Colorants
- Present naturally in cane juice :
- Chlorophyll, xanthophylls, carotene and anthocyanine.
- Developed during processing due to changes in pH temperature and retention time :
- caramalization, decomposition of reducing sugars and reaction of RS with amino acids.
- Polyphenols like tannins / saccharetine forms color during processing are present naturally in cane.
Bagacillo – Major color carrier
- Improvements in milling technology and higher cane preparation led to carry over of bagacillo and pith to juice.
- 1% bagacillo in MJ increases clear juice color by 2.5 %
- Bagacillo is around 50% cellulose and rest hemicelluloses, pentosans and lignin.
- Hemicelluloses has pentose,
- lignin has saccharetin.
- Originally colorless but forms yellow color with MOL treatment.
- Reacts with iron and oxygen under alkaline conditions forms dark colored compounds.
ICUMSA Color of sugar : colloidal impurities.
- Colloidal impurities affecting ICUMSA color
- Bagacillo in mixed juice,
- Bagacillo and pith in rotary vacuum filtrate
- Fine girt, sand, silica and un-dissolved particles in milk of lime (MOL)
- Fine sugar crystals in melt.
Effect of colloidal impurities :
- Higher lime and sulfur consumption.
- Improper heat exchange.
- Increased pan boiling time.
- Increased viscosity.
- Poor exhaustion of molasses.
- Lower crushing rate.
- Poor sugar quality wrt color, ash, SPM & RS.
Prevention is better than cure-
- Filtration can prevent the entry of these suspended colloidal matter. This can be achieved by screening of inputs.
- DSM screens with 0.7 mm aperture.
- Insufficient to separate fine bagacillo.
- Double DSM screens with 0.5 / 0.3 mm aperture in series.
- Chocking of screens reduces efficiency.
- Rotary screens could not solve chocking problems.
Special Device is necessary to :
- Avoid screen blinding,
- Removal of suspended impurities / fine bagacillo,
- Minimum retention time,
- Minimum water, steam and power consumption
