Effect of two types of Iranian gum tragacanth on stability and rheological properties of oil-in-water emulsion

The mechanism of stabilization of oil-in-water emulsions using natural biopolymers has been a focus of many studies. The present study emphasized the importance of using native sources or a mixture of natural biopolymers as a substitute for small molecule surfactants. It also determined the effects of different concentrations of two types of Iranian gum tragacanth on the stability، rheological properties، particle size، and interfacial tension of oil-in-water emulsions. The emulsion stability of four concentrations (0. 2%، 0. 3%، 0. 4%، 5/0 w/w) of two types of gum tragacanth (Astragalus gossypinus and Astragalus fluccosus) was measured using emulsion stability tests. Then، to find and monitor the mechanism of stabilization، the rheological properties of the emulsions were measured using a rheometer immediately after production and 35 d after production at 25○C. Particle size distribution was determined using laser diffractometry and interfacial tension was measured using a tensiometer. The results showed that flow behavior parameters، particle size، and interfacial tension parameters were significantly affected by the concentration of gum tragacanth. The severity of this effect was influenced by the type of gum. Based on stability index data، samples containing only 5. 0% A. gossypinus showed higher stability than for the other concentrations. The use of appropriate types and concentrations of gum for oil-in-water emulsions can improve the stability of samples by affecting the physical and physicochemical properties of this model system.