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.
Highlights
Fats and oils play a vital role in the human diet owing to their nutritional value
The antioxidant efficacy of plant extracts can be tested using a wide variety of methods
Results of the present study revealed that the antioxidant activity of F. inermis peel extract (FIPE) (227.14 ± 4.12 μg·mL-1) was significantly (p < 0.05) lower than that of α-tocopherol (29.80 ± 3.22 μg·mL-1)
Summary
Fats and oils play a vital role in the human diet owing to their nutritional value. Soybean, palm, rapeseed and sunflower oil are identified as the most widely consumed edible oils. Sunflower oil is the second most widely used oil in Europe (Arshad and Amjad, 2012) and contains high amounts of vitamin E, essential fatty acids and a low level of saturated fat (Madhavi et al, 2010). Autoxidation and photosensitized oxidation (Choe and Min, 2006) which modifies organoleptic properties while affecting the shelflife (Lercker and Rodriguez-Estrada, 2002) with a strong impact on the final quality of foods (Capuano et al, 2010). This lipid oxidation contributes to decreasing the nutritional quality in addition to the production of rancid odors, unpleasant flavors and discoloration (Abdelazim et al, 2013). The oxidative stability of edible oils is one of the major concerns in the food industry; and oxidative stability is defined as “resistance to oxidation during processing and storage” (Guillén and Cabo, 2002)
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