In chemical and physical processes such as emulsification, oil/water interfaces are created very rapidly. Mass transfer mechanisms determine rates of surfactant adsorption and subsequent interfacial tension reduction, with important implications for the final product structure and formulation. However, for hydrophobic fatty acid esters commonly used to form food emulsions, these mechanisms have not been explored in depth. Therefore, the objective of our research was to investigate the transport kinetics of lipid-based amphiphiles with poor water solubility, including free fatty acids and monoglycerides, using a drop profile tensiometer.<br/><br/>Monocaprylin or caprylic acid dissolved in tricaprylin transferred rapidly to a pendant water droplet interface, steeply decreasing the interfacial tension in a diffusion-limited process. However, surfactant adsorption from inside an oil drop was complicated by oil-water partitioning and transport through multiple phases, behavior that can be understood with the aid of mass transfer theory. In commercial corn oil the behavior was still more complex. Purchased corn oil contained native components that promoted a substantial and time-dependent decrease in the interfacial tension. Fatty acid addition at low concentrations actually increased the tension, due to apparent interactions between native amphiphiles and the fatty acid. Purification using magnesium silicate removed the native amphiphiles, yielding a much higher and time-independent interfacial tension. This tension was now reduced at all concentrations by addition of the fatty acid. For the monoglyceride, possible roles of self-assembled structures in the triglyceride were also probed.<br/><br/>The complex kinetics seen in our research can be harnessed to improve processes such as oil uptake, wetting, nucleation, emulsification and detergency. Our results are of particular significance in the utilization of lipid-based amphiphiles, including those that are natural and unrestricted for their addition to food.

Mass transfer of lipid-based amphiphiles to water-triglyceride interfaces

253rd National Meeting (2017)

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