Effects of Ethanol and Aqueous Extracts of Six Indigenous Spices on Listeria monocytogenes in Meat

Abstract

Aims: It was aimed at determining the antilisterial activity of aqueous and ethanol extracts of Thymus vulgaris L, Allium sativum L, Piper guineense Schum and Thonn, Monodora myristica (Garrtn) Dunal and Xylopia aethiopica (Dunal) A Rich and Ocimum gratissimum L. Study Design: The experiment was conducted in triplicates and mean values calculated. Place and Duration of Study: Department of Microbiology, University of Port Harcourt, Nigeria, between July and December, 2013. Methodology: Spices were separately extracted with ethanol and water. Effects of the extracts (0.1-5.0% and 1.0%) were determined against L. monocytogenes (1× 108 cell/mL) in agar well diffusion and treated meat pieces while untreated meat served as control using standard methods. Data were analysed using descriptive statistics, ANOVA and Scheffe for mean separation at p˂0.05. Results: Aqueous extract of P. guineense and T. vulgaris as well as ethanol extract of T. vulgaris inhibited L. monocytogenes growth at concentrations ranging from 1.0-5.0%, 0.5-5.0% and 0.1-5.0%, respectively. The reduction of L. monocytogenes attached to meat pieces varied during a 15 minutes immersion, ranging from 0.8 to 1.4 log10cfu/g. After 4-day storage at 30°C, L. monocytogenes exhibited significant higher growth in control samples compared to extract treated samples with initial population in log10 cfu/g increasing from 5.4-6.6 to 9.1-10.2 and 5.3-6.5 to 8.5-9.9 respectively.  There was no significant difference between control and treated samples stored at 10oC for 15 days, although initial population increased from 5.4-6.6 to 8.5-8.8 log10cfu/g and 5.2-6.5 to 8.2-8.5 log10cfu/g respectively. Conclusion: The result obtained in this study indicates the potential application of T. vulgaris in the control of L. monocytogenes.