Interfacial Behavior and Antioxidant Efficiency of Olive Phenolic Compounds in O/W Olive oil Emulsions as Affected by Surface Active Agent Type

Abstract

The aim of this study was to evaluate the interfacial behavior of syringic acid, tyrosol and oleuropein, phenolic antioxidant compounds naturally present in olives and olive oils, and their ability to influence the stability to lipid oxidation of olive oil O/W emulsions. To test also the interactions of these molecules with other components and the effects on their activity, two different surfactants were used to prepare the olive oil emulsions, Tween 20, and a whey protein concentrate (WPC). All the antioxidants affected the olive oil/water interfacial tension; among them, oleuropein showed the highest interfacial activity and, thus, is supposed to locate at the interface. In emulsified state, the presence of the phenolic compounds in WPC emulsions did not cause any significant effect on the dispersion degree if compared to the control whilst a general improvement was observed in Tween 20-emulsions, in particular when oleuropein was added systems. The antioxidants were thus proven not to impair the dispersed structure but rather to improve it. As regards the oxidative stability, the antioxidants under investigation caused the occurrence of similar induction phases in the hydroperoxides production not observed in the control emulsions. In the case of secondary oxidation products, the highest inhibition was achieved in both the emulsified systems by oleuropein. In general, however, a lower amount of both primary and secondary oxidation products were observed in WPC emulsions than in Tween 20-emulsions likely due to the antioxidative effect of whey proteins.

Lipid Oxidation in Oil‐in‐Water Emulsions: Involvement of the Interfacial Layer

“…Antioxidants can be chosen so that their physicochemical properties lead to a preferred location at the interface. Some of them may intrinsically exhibit surface properties (Di Mattia and others , ), depending on their polarity, which is controlled by the environmental conditions (for example, pH [Pastoriza‐Gallego and others ; Costa and others ], and temperature [Pastoriza‐Gallego and others ; Losada‐Barreiro and others ]). The partitioning of antioxidants is also altered by the HLB of emulsifiers (Losada‐Barreiro and others ) and by the surfactant concentration through micelle formation (Richards and others ).…”

Enhanced yield of oleuropein from olive leaves using ultrasound‐assisted extraction

“…In recent years, attention has been focused also on the technological aspects of oleuropein, especially its use in emulsified food matrices. According to its amphiphilic structure, oleuropein has been shown to have surface activity and influences the emulsification process in model systems (Di Mattia, Sacchetti, & Pittia, ; Di Mattia et al., ; Souilem, Kobayashi, Neves, Jlaiel, et al., ; Souilem, Kobayashi, Neves, Sayadi, et al., ) and in complex formulations (Di Mattia et al., ; Giacintucci, Di Mattia, Sacchetti, Neri, & Pittia, ). Oleuropein has also been shown to inhibit oxidative phenomena in heterophasic systems (Paradiso et al., ).…”

From by‐product to food ingredient: evaluation of compositional and technological properties of olive‐leaf phenolic extracts

“…As already commented, the OLE extracts presented a rather complex composition; with regards to the phenolic pattern, oleuropein represented the main phenolic compound, followed by luteolin‐7‐glucoside, hydroxytyrosol glucoside, secologanoside, and ligstroside; however, the use of water or ethanolic solutions as extraction media did not cause any significant difference in the phenolic pattern, which thus cannot be considered responsible for the differences in adsorption behavior . It is not to be excluded the contribution of proteins and of other amphiphilic compounds as well as the formation of complexes with enhanced surface properties …”

“…8 It is not to be excluded the contribution of proteins and of other amphiphilic compounds as well as the formation of complexes with enhanced surface properties. 13,39,40…”