Antioxidant activity and phytochemical content of cold-pressed rapeseed oil obtained from roasted seeds

An analytic comparison was made of cold-pressed rapeseed oil produced from unroasted seeds and cold-pressed oil produced from seeds that had previously undergone roasting at temperatures of 140, 160, and 180 degrees C for 5, 10, and 15min. It was determined whether the duration and temperature of roasting have any qualitative and quantitative effects on the contents of the native antioxidants (tocopherol, PC-8, phenolic compounds, canolol, and phytosterols) found in rapeseed oil. At the same time, changes in the antioxidant activity of oils produced from roasted seeds were determined. It was shown that roasting has no significant effect on the quality of cold-pressed oils. The peroxide value of the oils ranged from 2.03 to 3.48meqO(2)/kg, while the acid value did not exceed 0.68mgKOH/g. Slight changes were observed in oils in terms of tocochromanol contents. A decrease was seen mostly in the level of the -T homologue, with an increase in the contents of -T and PC-8 (in oil from seeds roasted at 180 degrees C). In the oil from the unroasted seeds, the canolol content was 11.54g/g oil. It was shown that increases both in temperature and in duration of seed roasting result in a statistically significant increase in the canolol content of cold-pressed oils. For the seed roasted at 180 degrees C for 15min, this increase was fifty-fold (609.94gcanolol/g oil). The same roasting conditions also led to a twofold increase in the antioxidant activity of the oil. Practical applications: Cold-pressed oils are increasingly frequently chosen by consumers due to their reputation as good source of bioactive components. An obvious example of such a food product is cold-pressed rapeseed oil made from roasted seeds, in which the levels of canolola product of the decarboxylation of sinapic acidis markedly increased. This compound is ascribed strong antioxidant properties, as well as antimutagenic and anticarcinogenic properties. Such oils truly deserve to be labeled bioactive products.