Effect of orange peel oil addition on oxidative stability and sensorial properties of refined olive oil

It was aimed to determine the antioxidant effect of orange peel by using cold pressed orange peel oil (CPOPO), powdered freeze-dried orange peel (FDOP), hexane (HE) and acetone (AE) extracts of FDOP. In this context various chromatographic and spectrophotometric techniques were used and sensorial assessment was performed.CPOPO was added to refined olive oil (ROO) at various concentrations in order to select the best concentration by sensory analysis. FDOP, HE and AE were added to ROO at same concentrations with CPOPO and the samples were evaluated afterwards for their antioxidant capacity by DPPH and ABTS methods, total phenolics and total carotenoids. ROO triacylglycerols (TAGs) was obtained by alumina column chromatography. The samples containing antioxidant structures of orange peel were added to ROO and ROO-TAG and the oxidation status was followed by peroxide and p-anisidine values of the samples oxidized at accelerated oxidation conditions (60°C during 24 day). Separately, induction periods of the samples were determined by rancimat apparatus at 130°C.Based on the sensory evaluation, addition of the CPOPO at the ratio of 0.5% was selected for following experiments. Depending on the addition methods such as direct addition of CPOP and FDOP or addition of solvent extracts of FDOP, considerably different DPPH and ABTS values were observed (P < 0.05) in TAGs and ROO. Compared to others, CPOP has the poorest antioxidant powers. The highest amount of total carotenoids and phenolics, which are accepted as antioxidant constituents, were observed in acetone extract (AE) added to ROO and TAGs. However, a weak antioxidative effect of total carotenoid contents in oil system was observed. DPPH antiradical activity of hegzan and acetone extracts in TAG system and HE in ROO were higher than that of other extracts. When ransimat IP values were taken into account, addition of AE to refined olive oil TAGs provided best protection (1.16 h) at analysis conditions, in contrary, ROO containing FDOP has the longest IP value (2.73 h).Compared to the control (ROO), addition of HE and AE to ROO prevented the formation of the peroxides at initial stages of the oxidation during accelerated oxidation. However, this effect decreased at prolonged oxidation days. When the oxidation levels of ROO-TAG were taken into account, ROO-TAG oxidized rapidly (peroxide value reached to 305.63±0.89 meq/kg at twelfth day) and the lowest peroxide values were observed in ROO containing AE at all of oxidation times. The similar results were observed for p-anisidin values in ROO-TAG containing AE. In addition, HE has also a small amount of antioxidant power in ROO-TAG.When the results were taken into account, it can be concluded that the antioxidant structures from orange peel can be used as antioxidant in essential oils, vegetable oils and the lipid containing foods.