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Title: Bacterial flora of skin of processed broiler chickens after successive washings in mixtures of potassium hydroxide and lauric acid

Author
item Hinton Jr, Arthur
item Cason Jr, John

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/13/2008
Publication Date: 8/22/2008
Citation: Hinton Jr, A., Cason Jr, J.A. 2007. Bacterial flora of skin of processed broiler chickens after successive washings in mixtures of potassium hydroxide and lauric acid. Journal of Food Protection. 17:1707-1713.

Interpretive Summary: Experiments were performed to examine changes in the number of bacteria found on chicken skin after several washings in a soap-like solution (KOH-LA) that kills bacteria. Some bacteria on chicken skin can cause human foodborne diseases; therefore, treatments that reduce the number of bacteria on chicken products may decrease the number of foodborne diseases associated with the consumption of contaminated chicken. During these experiments, pieces of chicken skin were washed in water or KOH-LA for up to 5 times. After each wash, the number of bacteria remaining on skin was determined. Results indicated that large numbers of some types of bacteria could still be recovered from the skin after washing in fresh water for 5 times. However, repeatedly washing skin in KOH-LA removed several types of bacteria that were not removed by washing skin in water. KOH-LA acts like a soap that increases the cleansing ability of water and also kills the bacteria by making holes in the wall of these microorganisms. Bacteria that are firmly attached to the skin, such as staphylococci, are normally found on the skin of live, healthy chickens. Other bacteria, such as E. coli, are found mainly on the feathers and in the feces of healthy chickens and attach to the skin during processing. Although staphylococci were the most difficult type of bacteria to remove from skin, washing skin in KOH-LA decreased the number of both of these groups of bacteria on chicken skin. Findings of this study indicate that even though poultry skin may be contaminated by several types of bacteria, washing in solutions such as KOH-LA can reduce the number of these bacteria found on the skin of processed poultry.

Technical Abstract: Changes in the size of the populations of different groups of bacteria in the normal flora of the skin of processed broilers were examined after each of five consecutive washings with mixtures of potassium hydroxide (KOH) and lauric acid (LA). Skin from commercially processed broiler carcasses was used in the studies. Portions of skin were washed in distilled water (control) or in mixtures of 0.25% KOH-0.50% LA or 0.50% KOH-1.00% LA by using a Stomacher laboratory blender to agitate the skin in the solutions. After each wash, skin was transferred to fresh solutions and washing was repeated to provide samples washed 1 to 5 times in each solution. Bacteria in rinsates of the washed skin were enumerated on Plate Count (PC) Agar, Staphylococcus (STA) Agar, Levine Eosin Methylene Blue (EMB) Agar, Lactic Acid Bacteria (LAB) Agar, and Perfringens (PER) Agar with TSC supplement. Selected isolates recovered on each medium were identified. Results indicated that there was no significant difference in the number of bacteria recovered on PC, STA, or EMB agars from skin after repeated washing in water, but there were significant reductions in the number of bacteria recovered on LAB and PER agars. Repeated washing of skin in 0.25% KOH-0.50% LA or 0.50% KOH-1.00% LA generally produced significant reductions in the number of bacteria recovered on all media. Furthermore, no bacteria were recovered on PER agar from skin washed 5 times in 0.25% KOH-0.50%. Likewise, no bacteria were recovered on EMB or LAB agars from skin washed 3 or more times in 0.50% KOH-1.00% LA or on PER agar from skin washed 4 or 5 times in this solution. Staphylococcus spp. were identified as the skin isolates that were most resistant to the bactericidal activity of KOH-LA while species of Escherichia, Proteus, Clostridium, and Lactobacillus were more susceptible to the bactericide. Findings indicate that although bacteria may be continually shed from poultry skin after repeated washings, bactericidal surfactants can be used to remove and kill several types of bacteria found on the surface of the skin of processed broilers.