Penetration of Salmonella typhimurium into the turkey skins from three different defeathering systems (conventional, kosher, and steam-spray) was quantified by transverse sectioning of inoculated skins with a cryostat and fluorescent antibody staining of skin section homogenates. The microtopography of each skin observed by transmission electron microscopy was correlated with cell penetration. Although few cells were recovered due to freeze injury or freeze killing, direct plating of skin section homogenates showed the different properties of each skin for cell penetration. Fluorescent antibody staining recovered the most cells and revealed the cell distribution within the skin. In conventional skin, over 90% of cells resided in the upper 50 μm depth of skin, which implies the poor penetration of cells. Kosher skin showed relatively even distribution of cells up to 150 μm in depth, which indicated the penetration of cells even into the dermis. Steam-spray skin allowed the deepest (over 200 μm depth) and the highest number of penetration among the three types of skin. Conventional skin retained a thin layer of epidermis (0.3 ~ μm of stratum germinativum) on the surface, and it appeared to act as an effective physical shield against bacterial invasion. The loss of all epidermis on steam-spray skin could explain the deep penetration following this process. Kosher skin retained the most epidermis; however, the characteristic lengthy picking time in kosher processing caused mechanical damage to the skin and allowed deep penetration of cells.

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