Withida Chantrapornchai

Influence of relative refractive index on optical properties of emulsions

Abstract The influence of refractive index on the optical properties of 4 wt.% n -hexadecane oil-in-water emulsions with the same droplet diameter (1 μm) and refractive index ( n d =1.43), but different aqueous phase refractive index ( n aq =1.33–1.46) was examined in the absence and presence of red dye. As the n d / n aq ratio moved away from one (either higher or lower), the scattering efficiency of the emulsion droplets increased. This caused the emulsion appearance to go from transparent to opaque, with a corresponding increase in spectral reflectance, L -value and turbidity. The spectral reflectance and tristimulus values of the dyed emulsions predicted by light scattering theory were compared with measured values. The spectral reflectance and L -value predicted by the theory showed similar trends to measured spectra, but the a - and b -values showed opposite trends. Three approaches have been proposed to correct this discrepancy.

Optical properties of oil-in-water emulsions containing titanium dioxide particles

Abstract The influence of titanium dioxide particles (d32=0.62 μm, φ=0–0.3 wt%) on the spectral reflectance and tristimulus color coordinates (L, a, b) of n-hexadecane oil-in-water emulsions (d32=0.29 μm, φ=0.25–20 wt%) was measured in the absence and presence of a red dye. There was a steep decrease in the spectral reflectance and ‘lightness’ of emulsions at droplet concentrations below 3 wt% and in titanium dioxide suspensions at particle concentrations below 0.1 wt%. In the absence of dye, dilute emulsions (φ 0.3 wt%) of titanium dioxide was required to match the color of dilute emulsions to concentrated ones. There was reasonable agreement between the measured optical properties of emulsions containing titanium dioxide and those predicted by light scattering theory. These results have important consequences for optimizing the appearance of emulsion-based products with reduced droplet concentrations, e.g. low-fat foods.

Influence of Polyglycerol Polyricinoleate and Biopolymers on Physical Properties and Encapsulation Efficiency of Water-in-Oil-in-Water Emulsions Containing Mango Seed Kernel Extract

The influence of polyglycerol polyricinoleate (PGPR) and biopolymers (gelatin and sodium alginate) on the stabilization of water-in-oil (W/O) emulsions was investigated to improve the encapsulation efficiency (EE) of water-in-oil-in-water (W/O/W) emulsions containing mango seed kernel extract (MSKE). The physical properties and EE of the emulsions were found to depend more strongly on PGPR than on biopolymers. High EE values of MSKE were obtained when W/O emulsions stabilized by 4–8 wt% PGPR were incorporated with 1–5 wt% gelatin, or by 6–8 wt% PGPR incorporated with 0.5–1.5 wt% sodium alginate in the inner aqueous phase. GRAPHICAL ABSTRACT