Doogh is an Iranian type of traditional fermented dairy based drink which is usually prepared by mixing water, salt, yoghurt, as well as some aqueous extracts of local herbs. Serum separation in Doogh is a major problem which happens due to low pH (≤4) and aggregation of caseins. There are many reports on the
stabilization of acidified milk drinks like a
doogh using different kinds of hydrocolloids such as gellan gum, Locust bean gum, pectin, starch, tragacanth, Carrageenan gum, Guar gum. The effects of these hydrocolloids on the stability, viscosity, particle size, zeta potential, microstructure were investigated. According to results, The addition of gum tragacanth improved stabilisation of
doogh samples which was associated with an increase in apparent viscosity and storage modulus. Furthermore, the particle size distribution showed an increase in polydispersity and a pronounced reduction in median diameter of protein–polysaccharide complexes. The soluble tragacanthin (T) is responsible for
doogh stability and insoluble tragacanthin (B) is responsible for capability of gel formation in GT owing to its high molecular weight. Furthermore, the proper rheological model for control was Newtonian whereas for the others it was Power law. Based on viscoelastic experiments, Dooghs containing hydrocolloids exhibited dominant viscose and elastic behaviors. The presence of hydrocolloids in the formulation of
doogh led to a paramount change in their zeta potential values. It is also important to note that non-adsorbing hydrocolloids such as locust bean gum or likely bassorin (B) do not have any significant influence on zeta potential as they are unable to interact with caseins. Acording to findings,
hydrocolloid additions made
doogh stable by surface adsorption on to caseins and induces
stabilization via electrostatic and steric repulsions. The microscopic images of Doogh in the presence and absence of hydrocolloids showed that caseins are in an aggregated form in control whereas the hydrocolloids prevent approaching the caseins and these particles are separated from each other The presence of hydrocolloids allows the formation of single particles as well as small clusters. Stabilization of
doogh with hydrocolloids (low concentration) had no adverse effect on organoleptic acceptability