Effect of seaweed extracts on improving the oxidation kinetic of black cumin (Nigella sativa) oil

In this study, effects of red (Palisada perforata and Gracilaria corticata), brown (Sargassum angustifolium and Polyclada indica) and green (Ulva compressa and Caulerpa taxifolia) Persian Gulf seaweed extracts on thermal kinetic parameters of black cumin (Nigella sativa) oil was investigated in comparison with those of BHT and α-tocopherol. Oxidative stability of black cumin oil samples were investigated using Rancimat at 363, 383, and 403 K. Apart from P. indica extract, all other seaweed extracts were effective on improving oxidative stability indices of black cumin oil samples. Red seaweed extracts were the most effective in reducing the severity of temperature-related effects on black cumin oil oxidation rate. In addition, these antioxidants were able to reduce black cumin oil oxidation by forming an activated complex with more structured configuration. The extent of decrease in frequency factor and entropy were 80.77% and 14.83% for G. corticata extract, respectively and also 82.66% and 15.45% for P. perforata extract, respectively. The highest increase in Gibbs free-energy of activation was observed for G. corticata extract followed by BHT, P. perforata extract, and α-tocopherol. In conclusion, red seaweed extracts can be proposed as suitable sources of natural antioxidants for improving oxidation kinetic of black cumin oil.