Assessment of Cold Plasma Treatment Effects at Different Voltages and Exposure Times on Ephestia kuehniella Zeller, 1879 Mortality (Eggs, Larvae, and Pupae) and Physicochemical Properties of Treated Wheat Flour

Abstract This study investigated the effectiveness of cold dielectric barrier discharge (DBD) plasma treatment for controlling various developmental stages of Ephestia kuehniella,Zeller, 1879 a major stored-product pest, in wheat flour substrate. The experimental setup utilized a dual-power supply DBD system. Plasma treatment parameters were systematically varied across different life stages: Eggs received treatments ranging from 13 to 21 kV for 1 to 11 minutes, last-instar larvae were treated at 10 to 19 kV for 1 to 9 minutes, and pupae were subjected to higher voltages of 18 to 24 kV for durations between 5 and 13 minutes. Each treatment condition was replicated five times. Mortality assessment revealed significant stage-dependent susceptibility to plasma treatment. In eggs, optimal treatment conditions (19–21 kV, 9–11 minutes) achieved approximately 88% reduction in adult emergence compared to control groups. Larvae demonstrated the highest susceptibility, with 19 kV treatments inducing nearly 100% immediate mortality at exposure times of 5–9 minutes. Long-term monitoring showed sustained plasma effects, with mortality rates reaching maximum levels (nearly 100%) ten days post-treatment even at lower voltages. Pupae exhibited greater resistance, achieving maximum mortality of 65% at 24 kV for 13 minutes, compared to 33% natural mortality in controls. Analysis of plasma-treated wheat flour revealed minimal impact on quality parameters. Color analysis showed minor but perceptible changes with total color difference (ΔE) of 1.05 ± 0.83, slight reduction in chromaticity from 8.27 to 7.28, and marginal decrease in browning index from 32.69 to 32.52. SEM imaging demonstrated increased surface roughness and porosity in treated flour particles, indicating physiochemical etching effects. ATR FTIR spectroscopy showed structural modification in the treated flour, including increased carbonyl groups formation (1650 cm⁻¹), glycosidic bond breakdown (1000–1200 cm⁻¹), breakdown of hydrogen bonding networks (3400 cm⁻¹), and oxidation of aliphatic groups (2900 cm⁻¹).