Assessment and Optimization of Bulk Density and Angle of Repose of Tea Leaves for Metering Device Using Desirability Function

The current research focuses on the estimation of bulk density and angle of repose of tea leaves at different moisture content and size and development of a mathematical model for bulk density and angle of repose using response surface methodology followed by numerical optimization of responses using desirability functions. Further work was done on the design optimization of feed hopper and metering system with bulk density and angle of repose. In tea processing, during withering and maceration process the whole leaves are subjected to size reduction, rolling, maceration, feeding and conveyance. The tea leaves are generally not uniform due to plucking standard, moisture content of the leaf and the variety. Non-uniformity in feed rate of tea leaves which will ultimately pass through the feed hopper will not only affect the cut size of the leaves but unwanted friction between CTC machine rollers will cause rise in temperature to about 60 ̊C which will ultimately affect the quality of tea by influencing its theaflavin/thearubigin (TF/TR) ratio. Practically, rise in temperature above 35 ̊C deteoriates the quality of leaf and nonuniformity in leaf cutting will affect granule formation. Bulk density and angle of repose are important physical parameters of tea leave for free flow behavior during processing. Response surface methodology was used to examine the effect of size of cut leaf and moisture content of tea leaves on the mean bulk density and mean slide angle of repose.