Effect of storage on microbial reductions after gaseous chlorine dioxide treatment of black peppercorns, cumin seeds, and dried basil leaves

Salmonella outbreaks linked to spices and herbs call for an effective inactivation process. Non-thermal technologies such as gaseous chlorine dioxide (ClO₂) has been explored for the decontamination of spices and herbs while minimizing quality deterioration. However, microbial inactivation post-ClO₂ treatment and post-treatment quality analysis has not been explored. This study monitored microbial survival in black peppercorns, cumin seeds, and basil leaves post-ClO₂ treatment for one week, and the color parameter, gas residuals, and byproducts were determined. One-week post ClO₂ treatment (10 mg/L) resulted in an additional increase in Salmonella reductions by 1.1, 1.0, and 1.4 log CFU/g in black peppercorns, cumin seeds, and basil leaves, and contributed to a total of 5.3, 5.0, and 4.7 log CFU/g reductions, respectively at 80% RH. The surrogate, Enterococcus faecium NRRL B-2354 populations were also determined at all treatment conditions; E. faecium showed lower microbial reductions than Salmonella in all samples, indicating its suitability as a surrogate for Salmonella during ClO₂ treatment. The color changes in black peppercorns and cumin seeds were negligible, while the color change in basil leaves after ClO₂ treatment was noticeable. The concentrations of gaseous ClO₂ in all three products were under the detection limit after being stored for one week. The byproducts such as chlorate, chloride, and chlorite at gas concentration of 10 mg/L were determined to be 0.48, 1.88, and 0.23 mg/g, 0.56, 8.32, and 0.25 mg/g, and 0.69, 10.41, and 0.02 mg/g in black peppercorns, cumin seeds, and dried basil leaves, respectively. In summary, extended storage time post ClO₂ treatment resulted in additional microbial inactivation, which can be considered while designing the decontamination of spices and herbs. ClO₂ gas concentration of 10 mg/L for 300 min was suitable for the decontamination of black peppercorn and cumin seeds.