Oxidative stabilization of cold-pressed sunflower oil using phenolic compounds of the same seeds

It is known that sunflower seeds are rich in phenols, constituting approximately 1-3 g per 100 g of seeds. The principal phenol is chlorogenic acid (CGA), followed by caffeic acid (CA) and lower quantities of several other compounds. On the contrary, it is known that phenols are present only in trace amounts in cold-pressed sunflower seed oils. In this study, the possibility of improving the oxidative stability of cold-pressed sunflower oil is evaluated using phenolic substances constitutive of seeds. Phenols, extracted from two different dehulled sunflower seed samples, were identified, measured and added to a cold-pressed sunflower oil and compared with butylated hydroxyanisole (BHA), pure CGA and pure CA. Raw phenolic extract (RPE) was composed of CGA exclusively, whereas CA was present only in traces in its free form was not present. On the contrary, hydrolysable phenol acids (HPAs) were constituted prevalently from CA, released by CGA alkaline hydrolysis. The stabilization effect on oil oxidation at 110degreesC was evaluated as 41% and 118% for RPE and HPAs respectively with respect to the control. At 30degreesC, no significant differences were recorded between the two seed extracts. Their antioxidant effect was lower than that at 110degreesC and evaluated to be, on average 13%. In comparison with BHA, at 30degreesC, both seed extracts were more effective than this synthetic phenol; at 110degreesC, the antioxidant effect of RPE and BHA was similar, whereas HPA was significantly more effective than BHA. In conclusion, this study demonstrates that the phenols present in sunflower seeds can be considered natural antioxidants suitable for stabilizing the oxidation of cold-pressed sunflower oil, at both low and high temperatures. (C) 2003 Society of Chemical Industry.