Rotary drying for threshing petals from marigold flowers

A rotary dryer was studied for drying and threshing petals from whole marig old flowers to obtain a petal material of relatively high xanthophyll conce ntration. Threshing efficiency varied from 70 to 90% for two of the three h arvest dates while threshing rates varied considerably. The majority of thr eshing occurred when the petal moisture content declined to below 12% w.b. A greater moisture content differential exists between unthreshed petals an d receptacles for drying temperatures of 71 degrees C than for 60 degrees C . Xanthophyll content declined with the length of time in the dryer and xan thophyll content for 71 degrees C temperature drying was lower than for 60 degrees C for the same drying time. Volume shrinkage of marigold flowers du ring drying was large. Flowers with unthreshed petal moisture contents belo w 12% w.b. occupied approximately 25% of their original volume.