IRON MEDIATED CLARIFICATION AND DECOLOURISATION OF SUGARCANE JUICE

By L.R. MADSEN II and D.F. DAY
Louisiana State UniversityAgricultural Center Audubon Sugar Institute, St. Gabriel, La. 70776  Lmadsen@agctr.lsu.edu

KEYWORDS: Colour, Removal, Clarification, Iron.

Abstract

IN ORDER TOoperate most profitably, the sugar producers in Louisiana wish to engage in a cooperative arrangement with the sugar refineries. Because the sugar refinery is an industrial scale decolouriser that operates using natural gas as fuel, it makes sense that sugar with less colour, produced using bagasse-power, would likely have greater profit margins. The removal of phenolic colorants from raw juice using native cane protein as a vehicle and Fe3+ as an oxidative catalyst was studied. Colour was removed as phenolprotein conjugates which rapidly precipitated with the addition of a cationic flocculant. The decanted juice was clarified via cold-liming. The treatment yielded clarified juice with up to 70% lower colour than hot-liming juice. It appears that the phenolics were oxidised by Fe3+ which engaged a REDOX cycle yielding quinoid species. The free N-ε amino groups of lysine in the albuminoid proteins appeared to add to the quinones.  Stoichiometry indicated a degree of polymerisation of eight. Oligomer formation ceased at this length which appeared sufficient to facilitate irreversiblecross-linking and/or capping of the protein. The aggregates of iron, lignol(s) and protein were insoluble and precipitated. The process was tested in a 150 L settling clarifier which was operated in both pulsed and continuous modes. The method scaled well and the product juice exhibited 50–60% less colour than a cold-limed control when Fe3+ was applied in quantities ranging from 100–200 mg/L.

Source http://www.issct.org/pdf/proceedings/2010/2010%20Madsen,%20IRON%20MEDIATED%20CLARIFICATION%20AND%20DECOLOURISATION%20OF%20SUGARCANE%20JUICE.pdf