USDA Survey Shows Processing Improves Microbiological Profile of Chickens

WASHINGTON — Nov. 16, 2009 — Poultry processing, including immersion in cold water and the use of antimicrobial interventions, greatly improves the microbiological profile of raw chickens, sharply reducing the presence of Salmonella and other microorganisms, according to a large-scale survey by the U.S. Department of Agriculture.

“We observed a substantial reduction in the number of samples positive for Salmonella . . . and Campylobacter, suggesting that the anti-microbial interventions had an effect,” USDA scientists wrote in their report on a nationwide data collection program.

Only five percent of the raw chickens in the survey had Salmonella after chilling, and only 11 percent had Campylobacter, the survey showed, down from 41 percent and 71 percent, respectively, before evisceration. The actual number of bacteria on each raw chicken was also greatly reduced, by about 99 percent on average with respect to Campylobacter and 66 percent on average for Salmonella, the survey data show.

“The USDA survey shows that the industry is doing an excellent job of reducing the presence of potentially disease-causing bacteria on raw chicken,” said Steve Pretanik, director of science and technology for the National Chicken Council. “The investments made by the industry in improved technology and bacteria-fighting interventions have paid off in terms of a safer product for consumers.” He added that bacteria remaining on the raw product are destroyed by the heat of normal cooking.

The survey was conducted by USDA from July 2007 to June 2008 at 182 broiler slaughter plants. A total of 6,550 samples were collected, divided equally between samples taken at the rehang station (before evisceration) and after the chiller. As raw chickens went through processing, they encountered the antimicrobial measures in use in those plants, which typically include the use of chlorinated water in processing and in the chiller. The chiller itself uses ice-cold water to reduce the temperature of the eviscerated chicken to no more than 40 degrees Fahrenheit in order to prevent the growth of most organisms.

After the chiller, the vast majority of chickens had very few Salmonella or Campylobacter cells on them, according to standard measurements of microbial presence. Some 97 percent of chickens had three or fewer Salmonella cells per milliliter of rinse solution, the data show, and 99 percent had 100 colony-forming units of Campylobacter or fewer per milliliter of rinse solution. These are considered very low levels, Pretanik said.

“The tests are very sensitive and detect very low levels of bacteria,” Pretanik said. “A processed raw chicken can have extremely low levels of these organisms present and still be counted as a positive sample.”

Results of the survey were published by the Office of Public Health Science in the USDA’s Food Safety and Inspection Service.

The National Chicken Council represents integrated chicken producer-processors, the companies that produce and process chickens. Member companies of NCC account for approximately 95 percent of the chicken sold in the United States.


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