Purpose: This study aimed at assessing the influence of washing water parameters (pH, organic load, temperature, chlorine concentration and time of contact) on inactivation of Salmonella during the disinfection step of minimally processed lettuce and carrots, mimicking practices used in MPV processing plants in Sao Paulo, Brazil.
Methods: Experimentally contaminated minimally processed lettuce (1 kg) or carrots (1 kg) were added to 8 l of water presenting pH 5.6 and 8.0, organic load 2.3 and 13.5 mg/l and chlorine 50 and 250 mg/l. The temperature of the water was 10 and 25°C and the time of contact was 2 and 20 min. Contamination was obtained by immersion for 30 min in water containing Salmonella (106CFU/ml). The tested parameters corresponded to the lowest and highest values encountered in the surveyed MPV processing plants.
Results: The combination of pH 8.0, organic load 2.3 mg/l, chlorine 250 mg/l, time of contact 20 min and temperature 10°C resulted in the highest reduction in the populations of Salmonella: 2.0 and 2.8 log for lettuce and carrot, respectively. Conversely, the combination of pH 5.6, organic load 13.5 mg/l, chlorine concentration 50 mg/l for 2 min at 25°C resulted in the lowest reduction: 0.5 and 1.1 log for lettuce and carrot, respectively. Factorial ANOVA test indicated that among the tested parameters, only chlorine concentration was significant (P<0.05) for reduction of Salmonella during the disinfection step.
Significance: Chlorine concentration is the most important parameter for reduction of Salmonella during the disinfection step of minimally processed lettuce and carrots, while pH, organic load, temperature and time of contact were less relevant.
Acknowledgements: FAPESP, CNPq and CAPES