Optimization of spray drying process parameters for kefir powder using response surface methodology

- We modeled and optimized the production of kefir powder by using spray dryer and compared with freeze dryer.
- At the optimum spray dried kefir powder had the same high-quality as the freeze dried (lyophilizied) kefir powder.
- Effect of inlet air temperature was found the main parameter that effect the survival rates of microorganisms.
- In order to get high quality food powder, optimization is a necessary step for determining the drying process parameters.
- Because of easy to use properties of kefir powder, consuming of kefir powder can be increased in the homes.

In this study response surface methodology (RSM) was used to optimize the spray drying process conditions for production of kefir powder. Influence of inlet air temperature (120-180 °C), feed temperature (4-30 °C) and pump rate (20-40%) on the survival rates of microorganisms, outlet temperature, moisture content and water activity were assessed after drying and modeled by RSM. A lab-scale spray dryer (Mini Spray Dryer B-290, Switzerland) was used to carry out the drying experiments which are planned according to Central Composite Rotatable Design (CCRD). Inlet temperature was found as the main factor that effects the all responses statistically significant (p < 0.05). Effect of pump rate on the responses was found significant for some responses. Feed temperature has no significant effect for any responses. The optimum conditions were found as 135 °C inlet air temperature and 35% pump rate with using Desirability Function. Desired parameters were determined in regard to model fit and lack of fit test analysis results. At the end of this study, optimum conditions of spray drying were matched with freeze drying results. Results showed that at the optimum point, good quality powder can be obtained as freeze dried powder quality.