The evaluation of combined chemical and physical treatments on the reduction of resident microorganisms and Salmonella Typhimurium attached to chicken skin

Abstract

This study was conducted to evaluate the efficacy of sodium hypochlorite (NaOCl, 0-200 mg/kg), thiamine dilauryl sulfate (TDS, 1,000 mg/kg), and ultrasound (37 kHz, 380 W) on reducing Salmonella Typhimurim, mesophilic aerobic bacteria (MAB), and coliforms on chicken skin. Chemical and physical treatments were applied for 5 min either singly or jointly, and Salmonella previously inoculated on chicken skin were quantitatively assessed using brilliant green agar, and the populations of MAB and coliforms in the native flora were enumerated using plate count agar and violet red bile agar, respectively. In the evaluation of bacterial attachment/detachment, chicken skin was quantitatively assessed for loosely, intermediately, and tightly attached bacteria. The treatment effects on bacteria detachment were also visualized using field emission scanning electron microscopy. In addition, color and textural properties of the skin after treatments were evaluated using a color difference meter and texture analyzer. Antimicrobial activity of NaOCl increased as the NaOCl concentration was increased, especially for loosely attached cells. The combination of 200 mg/kg NaOCl and ultrasound (NaOCl/ultrasound) significant reduced loosely, intermediately, and tightly attached bacteria populations by 0.75 to 0.47, 0.43 to 0.41, and 0.83 to 0.54 log cfu/g for MAB, coliforms, and Salmonella Typhimurium, respectively. However, the combination of NaOCl and TDS (NaOCl/TDS) did not sufficiently reduce those cells on chicken skins, except for loosely attached MAB and coliforms. The NaOCl/ultrasound combination produced a higher reduction in numbers of inoculated and native bacteria flora than any single application, with no negative effect on skin color or texture. Generally, the loosely attached bacteria were less resistant to the chemical and physical treatments than the intermediately and tightly attached bacteria in chicken skin, presumably due to their location in deeper skin layer and crevices. Further research is needed to investigate how the intermediately and tightly attached microorganisms can be effectively eliminated from chicken skin.

Enhancement of bactericidal effects of sodium hypochlorite in chiller water with food additive grade calcium hydroxide

“…Although chicken is chemically sanitized during processing and subsequently cleaned before packaging, some microorganisms cannot be removed completely, especially bacteria strongly attached to chicken skin [5, 14, 23, 30]. This is because these microorganisms, including Salmonella and Campylobacter, are able to become entrapped in deep skin layers, crevices, or feather follicles, thus becoming protected from chemical agents [5, 15, 29]. …”

Salmonella Harborage Sites in Infected Poultry That May Contribute to Contamination of Ground Meat

“…Immunohistochemistry was effective for identifying specific sites of Salmonella localization and in chicken and turkey skin, Salmonella cells were organized in clusters on the epidermal keratin and were occasionally present in the lumen of feather follicles. Studies of skin that was inoculated with Salmonella have reported bacterial cells present on the flat areas and ridges of the skin, and entrapped in feather follicles (Kim et al, 1996;Lee et al, 2014). This study is the first that describes Salmonella cells within the lumen of feather follicles of colonized poultry.…”

“…Unfortunately, Salmonella cells lodged in crevices and within feather follicles are protected from rinses and chemical treatments (Lillard, 1989;Kim et al, 1996;Lee et al, 2014). Similar observations have been made if combination of sonification and chemical treatments is used on poultry carcasses (Lillard, 1993;Lee et al, 2014). Entrapped Salmonella cells can be released once skin is ground and this may contribute to contamination of ground poultry when ground skin is mixed with other ground components.…”

“…USDA-approved chemicals for the processing plant can reduce Salmonella loads in scalding and chilling baths, but they are not as efficient in eliminating Salmonella entrapped into the skin (Lillard, 1989;Yang et al, 2001;Lee et al, 2014). Unfortunately, Salmonella cells lodged in crevices and within feather follicles are protected from rinses and chemical treatments (Lillard, 1989;Kim et al, 1996;Lee et al, 2014).…”

Food Grade Pimenta Leaf Essential Oil Reduces the Attachment of Salmonella enterica Heidelberg (2011 Ground Turkey Outbreak Isolate) on to Turkey Skin

“…Heidelberg controls. Sample preparation for electron microscopy was conducted as previously described with some modifications ( Lee et al, 2014 ). Briefly, immediately after each treatment, the skin samples were stored in primary fixative [3% paraformaldehyde, 1.5% glutaraldehyde, and 2.5% sucrose in 0.1 M sodium cacodylate buffer with 5mM calcium chloride and 5mM magnesium chloride (pH 7.4)] for 12 h. Then the samples were fixed in 2% osmium tetroxide and 0.1 M sodium cacodylate buffer for 12 h. Then the samples were washed in ultrapure water (NANOpure Infinity ® ; Barnstead/Thermo Fisher Scientific; Waltham, MD, United States) and dehydrated by ascending grades of ethanol series.…”