The impact of fish oil oxidation on interfacial properties and system stability of cod protein

In aquatic food multiphase interface systems, proteins and lipids coexist concurrently. Among them, lipids, particularly fish oil rich in polyunsaturated fatty acids, are susceptible to oxidation, resulting in oxidized products exhibiting similar interfacial activity as amphiphilic proteins. However, the interaction between oxidized fish oil products and proteins within the interface system remains unclear. As a result, this study is focused on investigating the effects of varying levels of oxidation in fish oil on the interfacial behavior of cod protein (CP), as well as on the stability, microstructure, and rheological properties of CP-fish oil emulsions. The findings revealed a significant decrease in interfacial tension (lower than 5 mN/m) at the oil-water interface after only 24 h of fish oil oxidation. Moreover, fish oil oxidation negatively influenced the behavior of cod protein at the interface, primarily manifested in the inhibition of infiltration, and rearrangement processes. Additionally, the oxidation of fish oil was found to significantly affect the centrifugal stability of the emulsion, resulting in a decrease in particle size, an increase in the absolute value of zeta potential, and improved rheological stability. The exploration of the interaction mechanism between fish oil oxidation and interface protein can offer scientific guidance for addressing the issue of uncontrollable product quality caused by fish oil oxidation in aquatic food process.