Disinfection with sodium hypochlorite to contaminated lettuce by Escherichia coli O157:H7

Abstract

Aims: to check the effectiveness of recommended hypochlorite concentrations to disinfection of raw vegetables.

Materials and methods: lettuce leaves contaminated with Shiga toxin-producing Escherichia coli O157: H7 were exposed to treatments based on NaClO concentration, pH and time. The measured response was the logarithm of N / N0.

Results: it was observed that chlorine concentration and time have a significant effect (p <0.05). The time was the most important linear variable, it has the highest regression coefficient. The largest reductions were obtained with 200 ppm at pH 7 and 8 in 30 minutes. No reduction reaches the five logarithms suggested for a good sanitizer.

Conclusions: it is not safe to wash with NaClO in the proportions that would be used by a housewife or food establishment. Pathogens as the studied, with low infective dose and adherence, could remain in the contaminated vegetables.