Effects of fat and dry matter content on some properties of Doogh powder produced in laboratory scale

Production and export of Doogh as a Iranian fermented national drink have increased. Contamination of Doogh by yeasts and molds is one of the defects that results in spoilage and increasing the waste of the product. Drying and convertion of Doogh to its powder by spray dryer is one of the method for increasing the shelf life and decreasing the volume and the costs of transportation. In this study Doogh samples with fat content (0.5% and 1.5%), dry matter without fat and salt (3.5% and 4.5%) and 0.7% salt were first dried in preliminary tests including inlet air temperature (100, 150 and 200 oC), liquid feed flow rate (5,10 and 15 mL min˗1) and drying air flow rate (400, 600 and 800 L h˗). Best condition were adjusted accordingto the best results of solubility test and were conducted to drying the samples. fat content and dry matter had significant effect on physical, chemical and microbial characteristics of Doogh powder. First and forth formula had highest and lowest solubility. The solubility of first and forth formula was 82.11±0.62% at 25 oC and 63.18±0.33% at 15 oC respectively. Increasing the fat content results in decreasing the solubility, increasing the particle size and the rate of viable starter counts.