2.2.2. Osmotic evaporation
Osmotic evaporation was carried out in batch mode in a lab
scale system consisted by two independent circuits, one for the
juice and the other for the brine. The hydrophobic flat sheet membrane
(Pall Gelman – TF 200) with effective surface area of
0.032 m2 was located in the middle of a stainless steel cell
(Fig. 2). This membrane is composed by a thin polytetrafluoroethylene
selective layer supported by a polypropylene macro porous
layer. According to the manufacturer, its average characteristics
are 60% porosity, 0.2 lm average pore diameter and 165 lm thickness.
Approximately one liter of 5.5 M CaCl2 solution was used as
brine. The brine and the pre-concentrated juice were kept at
20 C and 35 C using thermostatic baths, with maximum transmembrane
pressure of 0.2 bar in order to avoid aqueous linkages
through the membrane. During osmotic evaporation, the brine
and the juice were kept under circulation at a flow rate of approximately
80 kg h1 and CaCl2 crystals were added to maintain the
brine solution near saturation (at 5.5 mol L1).