Efficacy of rosemary (Rosmarinus officinalis L.) powder and extracts in the protection of refined and stripped hazelnut oil

Abstract

In this study, the antioxidant activity of rosemary (Rosmarinus officinalis L.) extracts or dried rosemary on the oxidative stability of hazelnut oil and its purified triacylglycerols (TAGs) was investigated. The antioxidant activities of rosemary extracts tested using different methods were similar to BHT and α-tocopherol at 0.25–20 mg/mL. Induction period (IP) is the time at which the onset of oxidation occurred was determined using differential scanning calorimeter (DSC) at 150 °C under oxygen pressure. The induction periods of hazelnut oils containing rosemary extracts (0.25–2.0 mg/g) and/or dried rosemary (10–200 mg/g) were higher than that of control at 150 °C, and their protection factors were in the range of 1.3 and 2.2. The induction period of hazelnut oil TAGs was 3.93 min, while those of TAGs containing rosemary methanol extracts at 1 mg/g or dried rosemary at 50 mg/g were 21.46 min and 27.19 min, respectively. According to the accelerated oxidation test at 60 °C, peroxide value, K232, and K268 values of hazelnut oil with rosemary extracts or dried rosemary were lower than those of control. Dried rosemary at 50 mg/g was the most effective supplement in hazelnut oil protection against oxidation. In conclusion, both dried rosemary and its alcohol extracts could be used to increase oxidative stability of hazelnut oil.