Abstract
Application of pervaporation and osmotic membrane distillation to the regeneration of spent solutions from the osmotic food dehydration Results of pervaporation (PV) of sucrose and calcium chloride spent solutions were presented. Additionally, osmotic membrane distillation (OMD) of sucrose solutions was investigated. It was found that the regeneration of spent sucrose solution for the reuse is possible by using PV or OMD processes. However, OMD process produces another spent stream i.e. CaCl2. Pervaporation membranes showed fluxes in the range of 0.5 - 0.9 kg m-2 h-1 in contact with 40° Brix sucrose solution, whereas OMD water permeate fluxes were in the range of 4 - 5 kg m-2 h-1 for the same feed concentration. Two different hybrid processes were suggested: i) pretreatment followed by OMD reconcentration of spent sucrose solution and independently PV for CaCl2 regeneration; ii) membrane pretreatment (MP) followed by PV of sucrose solution. Based on the experimental results, the membrane areas for both systems were calculated and compared. MP-PV system seems to be a better solution for the spent mixtures management.
Highlights
For the last few decades one of the most commonly used method of preservation and storage of fruit and vegetables was thermal drying
Due to its adverse effect on the final taste, flavor and texture of the obtained product[1, 2]. This adverse influence is not observed in case of osmotic dehydration (OD), a well established method of food conservation used on a large scale in the food industry[3,4,5]
The composition of a plant material is modified through a partial water removal and an impregnation by solutes, without affecting its structural integrity (Fig. 1)
Summary
For the last few decades one of the most commonly used method of preservation and storage of fruit and vegetables was thermal drying. The present paper reports a study of two hybrid membrane systems based on pervaporation (PV) and/or OMD followed by PV applied for reconcentration of spent sugar solutions from osmotic dehydration and for reconcentration of diluted osmotic agent solution. The osmotic membrane distillation is a membrane contactor technique using a porous hydrophobic membrane, e.g. PTFE membrane[17], allowing the concentration of solutions at constant temperature under atmospheric pressure[18]. Both sides of the porous membrane are in contact with two aqueous solutions of different water activity, e.g. diluted OD spent solution and concentrated CaCl2 solution. Concentration of calcium chloride solutions was determined using complexometric titration method with EDTA solution described in the details elsewhere[21]
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