The evaluation of the performance of an experimental apparatus for the determination of flour sorption isotherms was carried out. To adjust the water activity - Aa - values (0.51; 0.57; 0.67; 0.75; 0.79 and 0.81) of the air stream, saturated salt solutions were used. The comparison of the apparatus with and without air recycling, was done by determining the sorption isotherm of soybean flour at 35°C. The air recycling model enables to obtain reliable data in a high Aa range, where samples are usually impaired by microbial growth when the other model is used. Time to obtain equilibrium for soybean flour with the air recycling model was about 50% less than for the model without air recycling.
sorption isotherm; water activity; soybean flour
