Formation of sacha inchi oil microemulsion systems: effects of non-ionic surfactants, short-chain alcohols, straight-chain esters and essential oils

BACKGROUND This study reports the formation of sacha inchi oil (SIO) microemulsions for food and cosmetic applications. Effects of non-ionic surfactants, short-chain alcohols, essential oil and straight-chain esters on the phase behavior and formulation of U-type microemulsion were investigated. Pseudo ternary phase diagrams were constructed to assess the influence of these factors using water titration method. Structural transitions were measured along several water dilution lines using conductivity and viscosity tools. RESULTS Among four different surfactants, Tween 80 solubilized the maximum oil and induced the formation of a U-type microemulsion system. Oil solubilization was decreased in the presence of short-chain alcohols. In addition, the system containing straight-chain esters as the cosolvent showed a higher expansion effect in the U-type areas than that containing essential oils. Finally, upon water dilution of three systems with SIO/ethyl acetate of 1:1, 1:2 and 1:3, microstructural transition from W/O to bicontinuous occurred at 200 g kg(-1) (w/w) water content, and then to O/W structure at 650 g kg(-1) (w/w) water content. CONCLUSION Straight-chain esters as cosolvent is a potential strategy to extend the dilutability of SIO microemulsions. (c) 2021 Society of Chemical Industry.

Automated summary

Among the four different surfactants tested, Tween 80 was found to solubilize the maximum amount of oil and induce the formation of a U-type microemulsion system. The presence of short-chain alcohols decreased oil solubilization, while straight-chain esters as cosolvent showed a higher expansion effect in the U-type areas compared to systems containing essential oils. Structural transitions from W/O to bicontinuous and then to O/W were observed upon water dilution of the microemulsions.