The subject of hygiene has been covered, though diffusely, in almost every chapter of this Manual. Because of possible gaps and omissions, this chapter is presented to consolidate the subject and broaden its scope.
There are three basic criteria upon which hygienic measures in slaughterhouse organization and operations rest. These are the need to:
eliminate the risk of bacterial infection and food poisoning with meat as the vehicle of transmission;
prevent spoilage or putrefaction and thereby enhance the keeping quality and safety of meat;
secure meat of good eating quality, appearance and aesthetic value through proper handling. These latter criteria are discussed at length in Chapter 5.
Unless otherwise infected, the meat of freshly slaughtered animals is basically sterile. The presence of microorganisms on postslaughter carcasses is thus blamed on contamination occurring immediately before, during and after slaughter. The major sources of contamination are the animal itself, tools and equipment used in slaughter, the workmen and the condition of the slaughterhouse environment.
Dirt, soil, body discharges and excreta from animals in holding pens or lairages are the primary sources of contamination of carcasses in the later stages of the operation. This happens irrespective of whether or not the animals are fit and have passed antemortem inspection. In some establishments, the animals are washed just before stunning and bleeding. This step has the added effect of cooling or calming down the animals which factor is of importance in securing good quality carcasses.
For similar reasons, it is advisable to avoid operations on the floor. Hoisting during sticking, skinning, evisceration, washing and inspection is recommended in even modest premises, including makeshift ones. This, in effect, necessitates the provision of adequate floor space with suitable assembly of equipment to handle the animal bodies. In this respect it is advisable to have only a few workmen on the floor specialized or experienced in the various steps to handle the operations separately with quick and rapid dispatch. Where this is not possible or where floor space does not allow, the principle of separating dressing operations from offal cleaning ones must be strongly adhered to (Chapter 3).
The precautions that must be taken in slaughtering involve the following:
Sticking: the knife should be cleaned after each animal is disposed of and rinsed in hot water. It is said that a contaminated knife can transmit bacteria into the animal tissues during the early stages of bleeding when the pumping action of the heart is strongest. If this should happen, deterioration in deep tissues can also result.
Skinning: uncontrolled knife skinning or even fisting can similarly introduce spoilage organisms on the surface of the carcass. By the same token, singeing and scraping of the animal body as is practised under traditional African slaughters must be done to avoid splits in the skin by fire action; and after sponging and washing the carcass, clean hot water should be used in rinsing before evisceration.
Evisceration: care should be exercised not to puncture the intenstines. The workmen should follow the procedure of tying the bung (rectal end of the intestine) and the cut end of the oesphagus, then removing the paunch (intestine and stomach) first, followed by the pluck, (trachea, heart, lungs, etc.), both en masse and disposing of them separately. The pluck should be hung on a hook while the paunch should be dropped in a paunch container. Obviously the stomachs and intestines should not be opened while carcass dressing is in operation as such a move can easily cause contamination of the meat.
Washing: carcasses should be washed with clean potable water under pressure if possible. If water is a problem as happens in some rural areas, dry slaughter by trained men should be resorted to as it is safer for carcasses to be dry clean than to contaminate them with water from polluted sources.
Storage: this is dealt with fully in Chapter 7.
Offal handling: the various classes of edible offal, red, grey and dark (see Fig. 4 for definition), should be cleaned separately. The red offals can be washed on a separate line in the slaughter room after inspection, but grey offals (stomach and intestines) must be moved to a chamber provided for them. Initially they should be emptied of their contents dry, then flushed with water. The dark variety (head, feet) should be singed, scraped and washed outside the premises. Some dark and grey offals are utilized as byproducts by some communities, and should be disposed of as such rapidly.
Byproducts: delicate items such as glands and organs, if required, must be collected and conveyed from the plant by special methods as well as blood to be used for food or pharmaceutical purposes. Blood coagulates soon after it leaves the animal. Handling of this item as well as glands thus poses a problem hence unless the plant is a large one and previous arrangements have been made for their removal, collection should be avoided, more so in small rural premises.
Discards and waste: these are variable. Usually in developing countries they include the contents of the gut, blood and trimmings that cannot be used for food and therefore flushed into effluents. However, coagulated blood and other solids must be strained out before disposal. The subject is further dealt with in the next two chapters.
Personnel: next to the animal, equipment and methods of operation, the personal hygiene of the workmen is the most singularly important factor in slaughter operations, the reason being that contamination of food and disease transmission thereby depend equally on the human element as well as on the tools and methods of operation. Individuals assigned to slaughter services must be of sound health and of good personal habits. People who are sick or with boils and sores must be barred from the premises. All must be routinely examined for their health condition. Furthermore persons who habitually exhibit unhygienic habits like spitting, nose-blowing and coughing must not be employed. It is important to allow only approved and scheduled workmen into the premises at the time of operation and these individuals must be identified by a proper attire, e.g. a clean white T-shirt and trousers with long waterproof aprons over them. Boots must be worn with the trousers neatly tucked inside. Above all, the workers must be exposed to a formal code of hygiene.