Influences of simultaneous physicochemical stresses on injury and subsequent heat and acid resistances of Salmonella Enteritidis in apple juice

The effects of prior simultaneous pH (3.0–8.0), water activity, aw (0.93–0.99) and temperature (3.0–62.0 °C) stresses on injury and subsequent resistance of Salmonella Enteritidis to acid (pH 3.78, 25 °C) and heating (pH 3.78, 55 °C) in apple juice were determined. Injury rates were significantly (P < 0.05) influenced by the linear effects of aw and temperature. Exposure to combinations (pH 4.0, aw 0.98, 15 °C) and (pH 5.5, aw 0.99, 32.5 °C) resulted in acid adaptation. Only the linear influence of prior aw stress significantly affected the subsequent acid resistance. Heat resistance was greatest after previous exposure to pH, aw and temperature ranges of 4.0–5.5, 0.96–0.98, and 15–50 °C, respectively. None of the stress factors significantly influenced subsequent heat resistance. These results provide a more realistic simulation of the effects of environmental stress factors on the behavior of S. Enteritidis in food and food processing ecologies; and contribute in further understanding the behavior of the pathogen for the improvement of evaluation and control of safety of apple juice and similar products.