Antioxidative activity of sage (Salvia officinalis L.), savory (Satureja hortensis L.) and borage (Borago officinalis L.) extracts in rapeseed oil

The antioxidant activity (AA) of acetone oleoresins (AcO) and deodorised acetone extracts (DAE) of sage (Salvia officinalis L,), savory (Satureja hortensis L.) and borage (Borago officinalis L.) were tested in refined, bleached and deodorised rapeseed oil applying the Schaal Oven Test and weight gain methods at 80 degreesC and the Rancimat method at 120 degreesC. The additives (0.1 wt-%) of plant extracts stabilised rapeseed oil efficiently against its autoxidation; their effect was higher than that of the synthetic antioxidant butylated hydroxytoluene (0.02%). AcO and DAE obtained from the same herbal material extracted a different AA. The activity of sage and borage DAE was lower than that of AcO obtained from the same herb, whereas the AA of savory DAE was higher than that of savory AcO. The effect of the extracts on the oil oxidation rate measured by the Rancimat method was less significant. In that case higher concentrations (0.5 wt-%) of sage and savory AcO were needed to achieve a more distinct oil stabilisation.