INVESTIGATING THE IMPACT OF FEED RATE ON THE SPRAY DRYING PROCESS OF ACHA (DIGITARIA EXILIS) SOURDOUGH

Abstract: Acha (Digitaria exilis) is a cereal crop, rich in carbohydrates, dietary fibre, minerals, and amino acids. Acha sourdough in powder form has several advantages including longer shelf life, constant product quality, and low cost of maintenance and transportation. This study aims to investigate the impact of feed rate on the spray drying process of acha (Digitaria exilis) sourdough into powder form. A fresh acha sourdough was prepared and spray-dried into powder at different feed pump rates (3, 3.5. 4, 4.5, and 5 Hz). Performance indicators of the process were analyzed. The spray dryer exit air temperature ranged from 70 ℃ to 55℃, while the relative humidity varied from 7% to 21%. The thermal efficiency and evaporation rate ranged from about 67% to 79% and 4.5 g/min to 13.0 g/min respectively. Powder yield and moisture, respectively varied from 45% to 50% and 8 % to 5%. The maximum powder yield of 50% was achieved at a feed pump rate of 4Hz. The viability of Lactic acid bacteria and yeast ranged from about 4.9 log (CFU/g) to 6 log (CFU/g) and 4.6 log (CFU/g) to 5.8 log (CFU/g) respectively. The total titrable acid ranges from 1.5 ml to 1.6 ml, while the pH varied from 4.3 to 4.2. The bulk density varied from about 4.6 g/ml to 6.0 g/ml. The results showed that the spray-drying approach produced stable sourdough powder with standard functional properties for production of gluten-free baked foods.