Gaseous antimicrobial treatments to control foodborne pathogens on almond kernels and whole black peppercorns

Gaseous treatments with ClO2 and O3 on low-moisture foods (LMFs) have been reported for their efficient bacterial reduction without affecting the external quality of food. However, these studies were conducted on a small scale, which limits their application to LMF industries. We aimed to evaluate the effectiveness of gaseous antimicrobial intervention with ClO2 or O3 to reduce foodborne pathogens (Shiga toxin-producing Escherichia coli, serovars of Salmonella enterica, and Listeria monocytogenes) inoculated on almonds and peppercorns maintained under various conditions. Almonds were treated for over 4 or 6 h. Peppercorns were treated for over 2.5 or 4 h. Gaseous O3 treatment was used for 6 h on almonds and 2 or 4 h on peppercorns. Additionally, the effects of relative humidity (RH) during the treatment of peppercorns and post-treatment heating on almonds were evaluated. Heating at 65 °C post-ClO2 treatment yielded the highest bacterial log reduction of 4.6 CFU/g on almonds, while 80% RH resulted in 3.7-log bacterial reduction on peppercorns. Gaseous O3 resulted in maximum log reductions of 1.3 and 2.5 CFU/g on almonds and peppercorns, respectively. No visual damage was observed. In conclusion, ClO2 was more efficient than O3 and the treatment can be incorporated into industrial practices.