Determination of the oxidative stability of cold pressed oils under different storage conditions

In the cold pressed flaxseed oil, grape seeds and black cumin oils, free acidity, peroxide value, specific extinction coefficients (K232 and K270) and fatty acid composition were determined as the initial analyses. For initial analyses free fatty acid, peroxide value, K232 and K270 values in the flaxseed oil, grape seeds and black cumin oils were detected to be 0.89%, 1.35%and 7.15%, 1.48, 12.21 and 26.55 meq O2/kg, 2.27, 3.43 and 4.15, 0.95, 3.96 and 1.13, respectively. In the flaxseed oil, grape seeds and black cumin oils with abundant unsaturated fatty acids, the ratios of oleic and linoleic acids being from the unsaturated fatty acids were observed to be 18.01%, 19.5%, 23.85%and 15.95%, 66.86%56,80%, respectively. In addition to these fatty acids in the flaxseed oil the ratios of linelonic acid were observed to be 56.55%. During the oxidation process the changes of peroxide value, specific extinction coefficients and volatile oxidation compounds were examined. At the end of 6th days of storage under the thermal oxidation conditions, the values of peroxide, K232 and K270 values for the cold pressed flaxseed oil, grape seeds and black cumin oils were detected as 29.54, 64.63 and 50.00 meq O2/kg; 6.41,13.62 and 10.41; 0.33, 3.74 and 1.34, respectively. At the end of 6th day of storage, for the flaxseed oil, the hexanal, 2,4- heptadienal and 2,4- heptadienal (E,E) values were recorded to be 24.28 x106, 16.84x106 and 16.09 x106 AU, for the grape seed oil the hexanal and the E-2-heptanal values were recorded to be 36.79 x106 and 67.53x106 AU, for the black cumin oil the hexanal and the E-2-heptanal values were recorded to be 36.79 x106 and 67.53x106 AU, respectively. At the end of 6th days of storage under light of cold pressed flaxseed oil, grape seeds, black cumin oils, the values of peroxide, K232 and K270 coefficients were measured to be 87.10, 357.71 and 329.06 meq O2/kg; 7.85, 17.14 and 11.55; 0.33, 4.55 and 1.53 respectively. At the end of the storage, the hexanal compounds in the cold pressed flaxseed oil were determined 4.40 x106 AU, the hexanal and E-2-heptenal compounds in the grape seeds and black cumin oils were determined to be 27.14 x106, 26.34 x106 AU and 41.72 x106, 32.81 x106 AU, respectively.