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