Fungal inactivation on Mexican corn tortillas by means of thyme essential oil in vapor-phase

Antifungal activity of thyme (Thymus vulgaris) essential oil (EO) in vapor-phase was tested against representative fungi in corn tortillas. The chemical composition of studied EO was analyzed by gas chromatography-mass spectroscopy, and its major components were linalool, thymol, and p-cymene. The antifungal activity was evaluated by determining the growth of Aspergillus niger or Penicillium expansum after exposure to EO vapors. The in vitro minimum inhibitory concentration (MIC) of the EO was determined by the inverted lid technique, while in situ MIC was determined on the corn tortillas inside an airtight container. The MICs obtained ranged from 160 to 200 μL of thyme EO/L(of air) for in vitro conditions and 550–850 μL of the EO/L(of air) in corn tortillas. The modified Gompertz model adequately described in vitro mold growth curves. Thyme EO was effective in preventing or significantly delaying growth of the contaminating molds on corn tortillas.