Scrutinizing the different pectin types on stability of an Iranian traditional drink "Doogh"

Doogh is a fermented dairy drink which is highly consumed by Iranian people. Stability of this healthy drink was investigated in terms of sedimentation rate, viscosity, density and particle size characteristics including surface-weighted mean diameter (D32), Span and particle uniformity. Eight treatments were performed as randomized complete block design (RCBD) with three replications. Three types of pectin (high methoxyl pectin (HMP), grapefruit-seed extract pectin (GSEP) and amidated pectin (Ceamsa pectin (CSP)) at a constant concentration (0.35%w/w), three levels of salt (0.50, 0.75 and 1.00%w/w) and two dry matter contents (DMCs, 4 and 5% w/w) were used to produce the Dooghs. The results showed that the maximum stability and viscosity, and the minimum D32 were obtained by application of CSP, GSEP and HMP, respectively (p<0.05). Pectin type had no significant difference on the density values of Dooghs. The lowest sedimentation rate, viscosity, density and D32 were achieved in the minimum concentrations of salt and dry matter. The ANOVA analysis also revealed that the interaction of pectin type, salt concentration and DMC had a significant effect on the Span and particle uniformity. A maximum physical stability was found for the prepared samples with 0.35%w/w CSP, 0.5%w/w salt and 4%w/w dry matter. Evaluation of sensory attributes also confirmed that this formulation had the highest overall acceptability value.