Thermooxidative stability of vegetable oils refined by steam vacuum distillation and by molecular distillation

Semi-refined rapeseed and sunflower oils after degumming and bleaching were refined by deodorization and deacidification in two ways, i.e., by steam vacuum distillation in the deodorization column Lurgi and by molecular distillation in the wiped-film evaporator. The oxidative stability of the oils before and after the physical refining has been evaluated using non-isothermal differential scanning calorimetry. Treatment of the experimental data was carried out by applying a new method based on a non-Arrhenian temperature function. The results reveal that refining by molecular distillation leads to lower oxidative stability of the oils than refining by steam vacuum distillation. Practical applications: (i) A method for the refining of edible oils by the molecular distillation in the wiped film of a short-path evaporator is presented and applied. (ii) Oxidative stability of the oils refined by molecular distillation and steam vacuum distillation is compared. It has been found that refining by molecular distillation leads to lower oxidative stability of the oils than refining by steam vacuum distillation. (iii) Experimental data were treated by applying a new method based on a non-Arrhenian temperature function. The method enables trustworthy predictions of oil stabilities for the application temperatures.