In today's society, preparing healthy food has become challenging due to the variety of food production methods. Oil is produced in several ways in our country. In the cold pressing method, there is insufficient monitoring of the manufactured product. The aim of the present study is to investigate the physicochemical characteristics and the levels of heavy metals of industrial oil compared to cold-pressed oil.

In this research, 54 samples of sunflower, sesame, and canola oil produced by both cold pressing and industrial refiningmethods were prepared. Their physicochemical characteristics, including refractive index, acid value, iodine value, saponification value, peroxide value, anisidine value, as well as the concentrations of lead, iron, arsenic and copper were determined. Additionally, the effect of storage time on these characteristics was investigated.

The Iodine number showed the highest deviation from the standard (61%), with an average of 136.70 gI/100g for the cold-pressed oil and 134.48 gI/100g for industrially refined oiland. The average value of the physicochemical characteristics, except for the saponification value, were higher in the cold-pressed oil samples  compared to the industrially refined oil samples, but the observed difference was not statistically significant. An investigation into the effect of storage time on physicochemical properties revealed a significant increase in peroxide value (p<0.01) and anisidine (p <0.05) in both oil groups over a two-month period. The average concentration of arsenic, lead, iron and copper in the studied oils was 0.03, 0.78, 0.05 and 0.05 mg/kgoil, respectively. A deviation from the standard was observed only in one sample of cold-pressed sunflower oil, with an arsenic concentration of 0.11 mg/kgoil).

Based on the obtained results, the refined industrial oils exhibited more favorable chemical characteristics and stability.  It is suggested that cold-pressed oils should be consumed within a short period of time. For frying purposes, refined industrial oils are preferable.