Chemical Composition, Antioxidant and Antimicrobial Activities of Thymus capitata Essential Oil with Its Preservative Effect against Listeria monocytogenes Inoculated in Minced Beef Meat.
The chemical composition, antioxidant and antimicrobial activities, and the preservative effect of Thymus capitata essential oil against Listeria monocytogenes inoculated in minced beef meat were evaluated. The essential oil extracted was chemically analyzed by gas chromatography-mass spectrometry. Nineteen components were identified, of which carvacrol represented (88.89%) of the oil. The antioxidant activity was assessed in vitro by using both the DPPH and the ABTS assays. The findings showed that the essential oil exhibited high antioxidant activity, which was comparable to the reference standards (BHT and ascorbic acid) with IC50 values of 44.16 and 0.463 μ g/mL determined by the free-radical scavenging DPPH and ABTS assays, respectively. Furthermore, the essential oil was evaluated for its antimicrobial activity using disc agar diffusion and microdilution methods. The results demonstrated that the zone of inhibition varied from moderate to strong (15-80 mm) and the minimum inhibition concentration values ranged from 0.32 to 20 mg/mL. In addition, essential oil evaluated in vivo against Listeria monocytogenes showed clear and strong inhibitory effect. The application of 0.25 or 1% (v/w) essential oil of T. capitata to minced beef significantly reduced the L. monocytogenes population when compared to those of control samples (P-value  <0.01).
Laboratory of Protein Engineering and Bioactive Molecules (LIP-MB), Institut National de Sciences Appliquées et de Technologie (INSAT), BP 676, 1080 Tunis Cedex, Tunisia.
Nariman
N
El Abed
Laboratoire d'Epidémiologie et d'Ecologie des Parasites, Institut Pasteur de Tunis, BP 74, 1002 Tunis Belvédère, Tunisia.
Belhassen
B
Kaabi
Laboratory of Protein Engineering and Bioactive Molecules (LIP-MB), Institut National de Sciences Appliquées et de Technologie (INSAT), BP 676, 1080 Tunis Cedex, Tunisia.
Mohamed Issam
MI
Smaali
Institut National Agronomique de Tunisie, 1002 Tunis, Tunisia.
Meriem
M
Chabbouh
Institut Supérieur des Etudes Technologiques de Zaghouan, 1121 Mograne, Tunisia.
Kamel
K
Habibi
Institut Supérieur des Etudes Technologiques de Zaghouan, 1121 Mograne, Tunisia.
Mondher
M
Mejri
Laboratory of Protein Engineering and Bioactive Molecules (LIP-MB), Institut National de Sciences Appliquées et de Technologie (INSAT), BP 676, 1080 Tunis Cedex, Tunisia.
Mohamed Nejib
MN
Marzouki
Laboratory of Protein Engineering and Bioactive Molecules (LIP-MB), Institut National de Sciences Appliquées et de Technologie (INSAT), BP 676, 1080 Tunis Cedex, Tunisia.
Sami
S
Ben Hadj Ahmed