Bactericidal efficacies of acetic acid, citric acid, lactic acid, and mixed organic acids to eliminate Salmonella Typhimurium, Campylobacter jejuni, and Listeria monocytogenes were investigated. The studied concentrations were 0.25, 0.5, 1, 2, and 4 % for each organic acid and 0.5:0.5, 0.5:1, 1:0.5, 1:1, 1:2, and 2:1 % for mixed organic acids of lactic acid : citric acid. Adding 0.5 ml of each tested bacterial suspension into each concentration of acid solutions volumed 4.5 ml to yielded bacterial count 10[superscript 7] CFU/ml. After their contact time of 5, 10, 15 and 20 min, the results showed that mixed acids (2 % lactic and 1 % citric acids) and 4 % lactic acid were the most effectiveness which eliminated 3 species of tested bacteria within 5 min. The stability of mixed acids was very well, since they were still be able to eliminate all tested bacteria after keeping at 4 and 25 ํC for 1, 3, 5 and 7 days. A skin attachment model was used to determined bacterial eliminating efficacies of mixed organic acids on the chicken skins inoculated with S. Typhimurium, C. jejuni, or L. monocytogenes 10[superscript 5] to 10[superscript 6] CFU/cm[superscript 2]. After 30 min firmly attached, the bacterial inoculated skins were sprayed with mixed organic acids (2 % lactic and 1 % citric acids) compared with using water. Pressure of the spray-gun was set at 40-45 psi and applied for 10 seconds. Temperature of mixed organic acids were tested at 0, 25, and 55 ํC. Bacterial numbers were maximally reduce with mixture of 2 % lactic and 1 % citric acids at 55 ํC the variations in the reduction in the number of bacteria followed on varied with bacterial species. Of the pathogens tested, C. jejuni was the most susceptible to acids which was reduced 1.76 log[subscript 10] (98.2 % reduction) followed by S. Typhimurium which was reduced 1.55 log[subscript 10] (97.3 % reduction). L. monocytogenes was the least susceptible to acids which was reduced 0.91 log[subscript 10] (86.8 % reduction) after exposed 1 h and after storage 4 ํC for 24 and 48 h, bacterial numbers continuously decreased. Organic acid spray treatments caused slight color-change to yellow on chicken skin and left some sour odor. However, the differences of odor and taste after cooking could not be detected by sensory-trained panels. Acceptance of consumers on decision of purchasing raw acid- treated chicken was 94.4 %, but the acceptance was reduce to 41.6 % when having raw non-acid treated chicken samples for comparison.
