Water Spray – Hogs, Spray, Hot Water
Industry: Meat (NAICS 3116)
NAICS process:
311611 Animal (except poultry) Slaughtering
Process Brief: The hog carcass is sprayed with water to loosen the hair for removal
Energy source: Steam/Natural Gas
Energy Intensity: 200-400 Btu/lb
Water spray scalding has replaced immersion scalding at some facilities, although steam spraying is more common at larger facilities. Water spraying helps to reduce hot water consumption and reduces contamination. Water spray systems use a conveyor to move the carcasses through a chamber where the carcasses are sprayed with hot water. Water drains from the carcass and is not recycled. Avoiding immersion helps to reduce contamination between different parts of the carcass and cross-contamination between carcasses is eliminated.
Steam scalding is replacing water immersion scalding in modern facilities where higher throughput and improved product safety are desired. Steam spray systems allow the hung carcasses to be scalded in a continuous process using saturated steam that is faster and more energy efficient than water immersion. One system claims to use only 1.5 liters of water (as saturated steam) per carcass and can process 40-120 hogs per hour in its automated process. The steam spray system uses multiple spray nozzles positioned in a steam cabinet through which the carcasses are conveyed. The steam condenses on contact, achieving an efficient transfer of thermal energy to the skin and loosening the hairs. Water drains from the carcass and is not recycled. Avoiding immersion helps to reduce contamination between different parts of the carcass and cross-contamination between carcasses is eliminated.
Water Immersion
Most hogs are dehaired by exposing the hide to steam or hot water, causing the hairs to become loose. A second process using brushes or rubber paddles actually remove the hair. Important considerations are product quality and avoiding contamination. Water immersion was the standard scalding technique but newer facilities use steam scalding. Water immersion is performed as a batch process in a tank that is large enough to handle one to three carcasses at a time. Steam is injected to maintain the desired temperature and most of the water is recycled between cycles. Generally, the tank is drained and cleaned every shift.
Hog carcasses are immersed in the tank that is filled with water at 136 to 140°F. The carcasses will be turned to ensure even scalding during the 4-4½ minute cycle. The water temperature is critical, because high temperatures degrade the meat and can excessively soften the skin, which can lead to tissue damage from subsequent handling. Low temperatures lead to excessive immersion times or difficult hair removal. The overhead conveyer immerses the carcass in the tank or the carcass may be dumped into the tank and removed by a crane. While scalding is necessary for hair removal, water immersion may spread contamination from hog to hog.
Dehiding
Most hog producers use a combination of scalding and dehairing to prepare a hog for evisceration. Dehiding is an alternative that eliminates these steps by removing the skin of the hog.
Energy Efficiency
Meat Processing – Carcass Cleaning
More Information
Carcass Cleaning – Steam Vacuuming
EPA http://www.epa.gov/ttn/chief/ap42/ch09/final/c9s05-1.pdf Open as PDF 
Source: Overview GRI-03/0075; Overview photo from http://www.mps-group.nl/en/red_meat_slaughtering/pig_slaughtering/ 3/2007; KOCH carcass scalder from http://www.kochequipment.com/site/equipment/product_info.php?id_product=211&id_industry=1&id_category=162