Afg. Bailey et al., The effect of ultrafiltration on the subsequent concentration of grape juice by osmotic distillation, J MEMBR SCI, 164(1-2), 2000, pp. 195-204
The potential for osmotic distillation flux enhancement in grape juice conc
entration by ultrafiltration pretreatment has been investigated using ultra
filtration membranes with a range of pore diameter/MWCO values. Juice visco
sities were determined over the concentration range to assist with interpre
tation of the flux data. Ultrafiltration using membranes with pore diameter
s of 0.1 mu m or less resulted in appreciable osmotic distillation flux inc
reases over that observed for juice not subjected to ultrafiltration. These
flux increases have been attributed to a reduction in the viscosity of the
concentrated juice-membrane boundary layer as the result of protein remova
l. HPLC measurements showed that the normal concentration of fermentable su
gars in standard 68 degrees Brix concentrate can be achieved at a lower Bri
x value with UF permeate, thereby providing a possible means of reducing th
e handling of highly viscous streams. Ultrafiltration also resulted in an i
ncrease in juice surface tension with a consequent reduction in the tendenc
y for membrane wet-out to occur. (C) 2000 Elsevier Science B.V. All rights
reserved.