Improvement of antioxidant phytochemicals and color quality of green tea (Camellia sinensis L.) as influenced by cold plasma.

Background: Cold plasma (CP) was investigated as an innovative method to enhance green tea (Camellia sinensis) quality by improving extraction efficiency, bioactive retention. This study optimized dielectric barrier discharge (DBD) CP using air, argon, and nitrogen at 14, 18, and 22 kV for 6, 9, and 12 min to improve extraction and the qualitative and quantitative properties of green tea.

Results: CP treatments significantly impacted green tea traits. Argon and air gases, especially at higher voltages (22 kV) and longer durations (12 min), significantly increased hydrophilicity and phytochemical extraction, increasing yields by up to 48% compared to the control. These treatments had the highest total phenol [78.334 and 77.08 mg g^-1 dry weight (DW)], total flavonoid (8.09 and 7.72 mg g^-1 DW), antioxidant activity (80.74% and 81.93%), and catechins compounds content. Color properties, including brightness (L*) and greenness (a*), were enhanced compared to the control, with argon > air > nitrogen in effectiveness. Some treatments reduced color indices with higher voltage/time, while others increased them. Air and argon plasma (22 kV, 12 min) enhanced brightness, yellow-green color, and color purity in brewed tea. Principal component analysis (PCA) biplot confirmed that argon (18 and 22 kV, 12 min) and air (22 kV, 12 min) improved hydrophilicity, total phenol content, total flavonoid content, antioxidant activity, catechins, and color quality.

Conclusions: While argon and air plasmas were effective for extracting important phytochemicals, successful large-scale commercialization must consider costs, ionization potential, and energy usage, and so forth, of plasmas based on argon versus air. These findings can benefit the tea processing industry in producing higher-quality products for various sectors. © 2025 Society of Chemical Industry.