Antioxidation Performance of Essential Oils of Herbs and Spices in White Mineral Oils.

White mineral oil (paraffin oil) is a colorless, tasteless and hydrophobic oil used in many different industries. The oil is prone to oxidation, which negatively affects its properties and performance. In this study, six different essential oils obtained from herbs and spices (Sage, Laurel, Basil, Rosemary, Thyme, Oregano) were added to pharmaceutical and technical grade white mineral oils at 0.1 - 0.8 % (w/w) concentrations. Light, heat and air were applied to induce and accelerate oxidation. The total acid number, viscosity, and DPPH radical scavenging activity of the oils were measured in addition to the TGA and DSC tests to evaluate the anti-oxidation performance of the additives. The results showed that combined heat and oxygen treatment was the most effective of the three conditions tested to cause oxidation. The highest DPPH scavenging activities were obtained with oregano and thyme essential oils (up to 59% and 54% DPPH increase, respectively) and DPPH% activity increased linearly with increasing essential oil concentration. Thermal analyses, total acid number and viscosity change data also suggested the essential oils of Thyme, Oregano and Laurel as the best antioxidant additives to be used in white oils.