Effects of steam and lactic acid treatments on inactivation of Listeria innocua surface-inoculated on chicken skins

Effectiveness of combined steam (10 and 60 s, 70 °C and 98 °C) and chemical treatments, using concentrated solutions of lactic acid (1 and 30 min, 5% and 10% lactic acid), on the inactivation of Listeria innocua inoculated on the surface of chicken skins have been studied. Surviving bacteria on the skin were enumerated immediately after treatment, and after 7 days of storage at 4 °C. The most effective treatment was the combination of steam of 98 °C and 10% lactic acid with its immediate efficacy being mainly attributed to the applied heat treatment. However, after  7-day storage, the treatment's effectiveness was mainly due to the applied acid treatment, which prevented growth of the bacteria that survived the heat treatment. Milder treatments (70 °C steam, 5% lactic acid) revealed a genuine synergy between the heat and acid treatments, paving the way for an effective means of reducing bacterial load on the surface of poultry without affecting the product's “raw” appearance.