account for total carcass weight. Its simple stomach weighs less thanthe various stomachs of ruminants. As with beef, the trachea, lung, heart, liver, and esoph-agus are used for edible purposes; the stomach is used as a container of some products; feet,tail, and kidneys are generally detached from the carcass and sold separately (Ockeman andHansen, 1988). The head is separated from the carcass; the tongue, brains, and cheek meatare removed in the same way as in beef carcasses. The skin is used for gelatin production,but is also eaten, after frying, as a snack.

D. Inedible By-products

By-products such as viscera are aimed for industries other than the human food industry.Their use varies according to animal species and is influenced by cultural aspects. In gen-eral, inedible offals are used for pharmaceutical purposes; for animal feed formulation asmeat, bone, and blood meal; or for other industries, as in the case of hide and wool. Theseby-products are gallbladder, bones, and hooves from beef, sheep, and pigs; horns and feetfrom sheep and beef; wool and skin from sheep. Beef hide and hair from pigs are inedibleby-products. Scraps and condemned parts can also be used for meat meals.

A number of pharmaceutical products are obtained from slaughter by-products,mainly from the thymus and thyroid of beef, sheep, and pig; pig stomach lining; sheepprostate and intestine; beef and sheep pancreas and suprarenal glands; pig and beef ovariesand spleen; and beef pituitary and pineal glands, corpus luteum, parathyroid, and tested(Libby, 1986).

Inedible products and catch basins for grease recovery must be located to avoid con-tact with handling of edible products. Flow of inedible products must assure that they willnot come in contact with edible products (USDA, 1981).

X. COOLERS

The average temperature of a cooler must be between 2° and 6°C. A certain degree of“sweating” occurs when relative humidity is high (70% or more) (Ockerman, 1980a). Re-quired building material in coolers must be easy to clean; floors must have a slope to allowproper drain. Rails should be at least 3.3 m above the floor for halves of beef, 9 m for calvesand hogs, and 2.25 m for quarters of beef; goat and sheep carcasses should be suspended1.95 m to the hook. Carcasses must hung be 1 m from the walls and 0.60 m from the re-frigeration equipment, with a separation among carcasses of 0.30 m (USDA, 1981). Edibleorgans and offal should be placed in a separate cooler of the carcasses. Retained carcassesor parts should be located in a refrigerated separate compartment (Aldana, 1984).

XI. CONCLUSIONS

Slaughtering methods are based on obtaining the optimum quality and quantity of meat.Humane killing, in addition to its ethical implications, results in better-quality meat. Reg-ulations may vary from one country or region to another, but in all cases the objective is toassure sanitation for the food market and safety for the workers. Use of edible and inedibleby-products, although largely based on economic and cultural factors, is an important partof the investment return.



ACKNOWLEDGMENTS

The authors thank Dr. Marcelo Signorini, Universidad Nacional del Litoral, Argentina, forhis comments. All photographs are courtesy of the University of Guelph.

REFERENCES

Aldana, L.L. Tecnología de la carne y sus productos. Editorial Pueblo y Educación. Havana, Cuba,1984.

De la Puente, J. Personal communication, 1996.Gracey, J.E. Higiene de la carne. 8th edition. pp. 72–94. Interamericana-McGraw Hill. Madrid,

Spain, 1989.Grandin, T. Is your hog stunner insulated? Meat Process. February 1980. p. 69.Grandin, T. Guias recomendadas para el manejo de animales para empacadores de carne. American

Meat Institute. Washington, DC, 1991.Libby, J.A. Matanza Humanitaria. In: J.A. Libby (Ed.). Higiene de la carne. pp. 47–53. Editorial Con-

tinental, Mexico City, 1986.Murray, K.A., and R.H. Madden. Assessment of materials or microbiological sampling of carcasses.

42th Internat. Conf Meat Sci Tech pp. 197–198, 1996.Ockerman, H.W. Quality control of postmortem muscle tissue. Volume 2: Environmantel control.

The Ohio State University. Washington D.C., 1980a.Ockerman, H.W. Quality control of postmortem muscle tissue. Volume 4: Microbiology. The Ohio

State University. Washington D.C. 1980b.Ockerman, H.W., and C.L. Hansen. Animal by-product processing. Ellis Horwood Ltd., Chichester,

UK, 1988.Palumbo, S.A., B.S. Eblen, A.J. Miller, and J.G. Phillips. Comparison of techniques to evaluate the

bacteriological quality of pig carcass surfaces. 42th Internat Conf Meat Sci Tech pp. 195–196,1996.

Roberts, T.A., H.J.H. MacFie, and W.R. Hudson. The effect of incubation temperature and site ofsampling on assessment of the number of bacteria on red meat carcasses at commercial abattoirs.J Hyg Camb 85:371–380, 1980.

U.S. Department of Agriculture. 1981. U.S. Inspected meat and poultry packing plants. AgricultureHandbook 570. Washington, D.C.

Velazco, J. Problemas de calidad en el sacrificio de bovinos. Carne Tec. Mexico City. January/Febru-ary, pp. 18–21, 2000.



dk1792 ch11

Education

postmortem handling

inspection areas

sheep offal handling

pig offal handling

beef offal handling

certain working areas

inspection facilities

slaughtering plants