Rheological behavior of reconstituted yoghurt powder—An optimization study

The rheological behavior of reconstituted yoghurt powder was investigated using a numerical optimization approach. The maximum values of the rheological properties, apparent viscosity (mPa s) and consistency in the mouth were targeted as responses together with acceptable moisture content and the maximum survival ratio of the lactic acid bacteria from a previous study [1] to prevent any conflict. It was determined that the air inlet, outlet, and feed temperatures of 170, 61, and 17 °C, were the optimum processing conditions, with a predicted apparent viscosity of 1160.5 mPa s. The yoghurt powder produced at the optimum condition (± 1 °C) was reconstituted to different dry matter contents (14, 20, 25, and 30% DM) and subjected to measurements of apparent viscosity and sensorial analysis (consistency in the mouth). The consistency value of the fresh stirred yoghurt corresponded to that of the reconstituted yoghurt between 25 and 30% DM. Also, the thixotropic behavior was observed for the reconstituted yoghurt.