Influence of Applied Voltage on Bacterial and Fungal Inactivation Using Double Dielectric Barrier Discharge Plasma

Abstract

The application of non-thermal plasma (NTP) in food sterilization has emerged as a promising technology for achieving microbial safety without compromising product quality. This study investigates the influence of applied voltage on the inactivation efficiency of bacterial and fungal contaminants in selected dried fruits figs (Ficus carica), apricots (Prunus armeniaca), and raisins (Vitis vinifera) using a Double Dielectric Barrier Discharge (DDBD) plasma system. Experiments were conducted under constant frequency (1.97 Hz), current (1.7 A), and airflow (2 L/min), while voltages were varied at 25 kV, 35 kV, 45 kV, and 50 kV for 10-minute exposures. Microbial analyses measured Total Viable Count (TVC) and Total Fungal Count (TFC) reductions across treatment levels. Results revealed a significant voltage-dependent decline (p < 0.05) in microbial loads. The highest bacterial and fungal reductions were achieved at 50 kV, with TVC decreasing by up to 44.5% and TFC by 50.5%, particularly in figs. The enhanced antimicrobial activity at higher voltages was attributed to increased generation of reactive oxygen and nitrogen species (ROS and RNS), which induce oxidative stress, membrane disruption, and DNA damage in microbial cells. These findings demonstrate that voltage optimization is critical for maximizing plasma-based decontamination efficiency while maintaining food integrity. The study provides strong evidence supporting the industrial potential of DDBD non-thermal plasma as a sustainable, chemical-free, and energy-efficient approach for microbial control in dried fruit processing.