Effect of Steric Structure on the Mechanism of Antioxidant Activity of Alkyl Gallates in Soybean Oil Triacylglycerols—A Kinetic Approach

Abstract

From an interfacial phenomena standpoint, the effect of the alkyl chain length is evaluated on the mechanism of antioxidant activity of gallic acid ester derivatives (methyl, propyl, octyl, dodecyl, and stearyl gallates) in bulk phase oil. A combinational kinetic model is used to estimate the oxidation kinetic parameters, such as induction period, the maximum concentration of lipid hydroperoxides, and critical reverse micelle concentration. These kinetic parameters are estimated much better with the combinational model compared to the tangent method. The nonlinear behavior is observed for inhibitory activities of homologous series of antioxidants in soybean triacylglycerols. In terms of different kinetics parameters, including antioxidant effectiveness and activity, methyl gallate has the highest inhibitory effect during lipid peroxidation. Gallic acid and alkyl gallates are able to protect bulk oils against peroxidation (induction period > 336 h) in terms of the extent of their participation in the main reaction of chain termination and pro-oxidative side reactions of chain initiation, and anti-oxidative side reactions of chain propagation. Practical Applications: This work explains the effect of the esterification in the inhibitory activity of alkyl gallates, mechanism action of alkyl gallates in bulk oil systems, antiradical potency as a function of the interfacial phenomena, and free radical chain mechanism, the impact of antioxidant activity on critical reverse micelle concentration of hydroperoxides. Moreover, in this study, it is confirmed that the combinational kinetic model can be employed as a reliable method for determining the oxidation kinetic parameters.

Interfacial Effects of Gallate Alkyl Esters on Physical and Oxidative Stability of High Fat Fish Oil-in-Water Emulsions Stabilized with Sodium Caseinate and Osa-Modified Starch

“…Our previous studies showed that the optimal concentration of alkyl gallates with maximum efficiency in oil is 1.2 mM (Delfanian, Sahari, Barzegar, & Ahmadi, 2021). Hence, this concentration was used in oil, which is equal to 0.84 mM in the emulsion.…”

“…Selection of an efficient antioxidant is an essential challenge in emulsion-based foods because its efficiency depends on innate potency as a chelating agent or radical scavenger, concentration in the interfacial region, and interaction with other reactants and components (Delfanian, Sahari, Barzegar, & Ahmadi Gavlighi, 2021). The interfacial concentration of antioxidant molecules depends on their distribution between the aqueous, interfacial, and oil phases, which depends on the physicochemical attributes of the antioxidant (e.g., hydrophobicity, and degree of ionization) and environmental conditions (nature of the oil, oil-water ratio, and surfactant concentration, etc.)…”