Development of a Spectrophotometric Assay with Mathematical Modelling to Unveil Optimal Combination for Antioxidant Synergy with Tocopherols in Oil-in-Water Emulsions

Tocopherols, the main natural antioxidants found in vegetable oils, can be more effective when combined with other antioxidants due to synergistic effects. Therefore, optimizing this synergy could significantly improve the prevention of lipid oxidation in food products. This effect is contingent upon the specific antioxidant molecules involved and is significantly influenced by environmental factors. Therefore, to assess and elucidate the involved mechanisms and the impact of environmental conditions, we established a rapid screening method using model oil-in-water emulsions. To this end, tung oil with varying concentrations of spiked tocopherols was emulsified in an aqueous phase. Subsequently, various polyphenol antioxidants were introduced, and the extent of oxidation was evaluated without exogenous radical initiator to avoid biasing potential chemical interactions involved in the synergistic action. The impact of the continuous phase nature revealed that oxidation kinetics could be significantly influenced by the type of buffer solution. The presence of oxidation inducer (metal ions) also shows an impact on the efficiency of the antioxidant combinations but also on their synergistic effects.   

Through this methodology, this study delineates the effectiveness of various antioxidant combinations with tocopherols in stabilizing emulsions against oxidation, considering different molar ratios and varying concentrations of tocopherols and their influence on synergistic effects. A mathematical modelling phase was developed to evaluate the antioxidant combinations (using an interaction factor index) and highlight their effect on both the initiation and propagation phases of lipid oxidation pathways These findings offer valuable insights into the mechanisms of interaction between antioxidants and tocopherols, paving the way for the development of more efficient antioxidant formulations. Moreover, this approach enables the evaluation of key factors such as the impact of pH or the specific isoforms of tocopherol on the observed antioxidant synergy.