Effect of thymus kotschyanus essential oil on the physicochemical and sensory properties of doogh

Chemical preservatives are usually used to reduce or eliminate pathogenic or spoilage microorganisms but their inordinate applications have resulted in toxigenic residuals and adverse effects on consumers, So many researches have been done to substitute the chemicals with naturally occurring compounds, especially plant essential oils. In this study, the chemical compositions of essential Thymus kotschyanus were identified with set GC-MS. Then organoleptic properties, microbial and physicochemical quality of Doogh sample prepared with adding different concentration Thymus kotschyanus essential oil were investigated during 14 day storage. Results of GC-MS analysis indicated that thymol (51.1 %), p-cymene (13.78 %) and γ-terpinene (9.03 %) comprised the highest amount of this EO. T. kotschyanus EO destroyed E.coli O157:H7 in addetive low concentrations to Doogh in same the early days and the MIC that determined by the micro dilution method was 470µg/ml. Based on the results, essential oil doesn’t have significant changes in Doogh physico-chemical properties excepion total solid that essentail Doogh free comparsion with Doogh contain 100 and 200 ppm make significant changes(p<0.05), the Doogh that contain 50 ppm was accepted by panelist. The addition of this EO has no adverse effect on the physicochemical and organoleptic properties of Doogh, also this EO effective substances could be purified and used as natural antibacterial agent, solely or along with others techniques, to prolong food shelf life.