Red Wine-Enriched Olive Oil Emulsions: Role of Wine Polyphenols in the Oxidative Stability

Abstract

The benefits associated with the consumption of red wine due to its rich pool of phenolic compounds are well-recognized, thanks to the antioxidant activity related to these kinds of molecules. However, wine drinking should be done in moderation, or is forbidden for some populations for ethnic or religious reasons. One way to still enjoy the advantages of red wine is to use its dry extract. In order to test the ability of the red wine dry extract to reveal its antioxidant activity, it was solubilized in water to produce water-in-oil (W/O) emulsions based on olive oil. After the selection of the right emulsion composition, kinetics of oil oxidation were carried out in oil and emulsions in the presence of an increasing amount of red wine extract, whose presence influenced the rate of oxidation by slowing it down. This behavior was confirmed by monitoring the oxidation reaction in two ways; i.e., with the classical method that consists of the determination of the peroxide value, and with an accelerated test making use of 2,2′-azobis(2,4-dimethylvaleronitrile) (AMVN) and diphenyl1-pyrenylphosphine (DPPP). The first is a molecule that triggers the reaction at 40 °C, and the other is a molecule that by reacting with hydroperoxides becomes fluorescent (DPPP=O). Moreover, by comparing the emulsion structures observed by optical microscopy, no differences in the size of the dispersed aqueous phase were detected with the increase of the wine dry extract, which is an aspect that confirmed that the antioxidant activity was directly proportional to the wine extract concentration, and thus to the phenolic content.