Staphyloccus aureuss Control in Ground Beef Using Thyme Essential Oil Yiannis Samaras, Ioulia Kokosi, Christos Bolis, Nikolaos Malissiovas, Athinaida Mourelatou, Effimia Eriotou* Technological Educational Institute of Ionian Islands, Department of Organic Farming and Food Technology, Argostoli, Kefalonia, Greece, 28100
Introduction There is a trend in western society to consume fewer synthetic food additives. Plant essential oils could play a role as antimicrobials. Thyme essential oil was found to be an active antimicrobial in microbiological mediaa 1 (disc assay, MIC, death curve). In ths work, its activity is determined in ground beef as it is an appropriate food product.
Results
Baird Parker plates at 102 dilution over the time period of 60 min
GC analysis of thyme essential oil
Objectives The objective of this work was the evaluation of the antimicrobial activity of thyme essential oil on three strains of Staphylococcus aureus in ground beef..
Conclusions Determination of thyme oil lethal concentration
Materials & Methods yhe essential oil tested for antimicrobial activity was obtained by hy-T dro-distillation and its chemical composition determined by GC. The strains used were: Staphylococcus aureus ATCC 12600, ATCC 12598 , and ATCC 25923..
There was an over 5 log-cycle decrease in the bacteria number at 0.25% (v/w) oil consentration for all strains of S. aureus. The decrease was achieved within 45 min. Only 0.05% v/v of thyme essential oil was requiredd to achieve the same result in microbiological media, indicating that food ingredients do interfere with thyme oil's activity.
This data indicate that thyme essential oil can be used for the control of Staphylococcus aureus in foods. The concentration of thyme oil is 5fold higher than that required to achieve the same effect in the in vitro tests.
References 1
Determination of thyme oil lethal concentration: A series of sterilee stomacher bags were generated for each strain, containing 10 g of ground 7 beef,10 cfu/g of the bacteria strain and a different concentration of thymee o essential oil. Bags were homogenized, placed at 4 C for 4 hours, serial l diluted and plated onto Baird Parker plates.e
Samaras Yiannis, Marianthi Chanioti, George Koutroullis, Maria Tsiaousi and Effimia Eriotou. Antimicrobial Activity of Essential Oils on Staphyllococcus sp. Presented at SGM, Edinburg, March 2010.
. Determination of the time required for bacterial death: Portions of ground beef containing essential oil at the concentration causing a 5 7 log decrease in the bacteria number were inoculated with 10 cfu/g of a o staphylococcal strain and were placed at 4 C. Control ground beef samples with no added S. aureus cells were also prepared as well as control l samples with bacteria but no oil. Samples consisting of 10 g were taken periodically, serial diluted and plated onto Baird Parker plates..
The first two authors contributed equally to this work *Corresponding author's e-mail address:
[email protected]
We are grateful to the National Bank of Greece The Agricultural Cooperatives of Kefalonia
and The Vallianios Farm School of Kefalonia for funding students' travel expenses
