What makes sugar white?

By Beryn Adams, Technical Marketing Manager, Asia Pacific of Liquid Purification Technologies (LPT) business unit, LANXESS

BEGINNING its journey as a naturally yellow-brown or brown tinted raw solution that is extracted from sugar beet pulp or sugarcane, white sugar undergoes a series of processes before reaching us in its universally popular white granulated form. The brownish colouration of the sugar solution increases during processing as a result of enzyme-catalysed[1] and heat-induced procedures - including maillard[2] reaction between sugar and amino acids, enzymatic browning, caramelisation and alkaline decomposition of sugars.

Highly customised ion exchange resins such as the Lewatit range from speciality chemical maker, LANXESS, enables the industrial sugar production industry to meet the tough colour intensity and other quality criteria set out by the global food and beverage industry. These specialised resins have numerous applications during the entire process of creating pure-white granulated sugar ranging from desalination and decolourisation of sugar solutions, the inversion (hydrolysis) of disaccharides[3], particularly saccharose (table sugar), and for the treatment of diluted sugary solutions. Lewatit can be used to desalinate whey, grape must and fruit juices or to remove unwanted, excess acid and bitterness from orange juice.
Decolourisation with ion exchange resins complements traditional purification methods like crystallisation, clarification through carbonatation and phosphatation, where there is affination[4] of impurities from the crystal pulp (magma).

Both mono and special heterodisperse (collision of particles of difference sizes) resins are used in the sugar decolourisation process. If the latter exhibit a low proportion of fine grain, they are also suitable for filtering concentrated and, therefore, high-viscosity solutions, i.e. syrups. This property is present with monodisperse (particles of uniform size in a dispersed phase) resins, enabling them to be regenerated more efficiently. This is reflected in both the amount of time and water required by this process. Thanks to the standardised length of diffusion paths, despite their high porosity, monodisperse resins require around 30% less water for cleaning after the actual regeneration process.

Lewatit’s macroporous ion exchange resins based primarily on styrene polymers and cross linked via divinylbenzene units comply with food law requirements of many countries around world. Lewatit act as absorbers to efficiently bind colour impurities, removing them from the sugar solutions. Absorber resins are superior to traditional activated carbon filters, particularly for solutions with only moderate colouring (< 1,000 ICU).
Not only is it far more time-consuming to regenerate these carbon filters, the regeneration process usually cannot be performed on-site, thus incurring extra cost and reducing the system’s productivity. In contrast, ion exchange resins charged with colouring molecules can quickly be readied for operation over and over again by simply washing them with a saline solution on-site, allowing enhanced operational efficiency.

Lewatit ion exchange resins help realise higher sugar yields, cut waste and meet the increasingly strict quality requirements of the food industry. The long service life of the resins and their simple and cost-effective regeneration enables their profitable application in the sugar refining process. In summary, Lewatit ion exchange resins sweeten the sugar making process by complementing and extending the process portfolio for industrial sugar production.