A practical optimization on salt/high-methoxyl pectin interaction to design a stable formulation for Doogh

Doogh is a traditional Iranian fermented drink. Response surface methodology-central composite design (RSM-CCD) was used to determine optimum formulation for the production of Doogh stabilized by high methoxyl pectin (HMP). The effects of HMP (0.28-0.42% wt) and salt (0.4-1.1% wt) concentrations on the stability, viscosity, volume-weighted (D43) and surface-weighted (D32) mean diameters and Span were investigated. Graphical response surface plots were applied to locate the optimum point. The optimum composition for stable Doogh production was found to contain (% wt) HMP 0.4 and salt 0.62. These optimum conditions yielded the stability of 96.34%, viscosity of 2.05 mPa s, D43 of 11.922 μm, D32 of 0.966 μm and Span value of 2.140. There was no significant difference between the physical, rheological and sensory attributes of Dooghs produced under optimum conditions and commercial samples.