Investigation extraction of rosemary leaves the phenolic compounds by ultrasonic technique and its effect on organoleptic properties, physicochemical and stability of virgin olive oil

Virgin olive oil due to having unsaturated fatty acids is exposed to various types of corruptions such as enzymatic reactions and lipid oxidation. One way to prevent oxidation of oils and fats is addition of antioxidants. Rosemary due to phenolic compounds and other antioxidant compounds have antioxidant as well. In this study, the extraction phenolic compounds of rosemary leaves in virgin olive oil with was performed using by ultrasonic technique. In this method, rosemary leaves with three levels (5, 7 and 10%) and three ultrasonic times (10, 15 and 20 minutes) were added to the olive oil. Phenolic compounds present in the extracts, was measured. The results showed that in the ultrasonic method the sample of virgin olive oil with 10% rosemary and 10 minute extraction time has the highest total polyphenols (457.59 ppm). In this case study the effect of this extract in retarding oxidation of virgin olive oil during the 4-month by determining the peroxide value, thiobarbituric acid, oxidative stability, at the end of each month were reviewed. After four months keeping, the ultrasonic's peroxide number, the thiobarbituric acid (20.75meq O₂/kg oil, 1.32 molonaldehyde/kg oil, respectively) significantly decreased. The results of antioxidant activity of the extracts using rancimat method showed that during the period of induction at 110 °C in the ultrasonic's sample (29.10 hours) with respect to control's sample (6.28 hours) are increased. The acidity value of the ultrasonic's sample (2.05 FFA %) and thermal's sample (1.84 FFA %) are less than the control's (3.18 FFA %). Measurement results showed that the amount of chlorophyll pigments within ultrasonic's sample (1.4mg/kg) had the highest value and with respect to control's sample (0.63mg/kg) had high value. Also in the sensory evaluation, the ultrasonic's sample has top rated in terms of taste, odor, bitter and won general acceptance. Therefore, the phenolic compounds in the olive oil containing rosemary and extracted by ultrasonic method, be able to retard the oxidation process well. Thus, rosemary can be recommended as a source of natural antioxidants for increase virgin olive oil oxidative stability.