Effect of combinations of 3,4-dihydroxyphenylacetic acid and its esters on the oxidative stability of fish oil–containing trace water

The current study aims to comprehend the effect of the various combinations of 3,4-dihydroxyphenylacetic acid (3,4-DHPA) and its esters in varying molar ratios on retarding oxidation in bulk refined fish oil in the presence of 0.3% w/w water. All the esters and 3,4-DHPA exhibited better performance than the synthetic antioxidant butylated hydroxytoluene. In the presence of trace water, the parent compound was found to have a synergistic effect with hexyl ester when used at a molar ratio of 2:1, respectively, exhibiting a higher percent reduction among all the esters and their combinations. The study also showed that the presence of extraneous water can significantly accelerate the oxidation (twofold) in a bulk fish oil system. This suggests that the microenvironment of the oil is altered when water is present and that association colloids play a key role in enhancing the rate of oxidation. Thus, while designing a competent mixture of antioxidants, the specific site of oxidation involved and the surface-active components should be taken into consideration to efficiently retard oxidation.

Practical Applications: Analyzing the impact of trace amounts of water on the efficiency of natural antioxidants, including 3,4-DHPA and its lipophilic esters, helps to comprehend the required optimal antioxidant concentrations for such a dynamic bulk oil system. The study finds application in controlling oxidation in PUFA-rich oils containing surface-active minor components that can accelerate oxidation. The results of the study show that 3,4-DHPA and its esters could be a potential replacement for the synthetic antioxidant BHT in all aspects.