Lycopene in Soybean Oil: Identification of Oxidative Degradation Products and Effect on Oxidative Stability

Lycopene, a lipophilic ingredient, has been widely used in functional foods. However, most studies focus on the isomerization of lycopene and the oxidative degradation products of lycopene and their impact on oil systems are limited. In this study, the oxidative degradation products of lycopene in soybean oil were monitored during oxidation at 60°C, 120°C, and 180°C, respectively. Eight Z-isomers (4 mono-Z- and 4 di-Z-isomers) and 11 oxidative degradation products (3 aldehydes, 2 apo-carotendials, 2 epoxides, 1 acid, and 3 volatile products [6-methyl-5-hepten-2-one, 2,3-epoxy-geranial, and 3,7-dimethyl-2,6-octadienal]) were detected. Apo-6'-lycopenal and apo-8,6'-carotendial were identified as the main degradation product during thermal oxidation. Lycopene and its oxidation products have a protective effect on tocopherol in soybean oil at 60°C; however, they promoted oxidation at 180°C. Soybean oil with lycopene added showed significant color changes during storage and heating, and the value of a* was highly positively correlated with lycopene content. To preserve its visual characteristics, it is recommended to avoid high temperatures and prolonged heat treatment. The results provide theoretical support for the application of lycopene in functional food industry. PRACTICAL APPLICATIONS: Lycopene-enriched soybean oil can serve as a functional food ingredient, but its color and stability degrade under high temperatures. To maintain quality, avoid heating above 120°C and prolonged thermal exposure. This study guides optimal processing conditions for lycopene-fortified oils in products such as edible oils or nutritional supplements.