Iron Mediated Precipitation of Phenol:Protein Aggregates from Sugar Cane Juice

• Main Author: Madsen II, Lee R.
• Other Authors: William H. Daly
• Format: Others
• Language: en
• Published: LSU 2009
• Subjects: Chemistry
• Online Access: http://etd.lsu.edu/docs/available/etd-04082009-143703/

The Louisiana cane sugar industry is moving toward a vertically integrated arrangement where raw sugar producers will have an interest in refining. In the sugar refining process, raw sugar is affined to remove ~50 % of the color. The new refinery that will be built in Louisiana, however, will not include affining stations. To reduce costs of refining, either affining stations will need to be installed at each mill or new technologies that provide equivalent color reduction (~50% or ~750 IU) need to be implemented. As part of this dissertation a new technology for color reduction at raw sugar mills is introduced. Color in raw sugar juice was assessed using chromatography, mass spectrometry, spectroscopy (UV-VIS, FTIR) and wet chemical means. The colored materials were phenolic and conformed with the lignin-monomer classes. It was found that this color can be removed from raw juice by applying Fe3+ and cationic polyacrylamide at ambient temperature and settling. The decanted juice was clarified via cold-liming. This is a novel, inexpensive method, which yielded clarified juice with up to 70% less color than that provided using the hot-liming method. Using modeled juice, it was found that protein, dihydroxybenzoic or propenoic acids, carboxylic acid salts, and Fe3+ were required for color removal. The optimum quantities of each component conformed with the average composition of cane juice. It was hypothesized that the phenolics were oxidized by the iron, engaging in a REDOX cycle which led to oligomerization. Stoichiometry indicated a degree of polymerization of ~8. Oligomerization ceased at this length which appeared sufficient to facilitate cross-linking and/or capping of the protein. The aggregates of iron, lignol(s) and protein were insoluble and precipitated. The method was tested at pilot-scale using a 151 L (40 gal.) settling clarifier which was operated in pulsed and continuous (7.6 L/min, ~2 gpm) modes. The method scaled well and the product juice exhibited 50-60% less color than a cold-limed control when Fe3+ was applied in quantities ranging from 100-200 Ýg/mL. Cationic flocculants increased the settling rates.