Water desorption isotherm and drying characteristics of green soybean

• Desorption isotherm of green soybeans was determined and it was belong to Type III.
• Drying characteristics of green soybean seeds were determined.
• Page model gave best fitting to the data of thin layer drying of green soybeans.
• Net isosteric heat of water desorption was calculated.

There is very little published information on green soybean about moisture sorption and drying. Water desorption isotherms were determined by the static gravimetric method using saturated salt solutions at 20, 30, and 40 °C. By comparing the index of goodness of fit, the isotherm for green soybean seeds could be better described by the Halsey equation with the desorption isotherm parameters A and B estimated to be 5.612 and 1.538 respectively. The net isosteric heat of water desorption calculated by Clausius–Clapeyron equation was from 208.8 to 3627.9 kJ/kg. Thin layer drying of green soybean seeds in a range of 25–45 °C and relative humidity from 0.2 to 0.4 dec were carried out with a heat pump dryer. The Page model was the most suitable model for describing the thin layer drying process of green soybean seeds compared with the Lewis, Henderson and Thompson models. The drying characteristics of green soybean seeds were tested and analyzed under various temperature and humidity conditions, and the results will be useful for the drying and storage of green soybean seeds.