Effects of Soursop flowers (Annona muricata L.) extract on chemical changes of refined palm olein stored at frying temperature
In this study, the antioxidant activity of soursop flowers extract in delaying palm olein oxidation at frying temperature was assessed. The oil was supplemented with the extract at concentrations 200–1800 ppm, and stored in the oven at 180 C for 6 days (4 h heating per day). Palm olein containing butylated hydroxytoluene (BHT) served as positive control while the same oil without antioxidant (Control) served as negative one, in order to monitor changes in oils. After each two heating days, oil samples were collected, and their chemical indexes were determined. Peroxide, para-anisidine, TOTOX, thiobarbituric acid and iodine values were the parameters evaluated. Additionally, the evolution of the fatty acid composition of each oil sample during the storage was assessed by gas-chromatography using a flame ionization detector (GC/FID). Generally, palm olein samples containing the natural extract have exhibited the lowest rate of oxidation, and were efficient in limiting the destruction of unsaturated fatty acids in oil at frying temperature. The order of effectiveness in inhibiting oil oxidation was the following: PO +AnM1800ppm> PO +AnM1400ppm> PO+AnM1000ppm > PO+ An.M600ppm> PO+ An.M200ppm> PO+ BHT200ppm = Control. From these results, it can be concluded that soursop flowers are a potent sources of natural antioxidants for stabilization of palm olein.
Keywords: Soursop flowers; Stabilization; Natural antioxidant; Palm olein; Frying; Oxidative stability