Guidelines for slaughtering, meat cutting and further processing (2024)

EQUIPMENT

Slaughtering equipment, particularly for smaller-scale operations, need notbe elaborate and expensive. The amount of equipment will depend on theslaughtering procedures employed. If possible, all equipment should bemade of stainless steel or plastic, be rust resistant and easily cleaned andsanitized. Equipment which does not get in contact with the meat (e.g.overhead rails, working platforms, knocking pen) is usually made ofgalvanized steel.

Basic equipment needed for the slaughtering operation:

• stunning gun, electrical head tongs or simple stunning equipment fordirect blow
• knives:
  sticking - 15 cm sharpened on both sides
  skinning - 15 cm curved
• a sharpening steel
• oil or water sharpening stone
• scabbard and belt for holding knives
• meat saw - hand or electric and cleaver
• block and tackle or chain hoist strong enough to hold the weight of theanimal to be slaughtered
• pritch, chocks or skinning rack (dressing cradle)
• a strong beam, tripod or track 2.4 to 3.4 m from floor
• spreader - gambrel or metal pipe
• several buckets
• working platforms
• scalding barrel or tank
• pot, barrel or system for boiling water
• bell scrapers
• solid scraping table or platform
• thermometer registering up to 70°C
• hog or hay hook
• torch or flame for singeing

The last seven items indicate additional equipment required when hogsare scalded and scraped rather than skinned.

Useful additional equipment:

• knocking pen
• bleeding hooks (for vertical bleeding)
• blood-catching trough
• wash trough (tripe)Sanitation of hands and tools:
• hand wash-basin
• implement sterilizers

Means should be available to clean thoroughly all equipment coming intocontact with carcasses or meat. Implement sterilizers are stainless-steelboxes holding hot (82°C) water, shaped to suit particular equipmentknives,cleavers, saws, etc. (Fig. 2). Knife sterilizers should be placed inpositions where every operator who uses a knife has immediate access.Handles as well as blades must be sterilized. Each operator should have atleast two knives etc., one to use while the other sterilizes (Figs 10 and 11).

Failure to sterilize all knives and equipment regularly will result in carcasscontamination. Bacteria will be transferred from the hide to the carcass andfrom carcass to carcass (Fig. 12).

TREATMENT OF LIVESTOCK BEFORE SLAUGHTERAND ITS IMPACT ON MEAT QUALITY

Stress in its many forms, e.g. deprivation of water or food, rough handling,exhaustion due to transporting over long distances, mixing of animalsreared separately resulting in fighting, is unacceptable from an animalwelfare viewpoint and should also be avoided because of its deleteriouseffects on meat quality. The most serious consequence of stress is deathwhich is not uncommon among pigs transported in poorly ventilated,overcrowded trucks in hot weather. From loading on the farm to the stunningpen animals must be treated kindly, and the lorries, lairages and equipmentfor livestock handling must be designed to facilitate humane treatment.Stress immediately prior to slaughter, such as fighting or rough handling inthe lairage, causes stored glycogen (sugar) to be released into thebloodstream. After slaughter this is broken down in the muscles producinglactic acid. This high level of acidity causes a partial breakdown of themuscle structure causing the meat to be pale, soft and exudative (PSE). Thiscondition is mostly found in pigs.

10. Plastic (right) handles aremore hygienic than wooden (left)for knives and other equipment.Note the excessively worn knife(third from left) which should bediscarded	12. Poor hygiene duringcarcass dressing causesthe spread of bacteriafrom the skin of thecarcass to knives and tooperators' hands
11. Knives andother equipmentshould be keptsharp and in goodrepair

Long-term stress before slaughter such as a prolonged period of fightingduring transport and/or lairage leads to exhaustion. The sugars are used upso that less is available to be broken down and less lactic acid is produced.

The reduced acidity leads to an abnormal muscle condition known asdark, firm and dry (DFD) in pigs or dark cutting in beef. The condition israrer in lamb. Such meat has a high pH (above 6.0) and spoils very quicklyas the low acidity favours rapid bacterial growth.

Handling animals during transport and lairage

An electric goad (Fig. 13) should be used rather than a stick or tail-twistingnot only to avoid stress but also to prevent carcass bruising. Grabbing sheepby the fleece also causes bruising (Fig. 14).

To avoid fighting, animals not reared together must not be mixed duringtransport and lairage. Load and unload using shallow stepped ramps toavoid stumbles. Trucks should be neither over- nor underloaded.Overloading causes stress and bruising due to crushing. Underloadingresults in animals being thrown around and falling more than necessary.Drivers should not corner at excessive speed and must accelerate anddecelerate gently.

The lairage should have small pens. Corridors must curve and not bendsharply so that stock can see a way forward. Stock must not be slaughteredin sight of other stock. Plenty of clean water must be available. The lairagemust be well lit and ventilated. Do not hold stock in lairage for more thana day. Only fit, healthy stock may be slaughtered for human consumption.

Fasting before slaughter reduces the volume of gut contents and hencebacteria and therefore reduces the risk of contamination of the carcassduring dressing. It is usually sufficient for the animals to receive their lastfeed on the day before slaughter. Stock should have a rest period after arrivalat the slaughterhouse. However, long periods in the lairage can lead to DFDif the animals are restless and fighting or mounting.

Animals should be as clean as possible at slaughter. Producers shouldwash their animals before leaving the farm. Trucks used for transport mustbe washed after each load and the lairage at the slaughterhouse should bekept clear of faecal matter and frequently washed (Figs 15 and 16).

STUNNING AND BLEEDING OF SLAUGHTER ANIMALS

Stunning prior to bleeding

Most countries have legislation requiring that animals are renderedunconscious (stunned) by a humane method prior to bleeding. Exceptionsare made for religions which require that ritual slaughter without priorstunning is practised, provided the slaughter method is humane. Stunningalso makes sticking (throat-slitting) less hazardous for the operator. Theanimal must be unconscious long enough for sticking to be carried out, andfor brain death to result from the lack of blood supply.

13. An electric goad delivers asmall electric current via twoelectrodes to encourageanimals to move. It avoidsstress and carcass damage	15. Trucks must be thoroughlywashed after each load
14. Unsightly bruising caused bystriking the animal with a stick.This not only causes loss ofproduct but is also inhumane
16. Pens will need washingafter emptying

Methods of stunning

Direct blow to skull using a club or poleaxe. The blow must be dealt withprecision and force, so that the skull is immediately smashed, causinginstantaneous unconsciousness. In cattle the aiming point is in the middleof the forehead in line with the ears, where the skull is thinnest. Horses havethinner skulls and are therefore easier to stun by this method. In sheep andgoats the brain is more easily reached from the back of the neck. Pigs havea well-developed frontal cavity so the blow should be aimed slightly abovethe eyes.

Slaughtering mask. A bolt held in the correct position by the mask isdriven into the animal's brain by a hammer blow. The device is usually fittedwith a spring which returns the bolt to its original position.

Free bullet fired from a pistol into the skull is effective but unsafe. Thismethod has been used on horses and cattle.

Captive-bolt pistols fitted with a blank cartridge are effective on cattle andsheep but not pigs whose skulls are thicker (Figs 17 and 18). After firing,the bolt returns to its original position in the pistol. The bolt may or may notbe designed to penetrate the skull. With penetrating types the brain becomescontaminated with hair, dirt and bone fragments. If brains are to be saved asedible tissue then the non-penetrating type with a mushroom-shaped headshould be used.

Electrical stunning. An electric current of high frequency but, in the caseof manually operated equipment, of relatively low voltage (60–80 V) ispassed through the brain of an animal for a few seconds to produceunconsciousness. If applied correctly a deep state of unconsciusness isinvariably achieved. Strict safety rules must be observed. Head tongs (Fig.19) are suitable for pigs and sheep but not for cattle. The electrodes carriedon the ends of the tongs must be accurately placed (Figs 20 and 21). Placeswhere the skull is thick must be avoided. Electrical contact is impeded byhair and caked mud. Water or brine will improve contact but the head mustnot be completely wet otherwise the current will have a short-circuit pathavoiding the brain. The electrodes must be applied with strong pressure.

	19. Head tongs are used to stun pigsand sheep electrically but are not suitable for cattle. The electrode on theend of each tong is ridged for better contact
17. Captive-bolt stunner suitable for cattle	20. The electrodes must be applied firmly to either side of the head so that the electrical current passes through the brain causingunconsciousness in a few seconds
	21. Head tongs are also suitable for stunning pigs
18. Aiming point for stunning cattle

Carbon dioxide stunning is used only in large pig abattoirs. Pigs areinduced into a chamber and exposed to a concentration of 85 percent CO₂for about 45 seconds. Although effective for anaesthetizing sheep, it isimpractical because of large amounts of CO₂ collecting in the wool andaffecting operators on the killing line.

Bleeding after stunning

The objectives of bleeding are to kill the animal with minimal damage to thecarcass and to remove quickly as much blood as possible as blood is an idealmedium for the growth of bacteria.

Sticking, severing the major arteries of the neck, should immediatelyfollow stunning. Care must be taken not to puncture the chest cavity or it willfill with blood.

22. Immediately following stunning the animal is hoisted by one leg and stuck. For sheep the stickingpoint is in the side of the neck, the gash cut severing all the major blood vessels in a single movement	23. The sticking point forpigs is in the centre of the neck just in front of the breastbone

Cattle. Insert the sticking knife carefully just above the breastbone at 45°pointed toward the head. Ensure that the carotid arteries and jugular veinsare severed in one movement.

Sheep. Draw the knife across the jugular furrow close to the head severingboth carotid arteries. Alternatively, the knife may be inserted through theside of the neck, though this requires more skill (Fig. 22).

Pigs. As for cattle but do not go in too far or a pocket of blood will collectat the shoulder (Fig.23). To reduce contamination by the scalding tank waterthe cut should be as small as possible.

Bleeding on a rail

The most hygienic system of bleeding and dressing is to shackle the animalimmediately after stunning, then hoist it on to a moving rail. The animal isstuck while being hoisted to minimize the delay after stunning. Bleedingcontinues until the blood flow is negligible when carcass dressing shouldbegin without further delay (Fig. 24)

Blood for human use must be collected with special equipment to avoidcontamination from the wound, the gullet of the knife. A hollow knifedirects blood away from the wound into a covered stainless-steel containerwithout touching the skin or hide. The knife may be connected to a hose toreduce the risk of contamination. The hose may even be connected to a pumpto speed the blood flow. Between 40 and 60 percent of the total bloodvolume will be removed though this will be reduced if sticking is delayed.To prevent coagulation, citric acid solution made up with one part citric acidto two parts water is added at a rate up to 0.2 percent of the blood volume.The main sources of contamination during sticking and bleeding include theknife, the wound and the food-pipe. The knief should be changed after eachoperation and returned to a sterilizer. Cutting the hide of sheep and cattle andopening out to make a clean entry for the sticking knife reducescontamination from the wound. If the food-pipe is pierced semi-digestedfood may be regurgitated contaminating the blood and neck wound.

Horizontal bleeding

Horizontal bleeding is claimed to give faster bleeding rates and a greaterrecovery of blood. This may be due to certain organs and blood vessels beingput under pressure when animals are hoisted, thus trapping blood andrestricting the flow. Bleeding on the floor is very unhygienic. The operationshould take place on a specially designed, easily cleaned stainless-steeltable which should be cleaned frequently. If blood is to be saved it must notcome in contact with the table before reaching the collecting vessel.

	24. After sticking, theanimal should be leftto bleed until theblood flow becomesnegligible	25. Scalding/dehairing tankwhich accommodates fourpigs: one awaitingimmersion, two immersedand one just completingimmersion. When the barsare rotated the pigs changeposition
		26. After immersionany remaining loosehairs are scrapedfrom the skin
27. Simple tank forcombined scalding/dehairing. The tank isfilled with water at60°C, a pig is loweredin, the lid is closedand the paddlesrotate, the rubber tipsloosening the hairs

Bleeding without stunning

The Jewish and Muslim religions forbid the consumption of meat whichwas killed by any method other than bleeding. Since it is difficult toguarantee that all animals will recover consciousness after being stunned byany particular method, stunning is not generally allowed. There areexceptions, however. Some communities do accept low-voltage electricalstunning.

Because animals are fully conscious at the time of sticking, ritualslaughter may be less humane than sticking after stunning. To reduce thesuffering operators must be highly skilled so that a successful gash cutsevering all the veins and arteries is made quickly at the first attempt.Different communities have different regulations as to the orientation of theanimal at sticking, some favouring a position lying on its side, othersinsisting it lie on its back. The animal should not be hoisted untilunconsciousness due to lack of blood supply to the brain is complete.

SCALDING AND DEHAIRING OF PIGS (USING SIMPLE EQUIPMENT)

Scalding in water at around 60°C for about six minutes loosens the hair inthe follicle. Too low a temperature and the hair will not be loosened and toohigh a temperature and the skin will be cooked and the hair difficult toremove. The simplest equipment consists of a tank into which the pig islowered by a hoist. The water is heated by oil, gas, electricity or an opensteam-pipe.

To check the effectiveness of the scald, rub the skin with the thumb to seeif hair comes away easily. Some machines have the thermostatic controls andtimers. To reduce contamination, scalding water should be changedfrequently, pigs should be as clean as possible at sticking, and bleedingshould be fully completed before immersion.

In large factories pigs are transported through scalding tanks with rotatingbars (Fig. 25) or through long scalding tanks stretching from the stickingpoint to the dehairing point in the time required for an effective scald.

Dehairing is done with a specially formed scraper (bell scraper or knife).If the scald is effective all the hair can be removed by this manual method(Fig. 26). Another simple method is to dip the pig in a bath containing a hotresin adhesive. The pig is removed from the bath and the resin allowed toset partially when it is peeled off pulling the hair with it from the root. Thisis less labour-intensive than scraping and produces a very clean skin. Afteruse the adhesive is melted again, strained to remove the hair and returnedto the tank.

Another method of removing dirt and hair in one operation is to skin thecarcass though this is only done when the skin is required for leather goods.

With the simple scalding tank, dehairing and scalding may be combinedin one operation. Inside the tank are rotating rubber-tipped paddles whichare started after closing the lid. As the hair is loosened by the scalding waterit is removed by the rubbing effect of the paddles against the skin (Fig. 27).

Singeing removes any remaining hairs, shrinks and sets the skin,decreases the number of adhering micro-organisms and leaves an attractiveclean appearance. It may be done with a hand-held gas torch (Fig. 28).Automated systems transport the pig into a furnace and leave it long enoughfor an effective singe.

After singeing, black deposits and singed hairs are scraped off (Fig. 29)and the carcass is thoroughly cleaned before evisceration begins.

SKINNING OF CATTLE AND SMALL RUMINANTS

Cattle

The outer side of the hide must never touch the skinned surface of thecarcass. Operators must not touch the skinned surface with the hand that wasin contact with the skin.

Combined horizontal/vertical methods

Head. After bleeding, while the animal is still hanging from the shacklingchain, the horns are removed and the head is skinned. The head is detachedby cutting through the neck muscles and the occipital joint. Hang the headon a hook (Fig. 30). Lower the carcass on its back into the dressing cradle.

Legs. Skin and remove the legs at the carpal (foreleg) and tarsal (hind leg)joints. The forelegs should not be skinned or removed before the carcass islowered on to the dressing cradle or the cut surfaces will be contaminated.The hooves may be left attached to the hide.

28. After scraping away loose hairs any remaining hairs can be singed and the skin set with ahand-held gas torch	30. The head is completely skinned and hung on a hook toawait inspection
	29. A special knife, the black scrape, is used to scrape off any singed hairsand black deposits

	32. In the combined horizontal/vertical dressing method the carcass is lowered on to a cradle, the legs, brisket andflanks are skinned, then the carcass is raised to the half-hoist position. Note that this ismuch less hygienic than verticaldressing on a rail
	33. Note the possible contamination of the carcass by the intestines and the hidedragging on the floor in the combined horizontal/vertical dressing method
31. Correct cutting lines for hide removal

Flaying. Cut the skin along the middle line from the sticking wound to thetail. Using long firm strokes and keeping the knife up to prevent knife cutson the carcass, skin the brisket and flanks, working backwards toward theround (Fig. 31). Skin udders without puncturing the glandular tissue andremove, leaving the supermammary glands intact and attached to thecarcass. At this point raise the carcass to the half-hoist position, theshoulders resting on the cradle and the rump at a good working height (Figs32 and 33).

Clear the skin carefully from around the vent (anus) avoiding puncturingit and cut the abdominal wall carefully around the rectum. Tie off with twineto seal it. Skin the tail avoiding contamination of the skinned surface withthe hide. Raise the carcass free of the floor and finish flaying.

Vertical methods

High-throughput plants have overhead rails which convey the carcass fromthe sticking point to the chills. Hide removal is carried out on the hangingcarcass (Figs 34, 35 and 36). The operations are as in the combinedhorizontal/vertical method, but as it is not possible to reach the hide fromground level more than one operator is needed. A single operator may workwith a hydraulic platform which is raised and lowered as required.

Automatic hide pullers are used in high-throughput slaughterhouses.Some types pull the hide down from the hind, others from the shouldersupwards toward the rump.

Automation of hide removal reduces contamination since there is lesshandling of the carcass and less use of knives. Moving overhead rails alsoimprove hygiene by reducing carcass contact with operators, equipmentsuch as dressing cradles and with each other since carcasses are evenlyspaced.

Small ruminants

Sheep fleeces can carry large volumes of dirt and faeces into theslaughterhouse. It is impossible to avoid contamination of sheep and lambcarcasses when the fleece is heavily soiled. The fleece or hair must nevertouch the skinned surface, neither must the operator touch the skinnedsurface with the hand that was in contact with the fleece.

34. The leg is freed from theskin and the hock cut off

35. Pneumatically operated rotating knives (flayers) speed the removal of the hide from the flanks	36. Flaying knives are used for the more intricate parts of hide removal

Combined horizontal/vertical method

The animal is turned on its back and cuts are made from the knuckles downthe forelegs. The neck, cheeks and shoulders are skinned. The throat isopened up and the gullet (food-pipe) is tied off (see Fig. 41). The skin on thehind legs is cut from the knuckles down to the tail root. The legs are skinnedand the sheep is hoisted by a gambrel inserted into the Achilles tendons. Arip is made down the midline and skinning proceeds over the flanks usingspecial knives or the fists (see Fig. 39). The pelt is then pulled down overthe backbone to the head. If the head is for human consumption it must beskinned or it will be contaminated with blood, dirt and hairs.

Moving cratch and rail system. The hanging carcass is lowered on to ahorizontal conveyor made up of a series of horizontal steel plates, bowedslightly and divided into sets large enough to cradle a single animal. Twooperators usually work together on each lamb performing the leggingoperations and opening the skin to the stage where it can be pulled off theback. When the gambrel is inserted into the hind legs it is hoisted on to adressing rail.

Vertical method

At sticking the animal is shackled by one hind-leg and left to bleed. Dressingcommences with the free leg which is skinned and the foot removed (Fig.37). A gambrel is inserted into this leg and hung on a runner on a dressingrail. The second leg is freed from the shackle, skinned and dressed, thenhooked on to the other end of the gambrel. The skin is opened down themidline and cleared from the rump.

A spreader frame (a bar U-shaped at each end) spreads the front legs tosimplify work on the neck, breast and flanks. The front toes are held in eachend of the frame which is then slung up on to a separate travelling hook. Theanimal is therefore suspended by all four legs belly uppermost (Figs 38 and39). Skinning continues as in the combined horizontal/vertical method. Toclear the shoulders and flanks, the forelegs are freed from the spreader andthe feet removed, the animal returning to a vertical position. The skin cannow be completely pulled off (Fig. 40), including the head if this is forconsumption, though this takes some work with the knife. In both methods,after fleece removal the vent and food-pipe are cleaned and tied off (Fig.41).

37. Fleece removal starts with skinning the free hind leg. Care must be taken toavoid the hide touching the skinned surface or the carcass will be contaminatedwith faecal matter
38. With forelegs in a spreader frame and hind legs in a gambrel, the sheep is suspended in ahorizontal position	40. After skinning the neck andbreast, the front legs are freed and skinning continues in the vertical position with the flanks and back
39. The fists can be used to clear the fleece from the breast
	41. After skinning the neck, the food-pipe is freed and tied off toprevent regurgitation of stomach contents

EVISCERATION

With all species care must be taken in all operations not to puncture theviscera (Fig. 42). All viscera must be identified with the carcass until theveterinary inspection has been passed. After inspection the viscera shouldbe chilled on racks etc. for better air circulation (Fig. 43).

Cattle

The brisket is sawn down the middle (Fig. 44). In the combined horizontal/vertical system this is done with the animal resting on the cradle. The carcassis then raised to the half-hoist position and when hide removal is completethe abdominal cavity is cut carefully along the middle line. The carcass isthen fully hoisted to hang clear of the floor so that the viscera fall out undertheir own weight (Fig. 45). They are separated into thoracic viscera, paunchand intestines for inspection and cleaning (Figs 46 and 47). If any of thestomachs or intestines are to be saved for human consumption, ties aremade at the oesophagus/stomach, stomach/duodenum boundaries, theoesophagus and rectum having been tied off during hide removal. Thisprevents cross-contamination between the paunch and the intestines.

Small ruminants

A small cut is made in the abdominal cavity wall just above the brisket, andthe fingers of the other hand are inserted to lift the body wall away from theviscera as the cut is continued to within about 5 cm of the cod fat or udder.

The omentum is withdrawn, the rectum (tied off) loosened, and the viscerafreed and taken out. The food-pipe (tied off) is pulled up through thediaphragm. The breastbone is split down the middle taking care not topuncture the thoracic organs which are then removed.

Pigs

Loosen and tie off the rectum. Cut along the middle line through the skin andbody wall from the crotch to the neck (Fig. 48). Cut through the pelvis andremove the bladder and sexual organs. In males the foreskin must not bepunctured as the contents are a serious source of contamination. All theseorgans are considered inedible.

42. When cutting through the abdomen wall, if the viscera are punctured their contents willseverely contaminate the carcass	43. A portable rack suitable for hanging offal for chilling

44. A mechanical sawspeeds the splitting ofthe brisket but caremust be taken not topuncture the viscera

45. After carefully cutting the abdominal wall along the midline the viscera fall out under theirown weight	46. A suitable receptacle should catch the viscera so that theyare not contaminated by contact with the floor

47. A portable cartsuitable for catchingcattle stomachs andintestines with aseparate tray for edibleoffal such as liver,heart and lungs

Remove the abdominal and thoracic viscera intact. Avoid contact with thefloor or standing platform.

The kidneys are usually removed after the carcass has been split down thebackbone. The head is usually left on until after chilling.

SPLITTING, WASHING AND DRESSING OF CARCASSES

Hygienic carcass splitting with simple equipment

Cattle

Work facing the back of the carcass. Split the carcass down the backbone(chine) with a saw or cleaver from the pelvis to the neck (Figs 49 and 50).Sawing gives a better result but bone dust must be removed (Fig. 51). If acleaver is used, it may be necessary to saw through the rump and loin in olderanimals.

The saw and cleaver should be sterilized in hot (82°C) water betweencarcasses. Power saws increase productivity.

48. The body wall is split downthe midline taking care not topuncture the viscera

49. Mechanical saw for splittingthe backbone (chine) of beefcarcasses	51. Carcasses should be spray-washedto remove visible staining, payingparticular attention to bone dust and theinternal surface, but without usingexcessive amounts of water
50. Hand-saws aremuch slower thanmechanical sawsthough they arepreferable to cleaverswhich splinter bones

Pigs

These are suspended and are split down the backbone as for cattle, but thehead is generally left intact (Fig. 94).

Sheep

Sheep and lamb carcasses are generally sold entire. If necessary they can besplit by saw or cleaver, but a saw will probably be necessary for olderanimals.

Carcass washing

The primary object of carcass washing is to remove visible soiling and bloodstains and to improve appearance after chilling (Fig. 51). Washing is nosubstitute for good hygienic practices during slaughter and dressing sinceit is likely to spread bacteria rather than reduce total numbers. Stains of gutcontents must be cut off. Wiping cloths must not be used.

Carcass spraying will remove visible dirt and blood stains. Water must beclean. Soiled carcasses should be sprayed immediately after dressing beforethe soiling material dries, thus minimizing the time for bacterial growth.Under factory conditions bacteria will double in number every 20 or 30minutes.

In addition to removing stains from the skinned surface, particularattention should be paid to the internal surface, the sticking wound and thepelvic region.

A wet surface favours bacterial growth so only the minimum amount ofwater should be used and chilling should start immediately. If the cooler iswell designed and operating efficiently the carcass surface will quickly dryout, inhibiting bacterial growth.

Bubbling of the subcutaneous fat is caused by spraying with water atexcessively high pressure, which may be due to the pressure in the systemor a result of holding the spray nozzle too close to the carcass.

Carcass dressing

The object of carcass dressing is to remove all damaged or contaminatedparts and to standardize the presentation of carcasses prior to weighing.Specifications will differ in detail for different authorities. Veterinaryinspection of carcasses and offal can only be carried out by qualifiedpersonnel. Where signs of disease or damage are found the entire carcass andoffal may be condemned and must not enter the food chain, but more oftenthe veterinarian will require that certain parts, for instance those whereabscesses are present, be removed and destroyed. Factory personnel mustnot remove any diseased parts until they have been seen by the inspectorotherwise they may mask a general condition which should result in thewhole carcass being condemned. Any instructions from the inspector toremove and destroy certain parts must be obeyed.

REFRIGERATION, HANDLING AND TRANSPORT OFCARCASSES AND MEAT

Refrigeration of carcasses

Carcasses should go into the cooler as soon as possible and should be as dryas possible. The object of refrigeration is to retard bacterial growth andextend the shelf-life. Chilling meat post-mortem from 40°C down to 0°Cand keeping it cold will give a shelf-life of up to three weeks, provided highstandards of hygiene were observed during slaughter and dressing.

Carcasses must be placed in the cooler immediately after weighing. Theymust hang on rails and never touch the floor (Fig. 52). After several hoursthe outside of a carcass will feel cool to the touch, but the importanttemperature is that deep inside the carcass. This must be measured with aprobe thermometer (not glass), and used as a guide to the efficiency of thecooling.

52. Sheep carcassesin the chill-room,hung on rails clear ofthe floor and spacedto allow aircirculation to speeddrying

The rate of cooling at the deepest point will vary according to many factorsincluding the efficiency of the cooler, the load, carcass size and fatness. Asa general guide a deep muscle temperature of 6–7° C should be achieved in28 to 36 hours for beef, 12 to 16 hours for pigs and 24 to 30 hours for sheepcarcasses. Failure to bring down the internal temperature quickly will resultin rapid multiplication of bacteria deep in the meat resulting in off-odoursand bone-taint.

High air speeds are needed for rapid cooling but these will lead toincreased weight losses due to evaporation unless the relative humidity(RH) is also high. However, if the air is near to saturation point (100 percentRH) then condensation will occur on the carcass surface, favouring mouldand bacteria growth. A compromise between the two problems seems to bean RH of about 90 percent with an air speed of about 0.5 m/second.Condensation will also occur if warm carcasses are put in a cooler partiallyfilled with cold carcasses.

The cooler should not be overloaded beyond the maximum load specifiedby the manufacturers and spaces should be left between carcasses for thecold air to circulate. Otherwise cooling will be inefficient and the carcasssurface will remain wet, favouring rapid bacterial growth forming slime (seebelow).

Once filled, a cooler should be closed and the door opened as little aspossible to avoid sudden rises in temperature. When emptied, it should bethoroughly washed before refilling. Personnel handling carcasses duringloading and unloading operations should follow the strictest rules regardingtheir personal hygiene and clothing and should handle carcasses as little aspossible.

Marketing of meat under refrigeration

Chilled meat must be kept cold until it is sold or cooked. If the cold chainis broken, condensation forms and microbes grow rapidly. The same rulesabout not overloading, leaving space for air circulation, opening doors aslittle as possible and observing the highest hygiene standards when handlingthe meat apply. An ideal storage temperature for fresh meat is just above itsfreezing point, which is about - 1°C (- 3°C for bacon because of the presenceof salt). The expected storage life given by the International Institute ofRefrigeration of various types of meat held at these temperatures is asfollows:

Under commercial conditions, meat temperatures are rarely kept at - 1°Cto 0°C, so actual storage times are less than expected. The times would alsobe reduced if RH were greater than 90 percent.

Meat should be placed in the refrigerator immediately following receipt.Any parts which show signs of mould growth or bacterial slime should betrimmed off and destroyed. Hands must be thoroughly washed afterhandling such trimmings and knives must be sterilized in boiling water. Therefrigerator should be thoroughly cleaned after finding such meat andshould also be cleaned on a regular basis.

Carcasses, quarters and large primals should not be cut into smallerportions before it is necessary as this will expose a greater surface area forbacteria to grow. Freshly cut surfaces are moist and provide a better mediumfor bacterial growth than the desiccated outer surfaces of cuts that have beenstored for some time.

An accurate thermometer should be placed in the refrigerator and checkedregularly. The temperature should remain within a narrow range (0° to+ 1°C).

Transport of meat

Vehicles for transporting meat and carcasses should be considered as anextension of the refrigerated storage. The object must be to maintain themeat temperature at or near 0°C. Meat should be chilled to 0°C beforeloading. Meat should hang on rails, not on the floor. If stockinettes are puton carcasses they must be clean. Meat trucks should not carry anything otherthan meat.

The refrigeration is usually produced by injecting liquid nitrogen orcarbon dioxide (CO₂) into the compartment or by blowing air over CO₂chunks (dry ice). The temperature in these vans can be set and controlled tominimize the temperature rise and to avoid condensation on the meat surface(Fig. 53).

Insulated vans without refrigeration may be refrigerated by adding dryice. While this is a reasonably good alternative to the refrigerated truck itdoes not allow the temperature to be controlled.

Uninsulated vans and open trucks should not be considered as suitabletransport for meat, particularly in hot climates. In addition to thetemperature abuse, condensation will occur when the meat goes back intorefrigeration, and in open trucks the meat is exposed to attack from insects.Loading and unloading should be done quickly. If there are any unavoidabledelays then dry-ice blocks should be placed in the partly filled van.

53. Insulated vans withrefrigeration units should beused for transporting meat

Carcass and meat handling and marketing without refrigeration

Where refrigeration is unavailable either owing to financial or technicalreasons (e.g. no power supply), the shelf-life of meat is reduced to days orhours, not weeks. Slaughter and dressing must be near the point of sale andit must be quick and clean. If carcasses and meat are kept in well-insulatedrooms, the temperature can be reduced with dry-ice blocks, if these areavailable. Since it is easier to chill boneless cuts rather than whole carcasses,hot-boning should be considered.

Stock must be handled carefully to avoid producing high-pH meat whichwill spoil more quickly. Rooms used for slaughter and handling meat mustbe clean and well ventilated, but out of direct sunlight, dust-free and verminfree(rodents and insects). Hot water (82°C) must be available to clean allequipment and surfaces and personnel must work very hygienically.Receive all blood into sealed containers and have separate skips on wheelsfor hooves, skins, green offal and trimmings.

54. Processing andpacking of offal mustbe done in a roomseparated from theslaughter hall or othermeat-handlingfacilities

Dressing on a vertical hoist will minimize contamination by floor orcradle contact. Let nothing drop on the floor, only into skips. Personalhygiene must be scrupulous. Any spills of gut contents on to the meat shouldbe cut off, but careful work will avoid this. The dressed carcass should behung on rails. If beef is quartered to facilitate handling, the cut surface is atrisk.

Red offal should be hung on hooks. Any offal processing must be in roomsaway from meat-handling facilities (Fig. 54). Intestines for humanconsumption must be thoroughly cleaned and washed.

Storage and transport without refrigeration

Meat should be put on sale within a day of slaughter. If it has to be held itshould be hung in a clean, well-lit hall with good ventilation. Insects,rodents and birds must be kept out, dust must not blow in. Trays of offalshould be on shelves, not on the floor. Barrows for wheeling carcasses andquarters are better than carrying on shoulders, as they can be cleanedfrequently. All staff must wear clean clothing and observe strict personalhygiene. Transport of non-refrigerated meat is very hazardous. If meat is tobe put in stockinettes and sacks these must be very clean. Meat should beon rails in the truck or wagon, and it is not advisable to carry it more thana day's journey before sale.