Effect of spray drying process conditions on bacteria survival and acetaldehyde retention in sweetened yoghurt powder: An optimization study

摘要

The objective of this study was to optimize the spray drying conditions in developing a sweetened yoghurt powder using response surface methodology. Results indicated that the corresponding response surface model was sufficient to describe and predict powder characteristics in terms of moisture content (% db), bacteria survival ratio (N/No), acetaldehyde retention (%), and overall sensory score with R-2 of 98.24, 98.44, 98.57, and 97.85%, respectively. Under optimal conditions (inlet air temperature 148 degrees C, feed rate 0.54 L/h, and atomization pressure 898 kPa), the response variables including the moisture content, bacteria survival ratio, acetaldehyde retention, and overall sensory score were predicted and validated as 3.69% (db), 2.37 x 10(-3), 76.39%, and 8.0, respectively. Furthermore, physicochemical properties and morphology of the optimally developed sweetened yoghurt powder were studied. It was concluded that a reasonably good-quality shelf-stable powder can be developed from sweetened yoghurt having adequate bacteria count and acetaldehyde content by spray drying.