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Summary In this article, a new method for determining copper and iron in edible vegetable oils by using atomic absorption spectrometry is discussed. The metals were extracted from low quantities of oil (1–2 g) with a 10% nitric acid solution. The acid solution obtained can be injected directly into the atomic absorption furnace. The proposed method is simple and allows copper and iron to be determined in edible vegetable oils with a precision estimated below 15% relative standard deviation (RSD) for Cu and 10% for Fe.

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 110 • C was evaluated as 41% and 118% for RPE and HPAs respectively with respect to the control. At 30 • C, no significant differences were recorded between the two seed extracts. Their antioxidant effect was lower than that at 110 • C and evaluated to be, on average 13%. In comparison with BHA, at 30 • C, both seed extracts were more effective than this synthetic phenol; at 110 • C, 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.

A first pilot study to produce a food antioxidant from sunflower seed shells (Helianthus annuus)This article explains a laboratory procedure to produce an antioxidant from grinded, dehulled and partially defatted sunflower seeds. Initially, a solvent suitable to extract phenols was searched among different solutions of water mixed with ethanol, methanol and acetone at 40% (vol/vol) (each tested at pH 5, 7 and 9). Both the ethanol/water 60:40 (vol/vol) and the acetone/water 60:40 (vol/vol) mixtures proved to be suitable for the dephenolization of sunflower seed shells, but in the next steps of this research, the mixture ethanol/water 60:40 (vol/vol) at pH 5 was used. Secondly, the procedure to obtain the antioxidant product was defined, which consisted in hydrolysis of sunflower seed phenols with 1.25 N NaOH at room temperature for 60 min and finally the recovery of caffeic acid formed from chlorogenic acid with ethyl acetate. From 25 g of partially defatted sunflower shells, around 90 mg of powdery antioxidant product, consisting of 58% caffeic acid, was obtained. The antioxidant product, the caffeic acid standard and propyl gallate were added to different edible fats at the same dose of 240 AU (antioxidant units) per kg fat. A Rancimat test, at 130 7C and an air flow of 20 L h 21 , demonstrated that the effectiveness of the sunflower antioxidant product was essentially similar to that of the caffeic acid standard, but 15-20% lower than that of propyl gallate. In conclusion, dephenolization of sunflower seeds could be economically convenient, not only because a useful antioxidant can be produced, but also because the raw material composition can be improved for other uses.