Process for production of purified cane juice for sugar manufacture

Abstract

The present invention relates to a process for producing sugar from cane that includes the steps of: (a) grinding sugar cane or pieces thereof into pulp; (b) mechanically separating juice from the pulp; and (c) membrane filtering the separated juice, for example through a ultrafiltration membrane, producing a retentate and a permeate. Preferably in step (a), the cane is cut into pieces having an average fiber length of less than 10 millimeters, more preferably into pieces having an average fiber length of less than 5 mm with a fiber diameter of about 200 microns or less. The mechanical separation of juice from cane pieces can be done suitably by filtration or centrifugation. It is preferred to adjust the pH of the separated juice to at least about 7 prior to membrane filtration, more preferably to at least about 7.5, for example by adding lime or sodium hydroxide. The permeate can be evaporated and crystallized by conventional means to produce white sugar. The mother liquor from this first crystallization can be crystallized further, usually twice more and the sugar obtained can either be used directly as a product, or remelted with the feed to the first crystallization. The remaining mother liquor is molasses.