The effects of drying methods and gamma irradiations on total phenolic and flavonoid amounts, antioxidant capacities and phenolic compound contents of olive leaves

Abstract

The effects of drying methods such as infrared, ambient condation, microwave and convectional and different dosage gamma irradiations such as 3, 5 and 10 kGy/min on total phenolic and flavanoid amounts, antioxidant capacities and phenolic compound contents of Ayvalık and Gemlik olive leaves were investigated. The antioxidant capacities, total phenolic compound amount, total flavanoid amount and phenolic contents of the samples were determined by 2,2-diphenyl-2-picrylhydracyl hydrate (DPPH) radical scavenging method, Folin–Ciocalteu method, spectrophotometric and high performance liquid chromatography (HPLC), respectively. Microwave method was the most effective drying method in increasing the activity of phenolic, flavanoid and antioxidant compounds; gamma irradiations had different effects on phenolic compounds; the most abundant phenolic compound in olive leaf was oleuropein and the least found compound was gallic acid. In addition, the highest antioxidant content was obtained for Gemlik olive leaf, which applied 3 kGy/min gamma irradiation dosage and dried by microwave method.