Application of osmotic membrane distillation for reconcentration of sugar solutions from osmotic dehydration

In the current study osmotic membrane distillation (OMD) was applied to reconcentrate osmotic dehydration spent sucrose solutions. The OMD experiments were performed at constant temperature of 35 °C, using PTFE membrane. During the experiments sucrose solutions of different concentrations (30–60 °Brix) were partially dehydrated using 50% (w/w) CaCl2 and 24.6% (w/w) NaCl as stripping solutions. CaCl2 as more efficient stripping solution was then used to reconcentrate spent solutions obtained from osmotic dehydration (OD) of apples. After experiments sucrose and reducing sugars presence in stripping solutions was analyzed and CaCl2 and NaCl presence was checked in sucrose and OD solutions. As far as feed solutions up to 60 °Brix were considered the water flux in OMD depended mainly on water activity in the stripping solution and the concentration of sucrose solution. However, for the feed solutions of 60 °Brix its viscosity was the determinant factor during the process. For OD spent solution water flux was lower due to the presence of suspended solids. Stripping solutions and sucrose solutions analysis showed that ions or sugars were retained and mainly water was transported through the membrane.