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United States Department of Agriculture

Agricultural Research Service

Title: The Presence of Empty Feather Follicles on Processed Carcasses Does Not Alter Carcass Bacteria Levels

Author
item Buhr, Richard

Submitted to: Feedinfo News
Publication Type: Trade Journal
Publication Acceptance Date: March 28, 2005
Publication Date: April 1, 2005
Citation: Buhr, R.J. The presence of empty feather follicles on processed carcasses does not alter carcass bacteria levels. Feedinfo News. p. 254697.

Interpretive Summary: The prevention and removal of bacterial food borne human pathogens from poultry carcasses is a constant challenge for both poultry processors and researchers. The application of carcass rinses prior to chilling are intended to physically remove bacteria, kill bacteria, or inactivate bacteria and prevent their growth and proliferation. Most chemical disinfectants require direct contact with the bacteria cell to be fully effective. In applying chemicals to carcasses, the method of application must overcome carcass anatomy (internal and external surfaces), surface water tension, biofilms, and any organic matter that may inactivate chemicals. Chemical solutions have been applied using dips, washes, high pressure sprays, under vacuum, and at very small particle size in mists or fogs. Methods for obtaining chemical penetration into empty feather follicles has been considered a challenge. The empty feather follicles on defeathered poultry carcasses are commonly speculated to harbor bacteria during and after processing (National Advisory Committee on Microbiological Criteria for Food, 1997). Numerous publications plainly state that bacteria become lodged in feather follicles during processing, and that the feather follicle shrink during chilling and trap bacteria within, but very few of these publications provide data to support these statements. Readers have repeated the statement that feather follicles on poultry carcasses harbor bacteria, thereby perpetuating the distribution of this undocumented assumption. Our recent experiments were designed to evaluate the relative importance of empty feather follicles on the total carcass bacterial level following chilling, the point at which poultry would be first available to the consumer. The presence of bacterial pathogens in feather follicles during and after processing has not been demonstrated for carcasses colonized with natural levels of these pathogens (Buhr et al., 2003). However, Salmonella have been photographed within empty feather follicles after soaking defeathered skin pieces for 2 hours in a highly concentrated suspension of Salmonella (Kim et al., 1996). Locating naturally occurring salmonellae within an empty feather follicle during or immediately after processing has not been reported. The risk to public health (through cross-contamination of other foods) is considered greater for those bacteria that are easily removed from a carcass than for those bacteria that are either present “inside the carcass” or firmly attached to the carcass, since attached bacteria would be killed during cooking (van Schothorst et al., 1976). To study the relative importance of feather follicles in harboring bacteria we proposed developing featherless broilers, which would not have feather follicles, and processing them with feathered broilers for comparison. Fertile eggs from a genetic line of featherless chickens (scaleless) were obtained from The University of California-Davis and hatched at the USDA-ARS Russell Research Center in Athens, Georgia. By the use of artificial insemination, these small-framed featherless roosters were crossbred to commercial broiler breeder hens to obtain heterozygous (Sc / sc) feathered chicks. After two additional crosses with broiler breeder stocks, the current flock is mated interse and produces chicks in a ratio of ¾ feathered and ¼ featherless. The feathered and featherless offspring currently obtain a body weight of more than 2 kg at six-week-of age. Comparable body weights from hatch through processing, enables similar physical contact with equipment and pressures on the carcasses during processing. To evaluate the importance of feather follicles, these genetically feathered and featherless sibling broilers were hatched, raised, challenged with bacteria, subjected to feed withdrawal, transported, processed, and immersion chilled togethe

Technical Abstract: The prevention and removal of bacterial food borne human pathogens from poultry carcasses is a constant challenge for both poultry processors and researchers. The application of carcass rinses prior to chilling are intended to physically remove bacteria, kill bacteria, or inactivate bacteria and prevent their growth and proliferation. Most chemical disinfectants require direct contact with the bacteria cell to be fully effective. In applying chemicals to carcasses, the method of application must overcome carcass anatomy (internal and external surfaces), surface water tension, biofilms, and any organic matter that may inactivate chemicals. Chemical solutions have been applied using dips, washes, high pressure sprays, under vacuum, and at very small particle size in mists or fogs. Methods for obtaining chemical penetration into empty feather follicles has been considered a challenge. The empty feather follicles on defeathered poultry carcasses are commonly speculated to harbor bacteria during and after processing (National Advisory Committee on Microbiological Criteria for Food, 1997). Numerous publications plainly state that bacteria become lodged in feather follicles during processing, and that the feather follicle shrink during chilling and trap bacteria within, but very few of these publications provide data to support these statements. Readers have repeated the statement that feather follicles on poultry carcasses harbor bacteria, thereby perpetuating the distribution of this undocumented assumption. Our recent experiments were designed to evaluate the relative importance of empty feather follicles on the total carcass bacterial level following chilling, the point at which poultry would be first available to the consumer. The presence of bacterial pathogens in feather follicles during and after processing has not been demonstrated for carcasses colonized with natural levels of these pathogens (Buhr et al., 2003). However, Salmonella have been photographed within empty feather follicles after soaking defeathered skin pieces for 2 hours in a highly concentrated suspension of Salmonella (Kim et al., 1996). Locating naturally occurring salmonellae within an empty feather follicle during or immediately after processing has not been reported. The risk to public health (through cross-contamination of other foods) is considered greater for those bacteria that are easily removed from a carcass than for those bacteria that are either present “inside the carcass” or firmly attached to the carcass, since attached bacteria would be killed during cooking (van Schothorst et al., 1976). To study the relative importance of feather follicles in harboring bacteria we proposed developing featherless broilers, which would not have feather follicles, and processing them with feathered broilers for comparison. Fertile eggs from a genetic line of featherless chickens (scaleless) were obtained from The University of California-Davis and hatched at the USDA-ARS Russell Research Center in Athens, Georgia. By the use of artificial insemination, these small-framed featherless roosters were crossbred to commercial broiler breeder hens to obtain heterozygous (Sc / sc) feathered chicks. After two additional crosses with broiler breeder stocks, the current flock is mated interse and produces chicks in a ratio of ¾ feathered and ¼ featherless. The feathered and featherless offspring currently obtain a body weight of more than 2 kg at six-week-of age. Comparable body weights from hatch through processing, enables similar physical contact with equipment and pressures on the carcasses during processing. To evaluate the importance of feather follicles, these genetically feathered and featherless sibling broilers were hatched, raised, challenged with bacteria, subjected to feed withdrawal, transported, processed, and immersion chilled together. The levels of carcass bacteria (salmonellae, Campylobacter, Escherichia coli, coliforms, and total aerobic bacteria) were determine after chilling by subjecting each carcass to a whole carcass rinse. Results from our experiments on eight separate days of processing revealed that the presence of feathers and feather follicles did not appear to markedly influence the recovery of the human food borne pathogens salmonellae or Campylobacter from broiler carcasses sampled after immersion chilling. However, featherless carcasses had slightly higher counts of E. coli, coliforms, and total aerobic bacteria. Apparently, feathers although contaminated with bacteria during production and transport result in lower carcass bacterial levels following defeathering and chilling in spite of containing more than 5,000 empty feather follicles. These results differ slightly from our previously reported results, that found no detectable differences between feathered and featherless carcass breast skin (Buhr et al., 2003) or whole carcass rinses (Cason et al., 2004) when sampling occurred immediately after defeathering. The absence of a difference following defeathering in the previous experiments may have been due to the addition of cloacal contents expelled from the carcasses during defeathering leading to elevated numbers of bacteria on all the carcasses. When samples were collected following immersion chilling, most loose bacteria would have been removed from the carcass during rinsing and chilling, therefore providing the ability to detect small differences in bacteria levels between feathered and featherless carcasses. The presence of feathers and empty feather follicles on processed carcasses after immersion chilling appears to have minimal influence on the level of recovery of E. coli, coliforms, and total aerobic bacteria, and no detectable influence on the recovery levels of salmonellae or Campylobacter. These experiments provide additional data that contradicts the assumption that empty feather follicles are a significant harbor for carcass bacteria on processed poultry carcasses. If empty feathers follicles on a carcass do indeed contain bacteria following immersion chilling, it does not appear that the number of these bacteria is great enough to impact the overall bacterial level of the entire carcass as determined in carcass rinses. References: Buhr, R. J., M. E. Berrang, and J. A. Cason. 2003. Bacterial recovery from breast skin of genetically feathered and featherless broiler carcasses immediately following scalding and picking. Poult. Sci. 82:1641-1647. Cason, J. A., A. Hinton, Jr., R. J. Buhr. 2004. Impact of feathers and feather follicles on broiler carcass bacteria. Poult. Sci. 83:1452-1455. Kim, K. Y., J. F. Frank, and S. E. Craven. 1996. Three-dimensional visualization of salmonella attachment of poultry skin using confocal scanning laser microscopy. Lett. Appl. Microbiol. 22:280-282. National Advisory Committee on Microbiological Criteria for Foods. 1997. Generic HACCP Application in Broiler Slaughter and Processing. J. Food Prot. 60:579-604. University of California-Davis. Genetic Resources Conservation Program, University of California, One Shield’s Ave., Davis, CA, 95616, Contact Jacqueline M. Pisenti at 530-754-8508, e-mail jmpisenti@ucdavis.edu. van Schothorst, M., M. D. Northold, E. H. Kampelmacher, and S. Notermans. 1976. Studies on the estimation of the hygenic conditions of frozen broiler chickens. J. Hyg. 76:57-63.

Last Modified: 8/27/2014
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