Air-chilled chickens may be less likely to be contaminated with disease-causing microbes and last longer on grocery-store shelves than broilers cooled in water, according to preliminary University of Nebraska research.

The findings laid groundwork for broader farm-to-table research on taking safer chicken to market.

"We're pinpointing the things that impact the safety of these birds throughout the process," said Food Scientist Mindy Brashears.

The research began at MBA Poultry of Tecumseh, Neb., which opened in 1998 as the only federally inspected air-chilled poultry plant in the United States. Eager for evidence to help it market its Smart Chicken line as a premium product, it welcomed NU's interest in comparing its air-chilling processing with the immersion chilling used at other U.S. plants.

Chilling is a critical step in poultry processing because it lowers the carcass temperature to inhibit bacterial growth. Air chilling, in which broilers are chilled individually on an assembly line with a draft of cold air, is widely used in Europe. In the United States, poultry processors chill broilers in tanks with cold water flow. It is thought that at least the risk of cross-contamination is greater with immersion chilling since the broilers come into contact with each other. Immersion chilling also leads to water retention in the broilers - significant in light of emerging USDA labeling regulations that would require poultry processors to specify how much water they contain.

The Institute of Agriculture and Natural Resources team, which includes Brashears, Food Scientist Shelly McKee and Veterinary Scientist Eva Wallner-Pendleton, compared 350 broilers processed at MBA and 350 from an undisclosed immersion-chilling plant. They found that both batches of birds had roughly similar counts of non-disease-causing bacteria and generic E. coli. However, the air-chilled broilers had a lower incidence of Salmonella and Campylobacter, bacteria that can cause food-borne illness. The air-chilled chickens also had significantly fewer psychrotrophs, bacteria that grow at refrigeration temperatures and cause spoilage.

"That means it probably does have a longer shelf life, but we'll have to research that further," Brashears said.

The research also indicated that Campylobacter organisms from farms producing chickens for MBA were not resistant to most of the antibiotics tested on them, while broilers from the immersion-chilling plant were resistant. Those findings, though very preliminary, are significant because occurrence of antibiotic-resistant Campylobacter is a major food safety concern. Campylobacter jejuni is the No. 1 cause of food-borne illness.

Further research was delayed this year by financial woes that led MBA to close in January and go through a bankruptcy sale in June. As this story was being written, plans were for the Tecumseh plant to reopen under new ownership in late summer and resume production of the Smart Chicken line.

"We still need to carefully monitor MBA's process," McKee said. "There may be other factors" affecting the findings.

For example, it's possible that the Tecumseh operation is cleaner than the plant to which it's been compared. Or perhaps the growers from whom it gets its chickens use different processes that contribute to the lower incidence of pathogens.

That's why it's important to see the findings as just a piece of the farm-to-table process, the IANR team says. Researchers are studying about five chicken farms over several growing seasons, starting with summer 2000. They will focus on the incidence of pathogens and microbial volume on the farms; that will give them a clearer picture of the contamination levels for the chickens before they reach the plant.

The result of the NU research may be new guidelines and recommendations for farms, plants and retail stores on handling broilers.

A $250,000 USDA grant helps fund this research.

– Daniel R. Moser

Food Scientists Mindy Brashears (left) and Shelly McKee collect rinse water from a broiler in their lab. The researchers have been studying the differences in pathogen contamination between broilers chilled in water, the traditional method used by U.S. poultry plants, and those chilled in air.

Mindy Brashears swabs a chicken to test for bacteria. In preliminary research, UNL scientists found that air-chilled chickens had a lower incidence of Salmonella and Campylobacter, bacteria that can cause food-borne illness.

University of Nebraska Veterinary Scientist Eva Wallner-Pendleton eyes pathogen samples in a petri dish. Preliminary NU research has shown that chickens chilled with air have a lower incidence of certain disease-causing organisms than those chilled by immersion in water. The research into poultry chilling is a piece of a farm-to-table project that aims to take safer chicken to market.