Kinetic Method for Determining Antioxidant Distributions in Model Food Emulsions:  Distribution Constants of t-Butylhydroquinone in Mixtures of Octane, Water, and a Nonionic Emulsifier

Abstract

The absence of reliable estimates of distributions of antioxidants in food emulsions hinders the development of a useful method for comparing the efficiencies of antioxidants. Here we describe the application of a pseudophase kinetic model, originally developed for homogeneous microemulsions, to the determination of distribution constants of tert-butylhydroquinone, TBHQ, in a fluid, opaque, model food emulsion composed of the nonionic emulsifier C(12)E(6), octane, and water. This kinetic method should be applicable to a wide variety of charged and uncharged antioxidants in emulsions composed of charged and uncharged emulsifiers. The distribution constants for partitioning of TBHQ between the oil and surfactant film regions, K(O)(I), and the aqueous and surfactant film regions, K(W)(I), were obtained by fitting changes in first-order rate constants, k(obs), with emulsifier volume fraction for the reaction of 4-hexadecyl-2,6-dimethylbenzenediazonium ion, 16-ArN(2)(+), with TBHQ. The rate of formation of the reduced arene product hexadecyl-2,6-dimethylbenzene, 16-ArH, was followed by HPLC. About 90% of the TBHQ is in the surfactant film at about 2% volume fraction of C(12)E(6), which suggests that this region may be the primary site of antioxidant activity for neutral phenolic antioxidants.

Determining α-tocopherol distributions between the oil, water, and interfacial regions of macroemulsions: Novel applications of electroanalytical chemistry and the pseudophase kinetic model

“…Rates of reactions of arenediazonium ions with AOs are sensitive to both temperature and pH and both must be carefully controlled to obtain reliable data [13]. Emulsions of 1:1 and 1:4 volume ratios of octane to water were prepared in a beaker by mixing together with a magnetic stirrer bar 5 mL of octane, 5 mL of aqueous 3 mM HCl, and 2 mL of octane and 8 mL of aqueous 3 mM HCl, respectively, and a weighed amount of C 12 E 6 (assumed density = 1 g/mL).…”

“…The problem is complex because AO effectiveness depends on a number of properties of the system such as the substrates being oxidized, the distribution of the AO within the emulsion, and the presence of free radical initiators such as transition metals [1]. AOs and polar solutes distribute between the oil, interfacial and water regions of the emulsion [7,13], but little is known about the fraction of AO in each region.…”

“…The approach is based on the pseudophase model for thermodynamically stable microemulsions [12][13][14]. Fig.…”

“…A variety of electron donors reduce arenediazonium ions [13,15]. Electrochemical reductions of arenediazonium ions have been studied in aqueous, nonaqueous, and micellar solutions [16][17][18][19][20].…”

Metabolic Kinetics of tert‐Butylhydroquinone and Its Metabolites in Rat Serum after Oral Administration by LC/ITMS

“…Meanwhile, it is found that they are limited in study of biological samples, such as analyses of metabolites, which is very important to study the pharmacokinetics and toxicology of TBHQ. HPLC coupled with mass spectrometry is a currently developed unique technique for monitoring antioxidant content and studying compound structure [11]. In particular, MS/MS triple quadrupole mass spectrometry in the multiple reaction monitoring modes (MRM) provides surpassing speed, sensitivity and selectivity.…”