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How Cane Sugar is Refined - Affination

Affination is the key to good refining because one gets the best improvement in quality for the least capital and running cost. The mixture of syrup and raw sugar crystals is called the "magma", and rightly so because it is an extremely viscous dark brown liquid mixture not unlike the magma flowing from some volcanoes. Careful control of its temperature and liquid content are critical:

  • too much liquid leads to excessive dissolution of the relatively pure sugar crystals;
  • too little liquid and the coating will not be washed off, nor will the liquid phase spin off the crystals;
  • too low a temperature and the coating will not soften and wash off, nor will the liquid phase spin off the crystals;
  • too high a temperature and extra colour will form as sugar degrades;

Typical operating conditions would be to have the magma at about 10% water content at 70 ºC. Once the crystals are recovered they are dissolved up to make a sugar liquor of about 50% solids content for passing forward to the next stage of refining.

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