Quantitative evaluation of low-level fumigation using a controlled vapor–liquid equilibrium model: Application to perillaldehyde and perilla essential oil

To enable the practical application of volatile chemical agents, including naturally derived compounds not yet widely used for disinfection, there is a need for a robust and reproducible evaluation framework capable of quantitatively assessing antipathogenic activity under both liquid- and vapor-phase conditions. However, the lack of quantitative performance metrics beyond conventional log reduction values and the difficulty in controlling vapor-phase concentrations in low-level fumigation have hindered the establishment of such evaluation systems.In this study, we established a controllable and quantitative evaluation framework for low-level fumigation. Under liquid-phase conditions, the minimum concentration required to achieve a > 3.5 log reduction was defined as a practical performance metric. Under vapor-phase conditions, a controllable vapor–liquid equilibrium-based model was developed to maintain reproducible quasi-steady-state vapor concentrations, and continuous performance metrics, including survival time and half-life, were introduced to enable reproducible performance evaluation. Perillaldehyde (PA) and perilla essential oil (PEO), renewable natural products, were selected as model compounds.Treatment with 1% PA (or 2% PEO) for 10 min and treatment with 0.5% PA (or 1% PEO) for 30 min achieved >3.5 log reduction against bacteria, yeast-like fungi, and enveloped viruses, but not against non-enveloped viruses. In addition, fumigation with PA and PEO reduced the survival time of these pathogens on glass and polyester surfaces by >70–90%.The proposed framework is applicable to a wide range of volatile agents and pathogens, and provides a reproducible quantitative framework for developing and comparing disinfection and preservation strategies under practically relevant conditions.