Testing of a convection type cylindrical dryer for production of instant soy-dosa mix

A convection type cylindrical dryer developed was evaluated for drying of soy-cereal blended slurry to get instant soy-dosa mix. Blanched soybean splits (10 and 20%) were used in combinations with rice and blackgram. Three ingredients were mixed in given proportions, soaked for 4 h and ground using a wet grinder. The mix was then kept for about 20 h for its natural fermentation followed by drying. For drying, three temperatures were used viz. 40,50 and 60°C. The observations were recorded on moisture content of the drying product, temperature of the Inlet and outlet air, velocity of the air with and without load on the dryer at time intervals of 3 h to 18 h. The physical properties of instant soy-dosa mix such as colour, water absorption index and moisture were determined for each of the considered combinations. A control was maintained with zero proportion of soybean for comparison of results. Results indicated that the instant soy-dosa mix could be successfully dried using the developed slurry dryer for a duration of 12 h. The product obtained was utilized for production of good quality instant soy-dosa. The drying temperature of 60°C and incorporation of soybean up to 10% were found to be optimum from the view point of consumer acceptability as well as the ease of preparaton of the end product. Un melange riz-haricot mungo-soja est mis a trempe et moulu, puis maintenu pour fermentation et seche. Un secheur cylindrique a convection a ete mis au point et est teste sur ce produit. Les proprietes physico-chimiques du melange instantane obtenu soja-dosa sont etudiees. La temperature de sechage optimale est 60°, l'incorporation de soja ideale est 10%, du point de vue acceptabilite et facilite de preparation.