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

The purpose of this study was to evaluate the synergistic sporicidal effects of the ethanol extract from T orilis japonica fruit on inactivation of B acillus subtilis spores induced by UV irradiation at a wavelength of 254 nm. UV 254 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 UV 254 irradiation and 1.0% ethanol extract of the fruit produced 4.2–5.0‐log reductions of B acillus 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 B acillus and C lostridium genera, are the target of sterilization in various foods. The present study suggests that a combined treatment of UV irradiation and natural antimicrobial component, T orilis japonica fruit extract, can act synergistically and effectively to kill B acillus spores and can be a potential nonthermal sterilization method for the decontamination of B acillus spores in the food industry.