Survival of Acid Adapted Salmonella typhimurium in Some Acidic Foods


Abstract: This study examined the effect of adaptation to acid on the survival of Salmonella typhimurium in mayonnaise, turnip juice and ayran (a drink made of yogurt and water). S. typhimurium was adapted to acid by exposure to hydrochloric acid at pH 5.8. Commercially available mayonnaise (pH 3.7), turnip juice (pH 3.1) and ayran (pH 4.2) were inoculated with acid adapted or nonadapted cells of S. typhimurium (2 x 10^6 cfu/ml). Mayonnaise and turnip juice were stored at 4 or 20 °C. Ayran was stored only at 4 °C. Acid adapted S. typhimurium was detectable in mayonnaise at 4 °C after 24 h and in ayran after 48 h, whereas no nonadapted S. typhimurium survived in mayonnaise and ayran after these incubation times. Adaptation to acid enhanced the survival of S. typhimurium in ayran and mayonnaise stored at 4 °C. Nonadapted cells could not be detected in turnip juice after 120 min at 4 or 20 °C; however, acid adapted cells were detected at 15,000 cfu/ml (4 °C) and at 900 cfu/ml (20 °C). Nonadapted and acid adapted cells were not detected after 24 h of incubation in turnip juice. This study showed that adaptation to acid enhanced the survival of S. typhimurium in some acidic foods.

Keywords: Salmonella typhimurium, acidic foods, acid adaptation

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