Effect of Hydrocolloids and Drying Conditions on Stability, Rheological and Sensory Properties of Reconstituted Yoghurt (Instant Yoghurt)

Abstract

In the present study, fresh skimmed yoghurt (total solids 10, 20, 28 %wt) was dried using microwave–vacuum drier (35, 135, and 260 Watt, absolute pressure 125 mbar). Then, the effect of this process on the survival of starters as well as yogurt powder color was investigated. Moreover, various concentrations of different hydrocolloids (tragacanth, guar, Persian, locust bean), as well as their mixtures were added, either to fresh yogurt or to yoghurt powder, in order to compare their influences on rheological and sensory properties of the reconstituted yogurt. Our findings showed that microwave power and total solids negatively affected color indices and number of survivals. In addition, adding the hydrocolloids to fresh yogurt produced more desirable sensory and rheological properties in comparison to yogurt powder. Furthermore, G’ and G”, complex viscosity and loss tangent of majority of hydrocolloid-containing reconstituted yogurts (fresh yogurt method) were similar to the fresh one, indicating dominant elastic behavior.