Sugar beet membrane filtration process

A process for producing sugar from beets, comprising the steps of:

• (a) macerating sugar beets or pieces thereof, thereby forming pulp that comprises sucrose-containing aqueous liquid;
• (b) separating the sucrose-containing liquid from the pulp at a temperature of at least about 65° C.;
• (c) filtering the sucrose-containing liquid through a first ultrafiltration membrane that has a molecular weight cutoff of about 4,000-200,000 daltons, thereby producing a first ultrafiltration permeate that has a color no greater an about 10,000 icu and a first ultrafiltration retentate;
• (d) filtering the first ultrafiltration permeate through a second ultrafiltration membrane that has a molecular weight cutoff of about 2,000-4,000 daltons, thereby producing a second ultrafiltration permeate that was a color no greater than about 4,000 icu and a second ultrafiltration retentate;
• (e) filtering the second ultrafiltration permeate through a nanofiltration membrane;
• thereby producing a nanofiltration permeate and a nanofiltration retentate, wherein the nanofiltration retentate has a higher concentration of sucrose on a dry solids basis than the sucrose-containing liquid in step (b);
• (f) purifying the nanofiltration retentate by at least one method selected from the group consisting of ion exchange and electrodialysis, thereby producing an evaporator feed;
• (g) evaporating water from the evaporator feed to produce a concentrated syrup;
• and
• (h) crystallizing white sugar from the concentrated syrup.

A process for purifying a sucrose-containing juice obtained from sugar beets, comprising the steps of:

• (a) macerating sugar beets or pieces thereof, thereby forming pulp that comprises sucrose-containing aqueous liquid;
• (b) separating the sucrose-containing liquid from the pulp at a temperature of at least about 65° C.;
• (c) introducing sufficient air into the juice to cause polymerisation of color bodies;
• (d) heating the juice to a temperature of about 140-200° F.;
• and
• (e) removing at least some of the color bodies from the juice by membrane filtration through at least one ultrafiltration membrane or nanofiltration membrane.