Decontamination of fresh wet rice noodles using a vertical in-package cold plasma system

Abstract

Fresh wet rice noodles (FWRNs) have high moisture and starch content, providing a suitable environment for microbial growth. In this study, an in-package dielectric barrier discharge (DBD) cold plasma system operating in a vertical mode was used for the decontamination of FWRNs. The effects of applied voltage, dielectric barrier thickness, discharge gap, electrode area, and package atmosphere on electrical behavior and microbial inactivation of this system were systematically investigated. Within a stable discharge regime, applied voltages above 70 kV, dielectric barrier thicknesses of 2–12 mm, discharge gaps of 30–45 mm, and electrode areas exceeding 50 cm² were found to be necessary to achieve sufficient charge transfer and effective microbial inactivation, suggesting a practical engineering window for scale-up design. Oxygen, air, and modified gases (65% O₂ + 10% N₂ + 25% CO₂ and 70% O₂ + 30% CO₂) enhanced the decontamination efficacy compared with pure nitrogen. During refrigerated storage at 4 °C, in-package DBD cold plasma-treated FWRNs maintained total plate counts below 5 log₁₀ CFU g⁻¹ for more than 16 days, significantly longer than conventional thermal pasteurization (∼6 days), while better preserving textural properties, cooking quality, and visual appearance. Furthermore, a pilot-scale in-package DBD cold plasma system was constructed and validated for the decontamination of large-package FWRNs (300 g), indicating its potential to reduce microbial contamination and retard quality deterioration. Overall, these results provide essential insights linking reactor design, discharge characteristics, and microbial inactivation, supporting the development of scalable industrial in-package cold plasma equipment for commercial FWRN processing.