Physicochemical properties of Iranian commercial olive oils

Types and contents of the chemical compounds found in olive oil, including fatty acids, antioxidants and pigments, indicates the oil quality, which in turn depends on several factors, including cultivar, climate, extraction method, and maturity of he olive fruit. Research has shown that tocopherol and polyphenol contents depend on cultivar and the cultivation region, respectively, while fatty acid content depends on both of these factors. Iranian olive oils have a different chemical composition and, consequently, different oxidative stability. Therefore, the aim of the present study was to investigate the chemical composition and physicochemical chartacteristics of commercial types of Iranian virgin and refined olive oils.

Iranian olive oils, including four virgin (C, D, F and H) and five deodorized (A, B, E, G and I) samples, as well as two foreign virgin samples (1 and 2) were purchased from local stores. To determine fatty acid compoition and compositional, chemical and physical indicators, national and international laboratory methods were used. All determinations were performed in triplicates.

The results showed that the main fatty acids in the Iranian commercial olive oils were monounsaturated fatty acids (MUFA), particularly oleic acid (C18:1); saturated fatty acids (SFA), particularly palmitic acid (C16:0); and polyunsaturated fatty acids (PUFA), particularly linoleic acid (C18:2). However, the compositional, physical and chemical characteristics, such as peroxide value, acid value, polar compounds, the unsaponifiable matters, phenolic compounds and tocopherols, which affect the oxidative stability of fats and oils, were significantly different among the different olive oils.

The available literature shows that no comprehensive research has been conducted on the physicochemical properties of commercial olive oils in Iran, despite the fact that the domestic production of olive oil, because of its special importance with regard to its more desirable fatty acid composition compared to other edible oils, as well as its unique microstructure, has had an increasing trend. Hence, investigation into the effects of climate and agricultural conditions on the properties of olives and a better knowledge of raw material characteristics will make it possible to produce edible oils with higher quality and greater stability.