COLOR DEGRADATION AND COALESCENCE KINETICS OF AZTEC MARIGOLD OLEORESIN-IN-WATER EMULSIONS STABILIZED BY MESQUITE OR ARABIC GUMS AND THEIR BLENDS

Aztec marigold oleoresin-in-water (O/W) emulsions were formulated with mesquite gum or gum arabic and their blends as emulsifying and protec tive agents, at pH values of 3, 5 and 7. Changes in the emulsions aver age particle size were determined by laser ray diffraction, in tinctor ial power by visible spectrophotometry and in color by reflectance mea surements. Both gums and their blends form highly stable O/W emulsions against drop coalescence and color loss. The emulsifying agent compos ition and pH have an important role in determining the degree of effec tiveness of the emulsions against color loss and drop coalescence kine tics. Mesquite gum provided a better stability against drop coalescenc e than gum arabic, and furthermore their blends had a synergistic effe ct providing a higher stability to the emulsions than either gum on it s own. With regard to the marigold oleoresin pigment degradation, mesq uite gum provided a much better protection than gum arabic or their bl ends. At pH 5 the color loss or pigment degradation was retarded longe r than at pH 3 and 7. It is assumed that the polyelectrolytic nature o f the gums and their molecular weight play an important role in the co lor protection mechanism, as well as the inherent darker color of mesq uite gum that may act as a sun-light filter.