Thermal Stability Assessment of Fennel Seed (Foeniculum vulgare) Extract and Essential Oil in Soybean Oil During Storage Period

Oxidative degradation of oils, fats and high-fat food products during the processing and storage period, which leads to the reduction of organoleptic characteristics and nutritional value, is one of the most important challenges in the food industry. Adding antioxidants to foods is the most common method to reduce lipid oxidation rate. One of the most important features for a suitable antioxidant is the thermal stability during processing and storage period. In this research, the thermal stability of ethanolic and hexane extracts and essential oil of fennel seed compared to synthetic antioxidant BHA in soybean oil at temperature 90°C during a 28-day storage period by measuring peroxide, anisidine and oxidative stability indexes and totox value calculation were investigated. Extraction efficiency of extract with ethanol and n-hexane solvents and essential oil from fennel seed was obtained as 12.92%, 7.88% and 3.1%, respectively. The results of the research showed that the efficiency of all the studied antioxidants decrease during the storage period. Synthetic antioxidant BHA followed by fennel seed essential oil show the highest thermal stability. Ethanol and hexane extracts of fennel seeds did not show any significant difference with respect to the studied indexes and have the lowest thermal stability. As a natural antioxidant compound, fennel seed essential oil can be used as a substitute for synthetic antioxidants with proper thermal stability during the storage period.