Antioxidant Activity of Extracts of Phenolic Compounds From Rapeseed Oil Cakes

Oil cakes were prepared from commercial rapeseeds of the double‐low Bolko variety using a complete technological line. Samples of the oil cake containing 8.1, 9.9, 11.4, and 14.4% moisture were stored for 1, 2 and 3 months at 15C and a relative humidity of 78%. The content of total phenolics in the extracts so obtained did not depend on the moisture content of the oil cake or the length of storage; values ranged from 77 to 81 mg/g. In the extract obtained from nonpressed rapeseeds, a similar content of total phenolics (80 mg/g) was determined. UV spectra of the extracts studied were characterized by maximum absorbance at 330 nm. This wavelength indicates that sinapine was the main phenolic compound in the extracts. However, the extract obtained from the cake with the lowest moisture content and stored for 3 months exhibited a maximum absorbance at 328 nm. All the extracts showed good antioxidant activity, as assessed using a β‐carotenelinoleate model system. Antioxidative properties of extracts obtained from rapeseed cakes were similar to those of extracts from nonpressed seeds.