Efficacy of gaseous chlorine dioxide for decontamination of Salmonella, Shiga toxin-producing Escherichia coli, and Listeria monocytogenes on almonds and peppercorns

Abstract Almonds and peppercorns have been implicated in outbreaks of foodborne illnesses. The objective of this study was to evaluate the efficacy of gaseous chlorine dioxide (ClO2) for pilot-scale decontamination of Salmonella, Shiga toxin-producing Escherichia coli (STEC), and Listeria monocytogenes on almonds and black peppercorns. Pathogens-inoculated almonds and peppercorns were exposed to ClO2 gas generated by mixing of sodium chlorite (NaClO2) and ferric chloride (FeCl3) in dry form or by dosing hydrogen chloride (HCl) into NaClO2. The concentrations of ClO2 (ppm) during the treatment duration (h) were recorded to obtain the cumulative ClO2 exposure (ppm-h), and the reductions in the pathogen populations resulting from exposure to the cumulative exposures were determined. For almonds, increasing the exposures from 983 to 10,408 ppm-h increased the reductions of Salmonella, STEC, and L. monocytogenes from 1.1 to 4.1, 1.6 to 4.1, and 1.4 to 4.1 log CFU/g, respectively. For peppercorns, increasing the exposures from 983 to 8039 ppm-h increased the reductions of Salmonella, STEC, and L. monocytogenes from 3.0 to 6.0, 3.7 to 7.2, and 3.2 to 7.3 log CFU/g, respectively. A 4.0-log reduction of the pathogens was achieved by using 10,408 ppm-h for almonds and 3112 ppm-h for peppercorns. Treatment parameters obtained from this study could be used in pilot-scale or larger decontamination applications for almonds and peppercorns.