Determination of physicochemical properties of irradiated sumac (Rhus coriaria L.) fruit oils

Abstract

Sumac fruit is widely used both in Turkey and in many countries of the world in the food industry, especially in spices and seasonings, and in many other areas. Gamma irradiation is a food preservation method applied in the food industry, especially in the spice industry, in terms of food safety. Gamma irradiation was applied to sumac fruits (2.5, 5.0, 7.5 and 10 kGy) to obtain microbiologically safe products, especially for consumer health. After the irradiation process, the extraction of crude oil of sumac fruit samples was performed by the soxhlet method and then free fatty acid content, peroxide number, fatty acid composition and tocol and sterol compositions of these oils were determined. In addition, the total phenolic substance amounts of the samples were determined by using the Folin-Ciocalteu reagent method and the antioxidant activity values were determined by DPPH•(2,2-diphenyl-1-picrylhydrazil) free radical reduction activity measurement. In parallel with the increase in irradiation dose, free fatty acidity and peroxide values of sumac fruit oil increased. Considering the acid compositions, the main fatty acid of sumac fruits was determined as oleic acid (43.43%). In addition, as the irradiation dose increased; palmitic (C16:0) and stearic (C18:0) acid ratios of saturated fatty acids and oleic (C18:1) monounsaturated fatty acids increased, while linoleic (C18:2) and linolenic (C18:3) acid as polyunsaturated fatty acids rates were decreased. According to the sterol and tocopherol composition of the sumac oil, it was detected that the most common sterol was β-sitosterol (78.51%) and irradiation did not cause a statistically significant change in the sterol composition, but the tocopherol composition decreased with the increasing irradiation dose. Finally, the total phenolic content and antioxidant capacity value of sumac oil samples decreased in parallel with the irradiation dose. As a result, it is recommended to irradiate the sumac fruit at lower doses, such as 5 kGy, without any negative effect on the quality of its oil.