Investigating the impact of sodium alginate and xanthan hydrocolloids on the rheological Doogh properties (Iranian dairy drink)

Doogh is a traditional Iranian fermented dairy drink that has gained popularity as a low-calorie alternative to soft drinks. The incorporation of hydrocolloids like sodium alginate and xanthan gum may enhance its rheological properties and stability. This study aims to evaluate the effects of sodium alginate and xanthan gum at varying concentrations (0 %, 0.04 %, 0.07 %, and 0.1 %) on the rheological characteristics of Doogh. Doogh was prepared by diluting yogurt with water and adding double-crystallized salt, followed by the incorporation of hydrocolloids. Rheological properties were assessed using steady flow and dynamic tests over a 42-day storage period at 48 °C. Key parameters such as apparent viscosity, flow behavior index, and yield stress were measured. The addition of hydrocolloids significantly altered the rheological behavior of Doogh, shifting it from Newtonian to pseudoplastic. The highest apparent viscosity (490.18 Pa·s) was recorded in the 0.1 % hydrocolloid sample, while the control (0 %) exhibited the lowest viscosity (270.38 Pa·s). The flow index (n) values were consistently below 1, indicating non-Newtonian behavior, with the 0.1 % sample demonstrating the strongest shear-thinning effect (n = 0.510). Yield stress increased with hydrocolloid concentration, reaching 2013.608 Pa in the 0.1 % sample compared to 743.135 Pa in the control. The incorporation of sodium alginate and xanthan gum effectively enhances the stability and viscosity of Doogh without adversely affecting its rheological behavior during storage. These findings suggest that hydrocolloids can be beneficial in improving the quality of Doogh as a functional beverage.