Chillin?chickens which method works best?

CHILLING is an important step in processing poultry carcasses before marketing of the birds, and there are different ways to do it. Agricultural Research Service scientists at the Richard B. Russell Research Center in Athens, Georgia, compared two chilling methods to determine which better suits processors' needs. Food technologist Julie Northcutt, formerly with the ARS Poultry Processing and Swine Physiology Research Unit at Athens, and food technologist Doug Smith, in the ARS Quality and Safety Assessment Research Unit at Athens, evaluated the two primary industry methods in terms of meat quality, food safety and water management.

More than one way to chill out

Carcass temperatures must be quickly lowered after poultry slaughter to prevent growth of bacterial pathogens that may cause food-borne illness when consumed. Immersion chilling is the predominant method now used in the United States, but some poultry processors are beginning to convert to dry-air chilling. In immersion chilling, carcasses are submerged in tanks of cold water or an ice-and-water mix. Dry-air chilling is achieved by blasting carcasses with cold air. Evaporative air chilling cools poultry down by a combination of cold-air blasts and water misting. The industry standard is to bring carcasses to 40˚F (4˚C) or less within 4 to 8 hours (depending on carcass weight) after slaughter to inhibit growth of pathogens and spoilage microorganisms. Both immersion chilling and air chilling met criteria for limiting bacterial pathogen growth on carcasses. But tender chicken is also very important to consumers.

Chewy or tender?

During commercial processing, whole carcasses are aged under refrigerated conditions to allow the muscle fibers to relax and become tender. After aging for a few hours, the carcasses may be cut into parts or deboned. Northcutt and colleagues compared tenderness of breast fillets removed from carcasses immediately after chilling (0 hours aging) to fillets aged on carcasses for 150 minutes or 24 hours after chilling. For air- and immersion-chilling methods, all breast fillets were considered tender or very tender after 24 hours of aging, but shorter aging times caused variations in tenderness. According to Smith, shorter aging times are of interest to the industry because plants have limited space to store carcasses after chilling, and the additional holding time is costly. Research showed that air chilling led to better quality of breast fillets and provided higher cooked-meat yields than immersion chilling. In the tests, immersion-chilled and air-chilled fillets were deboned immediately after chilling or after 150 minutes. The researchers found that 70% of the immersion-chilled fillets were slightly tough to tough, and 30% were tender to very tender. Of the air-chilled fillets, 44% were slightly tough to tough, and 56% were tender to very tender. "In addition to improving meat quality, air chilling provided higher cooked-meat yields than immersion chilling. Color and texture of skinless breast fillets were similar for both chilling methods," says Northcutt. The team believes that the lower cooked yield of the immersion-chilled fillets was the result of high moisture absorption during chilling, which was later cooked out of the product. The issue of aging only relates to poultry that is further processed. "Processors selling whole carcasses may not have a reason to make a switch to air chilling based on meat quality," says Northcutt. "Air chilling may, however, be a suitable alternative for deboning and other processing operations."

A matter of water

In the end, water may be the most important factor in deciding which chilling method may be most feasible in the future. The two principal poultry chilling methods vary markedly in their water use. Immersion chilling requires almNike Air Max 98