Pigs are usually slaughtered after 4-7 months. Pigs intended for pork
are usually slaughtered 1-2 months younger than pigs for bacon. The pigs are transported with trucks that have compartiments with an individual capacity of 12-15 pigs. On arrival, they are unloaded and driven in lairage pens having a capacity equivalent to a truck compartiment. The pigs are held there for 24 hours to recover from fatigue and stress; and they are provided with enough water
to flush out intestinal pathogenic bacteria. Moreover, health inspections can be held during that holding period. The live animals are weighed prior to processing so that yield can be accurately determined.
Before slaughtering, pigs undergo electrical or carbon dioxide stunning. In the first case
, they are stunned using high frequency (50 Hz), low voltage electric current applied by means of two electrodes, which are placed on either side of the brine using tongs. The current induces a state of immediate epilepsy in the brain during which time the animal is unconscious. In the later case, the pigs are passed through a well with a CO2
atmosphere. Legally a minimum of a 70 % concentration of CO2
by volume is required, but a 90 % concentration is recommended. The pigs are again rendered unconscious due to the acidification of the cerebrospinal fluid upon inhalation of the CO2
. With the CO2
method “blood splashing” is eliminated, and it also removes the human element required in the electrical stunning.
During their state of unconsciousness, the pigs are hoisted onto an overhead rail for slaughtering.
Sticking & bleeding
In a state of surgical anesthesia, the pigs are shackled and hoisted for exsanguination. The stunned animals undergo exsanguination (sticking) with blood collected through a special floor
drain or collected in large funneled vats or barrels and sent to a rendering facility for further processing.
The carotid artery and jugular vein are cut to drain out blood and to get the muscles relaxed for easy dehairing. Pigs should be allowed to bleed for about 5 minutes.
Scalding & dehairing
Pig carcasses are not skinned after exsanguination. Instead, the carcasses are dropped into scalding water which loosens the hair for subsequent removal. The carcasses should be kept under water and continually moved and turned for uniform scalding. In large plants, carcasses enter the scalding tub and are carried through the tub by a conveyer moving at the proper speed to allow the proper scalding time. During the hard-hair season (September-November), the water temperature
should be 59° to 60°C and the immersion period 4 to 4,5 minutes, while in the easy-hair season (February-March), a temperature of 58°C for 4 minutes is preferable. In small plants without automation
, hair condition is checked periodically during the scalding period. The dehairing process is begun with a dehairing machine, which uses one or more cylinders with metal
tipped rubber beaters to scour the outside of the carcasses. Hot water (60°C) is sprayed on the carcasses as they pass through the dehairer moving toward the discharge end. The carcasses are removed from this machine, hand scraped, then hoisted again, hind quarters up. The carcasses are hand-scraped again from the top (hind quarters) down. Any remaining hairs can be removed by singeing with a propane or similar torch. Once the remaining hairs have been singed, the carcasses are scraped a final time and washed thoroughly from the hind feet to the head. Some plants pass the carcasses through a singeing through gas flames.
After scalding and dehairing, singeing, or skinning, the head is severed from the backbone at the atlas joint, and the cut is continued through the windpipe and esophagus. The head is inspected, the tongue is dropped, and the head is removed from the carcass. The head is cleaned, washed, and an inspection stamp is applied. Following heading, the carcass is eviscerated. The hams are separated, the sternum is split, the ventral side is opened down the entire length of the carcass, and the abdominal organs are removed. These viscera are received in a moving gut pan to segregate edible (heart, liver) and non edible offal. Intestines are cleaned for sausage
casings. The thoracic organs are then freed. Non edible offal is discarded into a barrel to be shipped to the rendering plant.
The carcass is cut into two halves. The meat
The carcass is then washed from the top down to remove any bone dust, blood, or bacterial contamination
. A mild salt
solution (0.1 M KCl) weakens bacterial attachment to the carcass and makes the bacteria more susceptible to the sanitization procedure, especially if the sanitizing solution is applied promptly. Dilute organic acids (2 percent lactic acid and 3 percent acetic acid) are good sanitizers. In large operations, carcass washing
is automated. As the carcass passes through booths on the slaughter line, the proper solutions are applied at the most effective pressure
Cutting and deboning are easier to carry out at lower temperature. Therefore, the carcasses are transferred to chill tunnels and chill rooms to cool them down to 0-1°C with air velocity typically 5 to 15 mph, equating to –5°C wind chill, for a 24-hour chill period. For thorough chilling
, the inside temperature of the ham should reach at least 3°C. With accelerated (hot) processing, the carcass may be held (tempered) at an intermediate temperature of 16°C for several hours, or be boned immediately. When large numbers of warm carcasses are handled, the chill room is normally precooled to a temperature several degrees below freezing
–3°C, bringing the wind chill to –9°C to compensate for the heat from the carcasses
Cutting into smaller pieces
The carcasses are processed into 3 cuts of meat (fore-end, middle and hind leg). During further cutting
into smaller pieces, the slaughters are assisted in their work by automated transport trays and conveyors. They help in cutting and sorting
meat and bone. The products are finally efficiently packaged and stored at low temperature prior to further processing.