The solubilization of carvacrol, a natural antimicrobial molecule, into the water-rich phases of food products allows for enhanced food preservation. However, carvacrol has poor solubility in water and thus requires encapsulation in oil-based nanoemulsion droplets. The interfacial rheological properties of oil-water fluid interfaces stabilized by lecithin or Tween 20 and in contact with carvacrol were studied using static and dynamic pendant drop tensiometry. The multiphase systems consisted of an aqueous drop containing 0.5 wt.% Ultralec soy lecithin or Tween 20 surrounded by a continuous phase of medium chain triglyceride (MCT) oil mixed with carvacrol (ratios of 100-0, 80-20, 60-40, and 50-50 by mass). Equilibrium interfacial tension was measured for each multiphase system. Oscillatory experiments were then performed of the equilibrated drops to quantify the dilatational viscoelastic response of the drop's interface by measuring the elastic storage modulus (E') and viscous loss modulus (E'') as a function of sinusoidal perturbations to the drop volume at a given frequency (0.01 to 1 Hz).Results from oscillatory experiments showed that the lecithin/pure MCT oil system displayed a relatively strong elastic response with E' > E'', where E' = 27 and E'' = 11 mN-m-1. Interestingly, the incorporation of carvacrol into the MCT oil caused a significant reduction in the elastic response of the lecithin-stabilized interface and a transition to viscous behavior with E'' > E' (e.g., E'' = 21 and E' = 9 mN-m-1 for 50-50 MCT-carvacrol mixture). Similar behavior was also observed for Tween 20, but the magnitude of the elastic response was reduced compared with the lecithin-stabilized interfaces. This transition from elastic interfaces to viscous ones in the presence of carvacrol is expected to reduce the stability of lecithin-stabilized emulsions. With this new knowledge, lecithin-stabilized nanoemulsions can be more rationally designed for the specific purpose of encapsulating and solubilizing carvacrol.

Interfacial rheological study of carvacrol encapsulation using oil-water emulsions stabilized by lecithin and Tween-20

248th National Meeting (2014)

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