EFFICACY OF TRISODIUM PHOSPHATE IN KILLING ACID‐ADAPTED SALMONELLA TYPHIMURIUM

Abstract

ABSTRACTThe influence of acid adaptation on Salmonella Typhimurium tolerance to alkaline stress was studied using cells grown in buffered‐brain heart infusion (BHI) (pH 7.0) and BHI acidified up to pH 4.5 with acetic, citric, lactic and hydrochloric acids, and challenged in BHI containing 1.5%, 2.0% or 2.5% trisodium phosphate (TSP; pH 10.0, 10.5, 11.0, respectively) or NaOH at the same pH values. TSP was more effective in killing S. Typhimurium than NaOH (D values at pH 10.0, 10.5 and 11.0 of 28.3, 9.7, 2.77 min and 150.2, 31.5, 5.09 min with TSP and NaOH, respectively). Acid‐adapted cells showed a cross‐protection response to NaOH, with D values around twofold higher than those corresponding to nonacid‐adapted cells. However, they were more sensitive to a TSP treatment. These findings suggest that both alkalinizing compounds damage the cellular membrane in a different extent. A linear relationship between log of D values and treatment pH was found, obtaining zpH values (change in pH required for a 10‐fold reduction of D values) of 0.99 and 0.67 with TSP and NaOH, respectively. A surface response model was developed describing the combined effects of treatment pH and TSP concentration, which could prove useful for the food industry in determining appropriate processing conditions for decontamination purposes.PRACTICAL APPLICATIONSChemical decontamination processes are usually applied to reduce the potential pathogens load on food surfaces. This study explores the use of trisodium phosphate (TSP) as a decontamination agent effective in inactivating Salmonella Typhimurium in acidic foods, which represents a great concern for the food industry, health regulatory officials and consumers. A mathematical model has been developed, which enable us to predict the effect of treatment pH and TSP concentration on the inactivation of this pathogenic microorganism which could prove useful for the food industry.