Assessing the impact of cold plasma rotational dynamics on ginger's total phenolic content, antioxidant activity, surface structure and color using response surface methodology

Abstract

This study investigated the efficacy of a rotational chamber in enhancing the effectiveness of cold plasma application to augment antioxidant activity and phenolic content in ginger ( Zingiber officinale ). To address the limitation of cold plasma (CP), which predominantly treats only the surface layers of samples, we implemented rotational techniques during the treatment. This methodology facilitates a more uniform treatment, ensuring that all layers of the samples are effectively exposed to plasma. We employed response surface methodology (RSM) to analyze the effects of three variables: power (10–90 W), treatment time (1–30 min), and pressure (0.4–0.9 mbar), along with a categorical variable for rotation. CP treatment (65 W, 0.7 mbar, 1 min with rotation) resulted in a significant increase in antioxidant activity compared to non-treated samples, determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric-reducing antioxidant power (FRAP), and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) ABTS assays, and total phenolic content reaching their highest values of 100.9 Trolox equivalent (TE) μmol⋅L −1 , 8.23 Fe 2+ ⋅g −1 , 0.293 μmol⋅g −1 , and 32.80 gallic acid equivalent (GAE)/g, respectively. There were no significant changes in color. Scanning Electron Microscopy (SEM) analysis revealed that the samples treated with CP exhibited a smoother surface, albeit with minimal damage to cell walls in our selected samples. Including a rotational feature as a unique upgrade to the cold plasma, the glow discharge device demonstrated positive enhancements and preservation of antioxidant activity and phenolic compounds. • Rotary low-pressure cold plasma performed effectively. • Rotary low-pressure cold plasma increased the antioxidant activity. • Rotary low-pressure cold plasma increased phenolic compounds. • The sample's surface became smoother after minimal cold plasma treatment.