The Impact of Atmospheric Pressure Cold Plasma (APCP) Sterilization Method on Bioactive Compounds and Microbial Load of Shirazi Thyme.

Atmospheric pressure cold plasma is a novel non-thermal method suitable for the decontamination of spices and medicinal herbs, offering minimal impact on food quality. This study investigated the effects of atmospheric pressure cold plasma on the sterilization of Shirazi thyme ( Zataria multiflora Boiss ) at different exposure times (2, 4, and 6 minutes) and voltages (10, 20, and 30 volts. The parameters evaluated included moisture content, total ash percentage, mold and yeast contamination, total bacterial count, essential oil composition, and sensory attributes of the treated samples. The results demonstrated that cold plasma treatment significantly reduced mold, yeast, and bacterial contamination levels, bringing them below the standard limits (p ≤ 0.05). GC-MS analysis of essential oil composition in the control sample identified twelve compounds: m -Cymene, Eucalyptol, trans-Linalool oxide, L-Linalool, 4-Terpineol, Carvacryl methyl ether, Thymol, Carvacrol, β-Caryophyllene, Ledene, Spathulenol, and β-Caryophyllene oxide. Among these, Carvacrol was the most abundant, comprising 19.35% of the total oil content. Comparison of volatile oil percentages between treated and control samples revealed a statistically significant reduction in the treated samples (p ≤ 0.05), with concentrations decreasing by a factor of approximately 3 to 8. Sensory evaluation results indicated that cold plasma treatment did not significantly affect aroma, flavor, or overall acceptability of the thyme samples compared to the control. In conclusion, the findings suggest that atmospheric pressure cold plasma, despite certain limitations, holds promise as an alternative sterilization method for thyme and may offer broader applications in the food industry.