Drying of North American ginseng roots (Panax quinquefolius L.)

The roots of North American ginseng (Panax quinquefolius L.) are dried from approximately 70% to less than 10% (wet basis), during which the roots may shrink up to 50% of their initial volume. Drying and shrinkage affect the physical quality of the dried root. Samples of fresh ginseng roots were dri ed and the root shrinkage was measured. The experimental drying data were u sed to test a single-tank shrinkage model and a two-tank shrinkage model in calculating shrinkage of ginseng root. For the single-tank shrinkage model , the moisture is evenly distributed throughout the root cross section and as a result shrinkage takes place uniformly. For the two-tank drying model, the cross section of the root is divided into a moist core and a dry outer -layer. The shrinkage commences from the outer-layer moving towards the cen tral parts of the root as drying progresses. By comparing shrinkage of peel ed and un peeled samples, it was concluded that the root skin (epidermis) a cts as a major barrier against moisture efflux from the root and hence cont rols the root shrinkage.