Porosity Evaluation of Ginseng Roots from Real-Time Imaging and Mass Measurements

Real-time imaging and mass measurements were used for evaluation of instantaneous porosity in convective drying of ginseng roots. Porosity changes were evaluated from moisture–shrinkage–porosity correlation. It was found that any deviation of shrinkage–moisture relationship from linearity was due to the changes of porosity. The impact of temperature on porosity development was evaluated from drying experiments at moderate (38 °C) and high (50 °C) temperatures. Drying at 38 °C resulted in gradual increasing of porosity to 20–25% with the next quick decreasing of porosity to 10–15% at the end of drying due to intensive shrinkage. In contrast, drying at 50 °C resulted in constant porosity (0–5%) for most of the drying period, with the next increasing to 30% at the end of drying due to the case hardening. The method of porosity evaluation was verified with direct microscopic measurements at different stages of drying.