Polyphenol-palmitate self-assembly in lipid systems: Implication of architecture on functionality

Polyphenol palmitate (PP) is a mixture of green tea polyphenols covalently lipophilized with palmitic acid through one or more of the hydroxyl groups. PP molecules have previously demonstrated enhanced bioavailability and excellent bioactivities, including antiviral, antitumor, antibacterial, and antifungal properties and were recognized as Generally recognized as Safe (GRAS) for use as a novel lipophilic antioxidant in various food products. Although significant research has focused on the biological properties of PP, there is limited information on its physical performance related to its unique chemical structure which includes hydrophilic and hydrophobic moieties. Current research explores the functionality of PP in lipid-based systems. First, the natural self-assembly of PP in edible oil was investigated where the formation of reverse nano-micelles at critical concentration of 1.4 %wt. was observed.  High concentrations, above 23 %wt., demonstrated further micelle-micelle association leading to the formation of a mesophase, thereby significantly changing the physicochemical properties of the oil. The interfacial behavior of PP, particularly its ability to adsorb at the oil-water interface supporting the formation of an emulsion, was investigated. Various water/oil ratios and PP concentrations were examined. The interfacial behavior of PP at water-oil ratio was verified using drop shape analyzer and Langmuir–Blodgett trough. Confocal microscopy images showed that PP molecules allocated at the water/oil interface, stabilizing water-in-oil (W/O) type emulsion. Furthermore, increasing the PP content induced the self-association and organization of PP within the continuous oil phase, leading to the formation of an emulsion gel. The fundamental insights gained from this study highlight PP's potential, not only as a powerful antioxidant in food products, but also as a multifunctional food additive with diverse applications.