This work examines the purification of sugarcane juice in a crossflow ultra
filtration (UF) system. Experiments were conducted on-site at a sugar mill
using fresh feed drawn from the appropriate stage in the sugar manufacturin
g process. Different polymeric membranes with a nominal molecular weight cu
toff rating in the 10-50 kD range were evaluated. The 20 kD polyethersulpho
ne membrane was identified to be the most effective in terms of acceptable
flux coupled with significant removal of nonsugar impurities. Subsequent tr
ials were performed on four feed streams viz. mixed juice, raw juice, rotar
y vacuum filtrate, and clarified juice. It was observed that with the excep
tion of the clarified juice, the fine suspended particles (bagacillo) in al
l the other streams formed a secondary filtration layer on the membrane sur
face during the course of filtration. The permeate displayed a 1.5-3 unit r
ise in juice purity, which is a remarkable improvement over the 0.5-1 unit
rise obtained in the liming-sulphitation process. In addition, the UF perme
ate was typically over three times as clear with a fivefold color reduction
when compared to the clarified juice produced by the conventional process.