Eight brands of liquid frying oils and four brands of solid oils that are commonly consumed in Iran were selected and each brand was coded with a letter (A, B, C, D, and…). Lot numbers were checked to ensure that each unit belonged to a different lot. All oil samples were stored, labeled and analyzed before expiry dates. Samples were selected to include the major manufacturers of the oils in Iran. The composition of studied oils was mixture of palm oil, soybean oil, canola oil, and sunflower oil. However solid oils contain more percentage of saturated fat.

All solvents and reagents were used of analytical grade. Methanol, n-Hexane, sodium hydroxide, methanolic boron trifluoride and sodium chloride were purchased from Merck, (Darmstadt, Germany).

The certified standard mixture of 37 component FA methyl ester C4-C24 was purchased from (Accuastandard, USA), also linoleic and linolenic acid methyl ester isomer were purchased from (Sigma, USA).

Methyl-esterification of samples used in the analyses was performed by BF₃-MeOH method according to AOCS (American oil chemist society) [16]. In to a 125 mL flask, one g of oil was weighted and added ten mL of 0.5 (N) methanolic sodium hydroxide solutions, the mixture was heated at 100˚C for 10 min, then 12 mL BF₃-MeOH reagent was added, and heated for extra 2 min. After cooling five mL of n-hexane was added. The reaction was stopped by adding 15 mL saturated solution of NaCl and shaking the flask for about 15 seconds. One mL of the upper organic phase was selected and anhydrous Na₂SO₄ was added. The sample solution was injected to the gas chromatography (GC) after filtering through 0.22 µm disposable syringe filter.

The GC-FID analyses were performed on an Agilent model 7890 GC instrument equipped with a flame ionization detector. A highly polar capillary column (100 m × 0.25 mm i.d × 0.25 µm film thickness) of HP-88 (Agilent, USA) was used to separate the FAMEs. Nitrogen was used as the carrier gas at a flow rate of 1.0 mL/min. A split ratio of 100:1 was used and 1 µL of the sample was injected into the GC for analysis. The following oven temperature program was used: 180˚C for 30 min, then increase to 200˚C at a rate of 1.5˚C/min and kept at 200˚C for 30 min. The temperature was set at 220˚C for the injector and at 250˚C for the detector. The samples were analyzed triplicate and the results were expressed as mean values ± standard deviation (SD).

Data were analyzed using statistical package for social sciences, version 16 (SPSS Inc., Chicago, IL, USA). Three independent oil samples of each cultivar were analyzed three times. Data are expressed as mean _ SDs. T-test was used for determining the differences between means inliquid frying oils and the solid oils. Statistical significance was set at p < 0.05.

The FA compositions of various brands of liquid frying oils in Iran are presented in Table 1. The mean of SFA in the brands ranged from 11.67% in C to 36.12% in A. Among the SFA palmitic acid presented the highest value ranging from 6.86% in C to 30.34% in D. High oleic oils (C18:1c) have better oxidative stability in deep frying applications and extended shelf life and reduced LDL [17]. Group A had maximum content of oleic (36.20%).

Table 1 shows that UFA ranged from 27.36% in A to 54.24% in C. Linoleic and linolenic acid are the most important PUFA. As nutritional point of view the amount of PUFA in oils is very important. Linoleic and linolenic have useful influence on human health and improve cardiovascular function. They also have positive effect on lipid profile [7]. Despite of these positive effects, high levels of multiple double bond FA increase oxidation oil sensitivity in liquid frying oil [17]. Therefore, high linolenic content was found in group C (3.85%) due to more oxidation tendency. According to the acceptable range of linolenic in Iran, standard reference and also Wolff report [18] on only C group with 3.85% mean percentage was