Key factors affecting cold plasma composition: influence on plasma-activated water and food safety applications

Cold plasma (CP) is a partially ionized gas composed of ions, free radicals, photons, and electrons, whose concentrations of reactive oxygen and nitrogen species (RONS) are directly modulated by reactor parameters. Insufficient reporting of system configuration and plasma generation data compromises reproducibility and comparability in plasma-based applications. Based on Townsend's and Streamer's theories and extensive research, this study examined plasma formation mechanisms and identified 12 key parameters that influence the generation of reactive species, which must be consistently reported in plasma-based research. Characterization of these species, through optical emission spectroscopy (OES) or optical absorption spectroscopy (OAS), is fundamental for understanding plasma effects. This review highlights that optimizing promising applications, such as plasma-activated water (PAW) - a liquid with antimicrobial potential against various microorganisms - is challenged by inadequate descriptions of plasma treatments. PAW, characterized by reactive species such as NO₃^-, NO₂^-, OH, O₂^-, and H₂O₂, exemplifies how CP-forming parameters influence the effects of CP treatments. This work provides a solid theoretical foundation, essential parametrization, and characterization methods to guide future research and ensure reproducibility in CP applications, with particular emphasis on PAW.