Effect of zahter (thymbra spicata L.) phenolic extract on oxidative stability of Şanliurfa butteroil

This study was conducted to investigate the effect of Zahter phenolic extract (ZFE) on the oxidative stability of Şanlıurfa pure butteroil. For this purpose, ZFE was obtained from the freeze-dried Zahter plant by ultrasound-assisted extraction method. Subsequently, induction time and estimated shelf life studies were conducted to determine the ZFE concentration in butteroil that exhibited equivalent oxidative stability to BHT. As a result of this evaluation, it was decided that the ZFE concentration with the longest shelf life and closest to the butteroil sample containing 75 mg/kg BHT was 75 mg/kg. In the next stage of the study, control (sample without antioxidant) and butteroil samples containing ZFE (75 mg/kg), BHT-S (75 mg/kg) and αT-S (75 mg/kg) were prepared and stored at 60, 70 and 80 °C for 120, 90 and 60 days, respectively. During the storage period, oxidative stability studies were carried out on butteroil samples by analyzing free acidity, peroxide value and p-anisidine at 10-day intervals. Then, kinetic modeling (reaction rate constant, activation energy and Q10 value) and thermodynamic coefficients of the calculated oxidation parameters (free fatty acidity, peroxide value and p-anisidine) in the control and different antioxidant containing butteroil samples were calculated. In this study, it was concluded that < 75 mg/kg ZFE could be used to provide oxidative stability equivalent to 75 mg/kg BHT in Şanlıurfa butteroil. On the other hand, it is recommended to carry out optimization studies to determine the appropriate ZFE concentration, as well as to purify the compounds that have antioxidant effects in the ZFE extract and use it in oxidative stability studies in butteroil.