Emulsion properties of Asafoetida gum: Effect of oil concentration on stability and rheological properties

Solutions of Asafoetida gum (2% w/w) were used to prepare oil in water emulsion with various oil/gum solution ratios (0.5, 1.0, 2.0, 3.0 and 4.0 v/v). Stability and rheological properties of the emulsions were examined over 28 days of storage at 20 degrees C. It was revealed that increasing oil volume fraction enhanced the emulsion stability. The results of creaming test showed that emulsions containing oil/gum solution ratio of more than 2.0 (v/v) displayed suitable emulsion stability. Droplet size measurements and microscopic images were representative of flocculation and coalescence with increasing oil volume fraction and time of storage. Emulsion droplet size was increased from 11.11 +/- 0.99 mu m to 64.01 +/- 0.47 mu m by increasing oil/gum solution from 0.5 to 4.0. Viscosity got higher values with increasing in oil volume fraction but reduced during the storage time. According to Herschel-Bulkely model, shear thinning behavior was determined for all emulsion samples.