Pig Carcass Processing Equipment: Scalding Tanks and Bristle Removal Machines

Pig carcass processing after bleeding follows a defined sequence: the carcasses are raised onto the bleeding rail, washed, freed of part of the flank and spinal bristle by hand or with electric clipping machines, and directed to scalding. Before scalding, the windpipe is plugged with a tampon. Scalding is carried out in vats at a water temperature of 62–65 °C for 3–5 minutes. The top layer of the skin — the epidermis — loosens, and the bristle bulb is released more easily from the hair follicle. During scalding, if the temperature is too high or the duration too long, the dermis proteins denature, the collagen sets, the bristle contracts, and during subsequent treatment it cannot be pulled out.

The K7–FSh2–K conveyorized scalding vat is used for scalding pig carcasses (Fig. 1). Carcasses are fed by a conveyor or an overhead rail, then along an inclined section onto a receiving table or directly into the scalding vat. As the carcasses are lowered into conveyorized scalding vats, they are placed in cradles with their heads facing one direction and submerged in the water using hold-down devices.

The conveyor moves the carcasses toward the scraping machine. In non-mechanized scalding vats, the carcasses are likewise positioned heads in one direction and pushed toward the scraping machine with a paddle, taking care that the carcass is washed by hot water on all sides. The water temperature in the scalding vat is maintained with thermoregulators. Completion of the process is judged by pulling bristle from the spine and head by hand: it should separate easily. Figure 1 — Diagram of the K7–FSh2–K conveyor scalding vat: 1 — tank; 2 — shower device; 3 — conveyor for transporting pig carcasses; 4 — cradle; 5 — device to prevent carcasses from floating up.

After scalding, the bristle is removed in scraping machines, where the carcasses are abundantly sprayed with water at 30–45 °C. The bristle is removed by a water jet or with special conveyors. The spent water is cleaned through filters, reheated, and fed back into the scraping machine. Carcasses cleaned in the scraping machines are delivered to the receiving table, where any remaining bristle is removed by hand, and then carried by an elevator onto the overhead rail for further processing.

Fine hair and down remain on the carcasses after the scraping machines. To remove these, the carcasses are sent for singeing, which is performed with burners or in singeing furnaces.

How does the FUShch–100 horizontal-transverse scraping machine work?

The FUShch–100 horizontal-transverse machine is a batch-action machine. It is part of a pig processing line that runs either without skin removal or with crupon removal, at a throughput of 100 head per hour. The FUShch–100 machine (Fig. 2) consists of a frame sheathed in sheet steel, on which two horizontal scraping drums are mounted; they rotate in the same direction but at different speeds.

The carcass turns as a result, which ensures effective cleaning. Steel stamped scrapers are fixed to the outer side surface of the drums (through plates made of elastic rubberized belt), with the row of scrapers of one drum set between the rows of the other. A polishing drum is mounted above the scraping drums. Figure 2 — FUShch–100 scraping machine: 1 — electric motor; 2 — frame; 3 — scraper; 4 — scraping drum; 5 — polishing drum; 6 — gearbox.

The scraping machine is driven by an electric motor through a gearbox and a system of chain transmissions. Loading pig carcasses into the machine from the scalding vat is done by a conveyor built into the vat, or by a special loading device in the case of a conveyorless vat. During operation, the carcass is continuously sprayed with warm water from a shower.

Unloading from the machine happens automatically when the polishing drum is raised. The loading and unloading operations are performed by a special lever. The K7–FO2–E furnace (Fig. 3) is intended for singeing pig carcasses with the skin on and with crupon removal. Singeing takes place while the carcasses move through the furnace at a temperature of 1000 °C in the singeing zone. The carcasses remain in the singeing zone for 15–20 seconds. Figure 3 — Diagram of the K7–FO2–E furnace: 1 — side shield; 2 — extraction hood; 3 — water line for cooling the overhead rail; 4 — overhead rail; 5 — carcass orientation device; 6 — burner device; 7 — control electrode.

When singeing pig carcasses with the crupon already removed, the furnace burner devices are switched off according to their position, and the flame height is regulated along the upper boundary of the crupon using swivel shields.

A properly singed carcass should have an even brown color over its entire surface, free of cracks and deep burns to the skin. After abundant wetting under a shower for 5–10 minutes, the carcasses are cleaned of the layer of burnt epidermis and bristle. Cleaning is done in polishing machines or by hand with scrapers or knives.

In polishing machines, which are similar in design to vertical scraping machines, the carcasses are sprayed with cold water. When cleaned by hand, they are washed with shower brushes.

What is the crupon method of processing pig carcasses?

Crupon processing is a combined method of treating pig carcasses in which the most valuable side and back parts of the skin — the crupon — are separated from the carcass and used in leather production. The skin remains on the rest of the carcass, and the bristle, fine hair, down, and epidermis are removed from it.

After washing, the carcass is submerged back-up in the scalding vat in the cradles mounted on the vat's conveyor. The depth of submersion is 15–20 cm above the line of the teats. The crupon itself is not scalded this way. The heads are scalded under a shower mounted along the full length of the vat, with water at 62–65 °C for 3–5 minutes.

The scalded bristle is removed on scraping machines. The carcass is unloaded from the machines onto a table for manual finishing. With a knife, an incision is made in the skin along the boundary of the scalded part of the carcass, isolating the crupon, and the neck part is opened up so that the skin can be gripped with a fixture or chain. The crupon is removed on the same installations used for full skin removal.

After crupon removal, the carcasses are singed on the chest and belly sides in singeing furnaces or with special devices, calculated so that the back part, from which the crupon has been removed, is not subjected to high temperature. The carcasses are then sent for further processing.