Drying behaviors of mint leaves in vacuum freeze drying

Abstract

In this study, the drying behaviour of mint, which is one of the medicinal plants in freeze-drying, was investigated. The products were dried at three different temperatures (40, 50, 60oC) and three different pressures (30, 50, 80 kPa) in a freeze-drying system designed as a prototype. Drying time is decreased with increasing cabin pressure. Optimal working conditions in the freeze-drying of mint leaves were determined as 30 kPa chamber pressure and 50°C drying temperature. Four thin layer drying models, namely Newton model, Tow term exponential model, Logarithmic model, and Wang and Singh model are tested to predict the drying behaviour. The Wang and Singh model has presented the best prediction that has an R2 value of 0.99687.