Kinetic and thermodynamic stability of paprika nanoemulsions.

In this study, oil-in-water nanoemulsions of paprika oleoresin were prepared by high-power ultrasound. The influence of hydrophilic lipophilic balance (HLB) value and surfactant concentration on the physical and chemical stability and kinetic and thermodynamic properties were investigated. Kinetic data for thermal degradation of red and yellow fractions of carotenoids in nanoemulsions at 25, 35 and 45 °C of storage were used for estimating entropy and enthalpy of activation using the transition state theory. The mean diameters ( Z-average) of the dispersed particles containing paprika ranged from 48 to 250 nm. The carotenoids in nanoemulsions stability increased as the particle size and HLB value decreased. According to the enthalpy-entropy compensation, the carotenoid red fraction was enthalpy driven, whereas the carotenoid yellow fraction was entropy controlled. These results provide useful information for the design of delivery systems to encapsulate and stabilise lipophilic molecules. [ABSTRACT FROM AUTHOR]