Storage of a great amount of plum kernel waste becomes a challenge for food industry. In this work, the plum seed was used as a source of fixed oil that can be an ingredient of commercial products. Soxhlet extraction was carried out using the different solvents, such as n-hexane, n-heptane, ethyl acetate, acetone, or chloroform:methanol mixture (2:1 v/v). The highest yield of oil (about 30%) was obtained using n-heptane and n-hexane, while the lowest yield was obtained using ethyl acetate. The analysis of physico-chemical parameters indicated that all samples of plum seed oil have an exceptional quality. Schaal oven test indicated that the fixed oil of plum seed exhibited satisfactory oxidative stability at moderate storage temperatures (up to 65 °C). The composition of phenolic compounds in the oil samples was determined using HPLC method. The most abundant compound of seven identified and quantified phenolic compounds was vanillic acid. The highest content of β-carotene (1.67 mg 100 g-1 fixed oil) spectrophotometrically determined was in the oil extracted with n-hexane. The lowest content of β-carotene (1.26 mg 100 g-1 fixed oil) was determined in the oil extracted with a mixture of chloroform:methanol (2:1 v/v). This oil had the highest antioxidant activity (IC50 value of 4.35 mg mL-1) compared to other oil samples. The antioxidant activity was probably caused by the presence of phenolic compounds. The investigated physico-chemical properties demonstrated that the plum seed oil has a potential for application in the food, cosmetics, and pharmaceutical industry.
Keywords: HPLC analysis; antioxidant activity; oil extraction; oxidative stability; solvent polarity.