Effect of vacuum thermoxidation on sunflower oil

In recent years vacuum frying was developed as an alternative methodology to traditional frying. In this study, sunflower oil thermoxidation was evaluated using conventional process conditions (180 °C and atmospheric pressure) and vacuum technology conditions (130 °C and 0,1 bar). Traditional thermoxidation lasted 20 h while vaccum thermoxidation was completed after 56 h. Total polar compounds reached 23 and 7,1 % at the end of atmospheric and vacuum thermoxidation respectively, while polymers content was 9,3 and 2,2 % for each oil. Tocopherols contents decreased 45 % for atmospheric thermoxidized oil and were reduced to 17 % for vacuum thermoxidized oil. These results clearly proved vacuum thermoxidation achieved a significantly lower deterioration rate than atmospheric thermoxidation of sunflower oil, conferring it much longer useful life and better nutritional qualities. Accordingly, a singnificantly slower vanishing rate of tocopherols was observed in vacuum thermoxidation.