Cold atmospheric-pressure plasma treatment of turmeric powder: microbial load, essential oil profile, bioactivity and microstructure analyses

Turmeric powder treated by cold atmospheric-pressure plasma (CAPP) at 25 kV for various times of 3, 5 and 7 min was examined for microbial load, essential oil profile, colour parameters, total phenolic content, total flavonoid content, antioxidant activity and microstructure. CAPP treatment caused a reduction of approximately 1.5 log CFU g⁻¹ in aerobic viable cell count of turmeric powder, which was most pronounced during the first 3 min of the treatment. The inactivation kinetic was fitted to the Weibull model with R² of 0.9913 and RMSE of 0.0641. Gas chromatography–mass spectrometry analysis of essential oils identified twelve different components for turmeric powder of which 1,8-Cineole, α-Terpinolene and trans-Caryophyllene were lost and ar-Turmerone and α-Zingiberene experienced considerable increases after plasma treatment. The double-edged effect of plasma treatment was also observed on bioactivity. Scanning electron microscopy showed formation of super-agglomerates in plasma-treated samples due probably to coalescence of the granules with plasma-damaged walls.