effect of bakhtiari celery (kelussia odoratissma mozaff) on sensory properties and shelf life of set yogurt

background & aim: the essential oils are the most important secondary aromatic biochemical compounds in plants and even in some animals. they are of great importance because of their aromatic, flavoring and preventing properties from deterioration in food industries. according to ethnobotany study of aerial parts of bakhtiari celery or kelus (kelussia odoratissma  mozaffarian) in dairy such as yogurt and buttermilk, encouraged us to do this research.    experimental: in this study, the essential oil of k. odoratissima mozaff was extracted. evolution was made of three concentrations of essential oil (20, 40 and 60 ppm) which added to yogurt after inoculation. the yogurt made by industrial method. during 30 days with certain intervals physical, chemical and microbial properties were analyzed. results & discussion: the results showed that essential oil of k. odoratissima mozaff has improved significantly physical and chemical properties of yogurt. it led to increasing sensory properties, acidity control, improving flavor of yogurt and increasing time of consumption but water holding capacity (whc) was reduced. industrial and practical recommendations: it was proved that the best concentration of essential oil of k. odoratissima mozaff was 40 ppm.