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

Abstract

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.

Frying Performance of High Oleic Oil Enriched in Biophenols during Discontinuos and Prolonged Thermal Treatment

“…Seed oils are generally poor of phenol compounds [6,7]. It was confirmed by our analytical results, whereonly 5.7 mg/L of phenols expressed as gallic acid were found in MIX C. With enrichment of oil in biophenols deriving from OMWW, a value of 339.8 mg/L of gallic acid was reached in fresh MIX P, an amount of about sixty times greater than the control.…”

“…Seed oils are generally poorer of phenolic compounds than olive oils [6,7]. The aim of this study was to evaluate oxidation stability of high oleic oil enriched in biophenols, comparing its performance with that of the same oil where no phenols were added, during discontinuous and prolonged thermal treatment.…”

Effects of the contents of impurities and seed hulls on the quality of cold-pressed sunflower oil

“…According to the results of the Rancimat test, the IP values (at 110°C) of the investigated oil samples (Table 4) were in the range from 3.63 h to 4.63 h, which is somewhat higher compared to the findings of De Leonardis et al (2003), who reported a value of 2.63 hours.…”

“…This assumes oil preparation solely by mechanical pressing on a screw press. After pressing, the oil is additionally purified by filtration or sedimentation, while no further quality improvement by refining is allowed (De Leonardis et al 2003;Matthäus & Spener 2008). Recent technological developments have enabled the manufacture of high-quality unrefined oils to be economically justified (Lanzani et al 1988;Contini & Moresi 1994).…”

“…In contrast to the refined oils, the sensory properties of cold-pressed oils preserve some of the characteristics of the source raw material and thus contribute to the formation of a specific aroma of the food, providing a special gastronomic pleasure (Dimić 2000;De Leonardis et al 2003). Sensory quality of unrefined oils is of essential significance as it points out to the potential omissions, errors, or irregularities in the oil production process ("burned" aroma), due to inappropriate storage of the material to be pressed ("mouldy", "musty" aroma) or prolonged oil storing ("rancid" aroma) (Rass et al 2008).…”