MASS-TRANSFER KINETICS OF OSMOTIC DEHYDRATION OF MUSHROOMS

A continuously circulated contacting reactor was designed and used for the osmotic process. Mushrooms were treated in two ways: (1) Sliced mushrooms were blanched and osmotically processed in 5, 10 and 15% salt solutions for 5, 10, 20 and 30 min at room temperature (called type 1 mushrooms); (2) Sliced and blanched mushrooms were osmotically dehydrated in 60% sucrose solution for 10 min at 50C and then transferred to the same processing conditions as mentioned in (1) (called type 2 mushrooms). The moisture content, sodium chloride and sucrose concentrations for both types of mushrooms were monitored with time. A mathematical model was used to describe the mass transfer kinetics for the two types of mushrooms. Contour plots of the mass changes in water and solutes were obtained and compared. The rates of mass changes were also determined. It was found that processing in a 15% salt solution results in the greatest ratio of rate moisture change to rate salt change for both type 1 and type 2 mushrooms. It is also the optimum condition for moisture removal and salt loading. The process method for type 2 mushroom was found the best in controlling sodium chloride penetration.