The Influence of Inlet Air Temperature on Spray Drying Performance: A Study on Acha (Digitaria exilis) Sourdough Dehydration

Spray drying is an effective way to dehydrate sourdough and extend its shelf life. The quality of the spray-dried product is a function of the process parameters. Therefore, this study aims to investigate the effect of different inlet air temperatures (120-180on the performance of a spray dryer used for acha (Digitaria exilis) sourdough production. The findings showed that the outlet temperature increased with an increase in inlet air temperature while the relative humidity reduced. Thermal efficiency increased with an increase, in the inlet air temperature but leveled off for temperatures above 135. The maximum efficiency was about 76% at 135 inlet air temperature. The powder yield increases with an increase in inlet air temperature, reaching about 50% but reduces with further temperature increase. The minimum moisture content was about 3.7% at an inlet air temperature of 180. Inlet air temperature variation did not cause much difference in the evaporation rate. It varied from about 9.3 to about 9.4 g/min. The total titratable acids (TTA) increased with the increase in temperature of the inlet air. The maximum TTA was 1.7ml at inlet air temperature of 180. The pH did not vary much with an increase in inlet air temperature. It ranged from about 4.16 to 4.3. The microbial survival rate reduces with an increase in inlet air temperature. The maximum cell survival was recorded at 120 It was about 62% for LAB and 59% for yeast. The bulk density varied from 0.47 to 0.58 g/ml.