Influence of Tunisian aromatic plants on the prevention of oxidation in soybean oil under heating and frying conditions

• Rosemary and thyme enhance the oxidative stability of soybean oil.
• The addition of aromatic plants preserves tocopherols content.
• Phenol and volatile compounds from plants protect the oil quality during heating.
• The use of aromatic plants in oil improved the overall acceptability of potato crisps.

The aim of this study was to improve the oxidative stability of soybean oil by using aromatic plants. Soybean oil flavored with rosemary (ROS) and soybean oil flavored with thyme (THY) were subjected to heating for 24 h at 180 °C. The samples were analyzed every 6 h for their total polar compounds, anisidine values, oxidative stability and polyphenols content. The tocopherols content was determined and volatile compounds were also analyzed. After 24 h of heating, the incorporation of these plants using a maceration process reduced the polar compounds by 69% and 71% respectively, in ROS and THY compared to the control. Until 6 h of heating, the ROS kept the greatest oxidative stability. The use of the two extracts preserves approximately 50% of the total tocopherols content until 18 h for the rosemary and 24 h for the thyme flavored oils. Volatile compounds known for their antioxidant activity were also detected in the formulated oils. Aromatic plants added to the soybean oil improved the overall acceptability of potato crisps (p < 0.05) until the fifteenth frying.