M.F. Slavik

Attachment of Salmonella typhimurium to skins of chicken scalded at various temperatures

Microtopography of chicken skin was studied by varying scalding temperature to determine the least favorable skin surface for salmonellae attachment. Birds were scalded at 52, 56, and 60°C, and the changes of skin morphology were examined by light and transmission electron microscopy throughout the whole processing. Breast skins obtained immediately after picking were inoculated with Salmonella typhimurium, and the attachment was quantified by using scanning electron microscopy and microbiological plating techniques. Skins scalded at 52 and 56°C retained most of the epidermis, although the latter temperature caused the loss of twice as much stratum corneum layers and produced a smoother surface than the former. Skins at 60°C began to lose most of epidermal layers during scalding and exposed dermal surface after picking, which was sometimes covered with thin fragmental epidermis or basal tissue. The number of salmonellae attached to 60°C-processed skins was 1.1~1.3 logs higher than those attached to the skins processed at 52 and 56°C, as measured by scanning electron microscopy. Microbiological plating, however, showed no significant difference in attachment among three skins processed at different temperatures. This was probably due to the insensitivity of the plating method to differentiate attachment strengths of salmonellae to the skin. The above results suggest that removal of whole epidermis should be avoided in processing to reduce salmonellae attachment to the skin.

Effect of electrical stimulation on bacterial contamination of chicken legs

Electrical stimulation was investigated as a method to eliminate or reduce the number of Salmonella typhimurium attached to chicken legs. Salmonellae-inoculated legs were attached to either cathode or anode or placed in an electrical field. In addition, the effect of electrical stimulation on various bacteria in an electrolyte solution was studied in order to determine the feasibility of using this method to prevent cross-contamination of poultry carcasses during processing. Stimulation was accomplished using a square wave with an amplitude of 8.5 to 14.5 volts, a frequency of 0.33 Hz or 100 KHz, and a duty cycle of 67%. Results indicate that electrical stimulation is effective in killing bacteria in solution and in reducing the number of salmonellae attached to chicken legs when legs are attached to anodes. Slight meat damage did occur, however, when chicken legs were connected to either anode or cathode1.z.