Efficacy of blue light-assisted ClO2 for Salmonella decontamination on basil leaves: inactivation kinetics, quality preservation, and microbiota dynamics

Frequent Salmonella outbreaks associated with basil leaves highlight the need for effective postharvest decontamination. Conventional microbial sanitizers often fail to inactivate pathogens while preserving product quality, creating a demand for novel decontamination technologies suitable for basil. In this study, the microbial safety of basil under typical consumption scenarios was evaluated and a blue light-assisted ClO2 (COM) decontamination process for basil leaves was developed. Mathematical models were used to describe the microbial inactivation kinetics, and a systematic comparison was conducted against traditional single-chemical sanitizers (H2O2, HClO, ClO2, and 75% ethanol) in terms of microbial safety and final product quality. Results showed that simulated cooking scenarios, including pizza baking and hot soup immersion, were insufficient to reduce the Salmonella levels below the detection limit (<10 CFU/g) under a high initial load of 9.7 log CFU/g. Compared to the single-chemical treatments, 100 mg/L COM treatment achieved significantly higher decontamination (p < 0.05) by reducing Salmonella and background microbiota by 4.8 and 3.5 log CFU/g, respectively, with treatment time of 15 min. The inactivation kinetics of Salmonella showed a non-linear inactivation kinetics, which was captured by the Weibull model with a low RMSE value (RMSE = 0.16), although the AICc value (11.37) indicated limited model parsimony. Furthermore, the COM treatment significantly reduced bacterial richness (with the Chao1 index decreasing from 316 to 71) and effectively inactivated key spoilage organisms (Pseudomonas) as well as members of the Enterobacteriaceae, Actinomycetota, and Bacillota groups. Compared with the 100 mg/L ClO2 treatment alone (1.40 mg/kg), the 100 mg/L COM treatment resulted in a ClO2 residue concentration below the detection limit, without significantly altering visual appearance, color, chlorophyll content, total phenolics, or polyphenol oxidase activity (p > 0.05). Overall, blue light-assisted ClO2 treatment effectively reduced microbial contamination and reduced ClO2 residues while preserving the physical quality of basil, representing a promising decontamination approach for the fresh produce industry.