Antimicrobial efficacy of gaseous chlorine dioxide for inactivation of Salmonella and Enterococcus faecium NRRL B-2354 on dried basil leaves

Abstract

This research aims to investigate the efficacy of chlorine dioxide gas on the inactivation of Salmonella on dried basil leaves and evaluate the suitability of E. faecium as a surrogate for Salmonella. Dried basil leaves (2.0 ± 0.1 g) inoculated with a 5-strain Salmonella cocktail or E. faecium were packed in a paper bag, heat-sealed, and placed inside a chlorine dioxide treatment chamber. The samples were exposed to different levels of gas concentration (5, 10, and 15 mg/L) and relative humidity (60, 70, 80%) for various exposure times. The treated samples were diluted with neutralizing buffer and plated onto tryptic soy agar modified to enumerate both microorganisms. The log-linear model was used to fit the inactivation data for both microorganisms. As the relative humidity increases from 60 to 80% at 10 mg/L, the D-value decreases from 70.5 to 41.8 min for Salmonella and 121.7 to 52.6 min for E. faecium. The modified Bigelow model performed better than the response surface model for estimation of the D-values. A greater resistance exhibited by E. faecium indicated that it may be used as an ideal surrogate for Salmonella during chlorine dioxide treatment of dried basil leaves.