Efforts to minimize the lipid oxidation in oil-in-water (O/W) emulsions have been made for many years. One of the most effective, economical and convenient employed strategies for food system is addition of antioxidants (AOs). Theaflavins (TFs) as an important group of AOs are reported to effectively inhibit lipid oxidation. The AOs efficiency in O/W emulsions depends not only on their rate constants of scavenging free radicals but also on their distributions. However, determining TFs distributions in intact O/W emulsions is not an easy task because of the physical impossibility of separating the interfacial region from the oil and aqueous regions. In this study, we employed a well-established pseudophase kinetic method on the basis of reactions between a hydrophobic 4-hexadecylbenzenediazonium ions (16-ArN2+) and the selected antioxidant to determine the distributions of TFs, including theaflavin (TF-1), theaflavin-3-gallate (TF-2), and theaflavin-3,3’-digallate (TF-3) in the stripped soybean oil/ Tween 20/ water based O/W emulsions. Results indicated that at the same emulsifier volume fraction, the order of the percentage concentrations in the interfacial regions followed %TF-3&lt; % TF-2&lt; %TF-1. It seemed that the selected TFs with less hydroxyl groups or galloyl groups were more prone to locate in the interfacial regions. An increase in emulsifier concentration promoted the incorporation of AOs into the interfacial region, however, their interfacial concentrations, which were much greater than their stoichiometric concentration, decreased due to the dilution of AOs in the interface region. Antioxidant activity and antioxidant efficiency of TFs were also analyzed to get a better understanding of the influence of antioxidant distribution and antioxidant activity on the antioxidant efficiency in inhibiting lipid oxidation in O/W emulsions. This research highlights the key role of the AOs interfacial distributions in inhibiting lipid oxidation in emulsions and is helpful for developing a guideline to select the optimal AOs for food emulsions in the future.

Distribution and antioxidant efficiency of theaflavins in stripped soybean oil/ Tween 20/ water based oil-in-water emulsions: application of a novel pseudophase kinetic method.

ACS Spring Meeting 2021

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