Organic acids are commonly used as a carcass wash to remove bacterial loads during food production. In this study the interactions of four organic acids with 145 Salmonella strains comprised of six different serovars from feedlot watersprinkled cattle were studied. The pH was determined at the molar MICs (MICMs) of the Salmonella strains. The concentrations of the undissociated and dissociated organic acids were calculated at the MICMs of the Salmonella strains using the Henderson-Hasselbalch equation. Since all Salmonella strains behaved similarly to the different organic acids, the results of the six different Salmonella serovars Anatum, Cerro, Gaminara, Kentucky, Meleagridis and Muenster hide and feces strains were treated as a single group for each organic acid, acetic, citric, lactic and propionic acid. Bacterial inhibition was not solely dependent on pH or on the undissociated organic acid species, but was correlated with the dissociated organic acid species. A small drop in the concentration of the dissociated organic acids may result in a large number of bacteria escaping disinfection. Therefore, an organic acid carcass wash may not provide the expected elimination of surface bacteria if the concentration of dissociated organic acid is not carefully controlled. We suggest to maintain a concentration of dissociated propionic, acetic, lactic and citric acids of 15, 16, 17 and 20 mM, respectively, when carrying out a carcass wash with these organic acids to remove Salmonella enterica strains.

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