The Combined Effect of UV Irradiation and Ethanol Extract from T orilis japonica Fruit on Inactivation of B acillus subtilis Spores

Abstract The purpose of this study was to evaluate the synergistic sporicidal effects of the ethanol extract from Torilis japonica fruit on inactivation of Bacillus subtilis spores induced by UV irradiation at a wavelength of 254 nm. UV254 exhibited the strongest inactivation effect, with the level of spores being reduced by approximately 3.6‐ and 4.7‐log cycles, respectively, after 3 and 10 min of exposure at an irradiation distance of 15 cm. And an ethanol extract of T. japonica fruit at concentration of 1.0% reduced the spore counts by about 3.0‐log cycles for 1 h of treatment. Furthermore, a combined treatment with UV254 irradiation and 1.0% ethanol extract of the fruit produced 4.2–5.0‐log reductions of Bacillus spores at different growth stages for an exposure time of 3 min. The energy required from UV irradiation to inactivate the spores was 50% lower in the presence of 1% ethanol extract of the fruit than with UV irradiation alone. Practical Application Bacterial endospores, especially those of Bacillus and Clostridium genera, are the target of sterilization in various foods. The present study suggests that a combined treatment of UV irradiation and natural antimicrobial component, Torilis japonica fruit extract, can act synergistically and effectively to kill Bacillus spores and can be a potential nonthermal sterilization method for the decontamination of Bacillus spores in the food industry.