Batoko plum (Flacourtia inermis) peel extract attenuates deteriorative oxidation of selected edible oils

Abstract

The oxidation of oils has an adverse effect on the organoleptic properties and shelf-life of stored oils. Flacourtia inermis is one of the underutilized fruits grown in Sri Lanka with promising antioxidant properties. F. inermis peel extract (FIPE) was used to retard rancidity in edible oils. The efficacy of added FIPE (500, 1000, 2000 ppm) on sunflower oil (SO) and virgin coconut oil (VCO) was monitored at 3-day intervals at 65 ± 5 °C against a positive control (α-tocopherol at 500 ppm level) using Free Fatty Acid (FFA) and Peroxide Value (PV). Oils without FIPE were used as the control. Antioxidant efficacy (IC50) and Total Phenol Content (TPC) of FIPE were determined by DPPH assay and the Folin-Ciocalteu method. Fourier transform infrared spectroscopy was used to monitor the oxidative stability. The IC50 value and TPC of FIPE were 227.14 ± 4.12 µg·mL-1 and 4.87 ± 0.01 mg GAE/g extract, respectively. After 21 days, VCO (control) sample exhibited significantly (p < 0.05) higher FFA and PV than the treatments. FIPE exhibited comparable results with α-tocopherol. Conclusively, FIPE had strong antioxidant properties and thus, could be used as an alternative to α-tocopherol to improve the oxidative stability of virgin coconut oil and sunflower oil. However, only minor differences in the FTIR spectra were detected in treated and untreated virgin coconut and sunflower oil samples after 21 days storage at 65 ± 5 °C.