Sugar Decolorization


The sugar origin comes from the ancient world, about 8,000 years ago when it was introduced in the Indian culture as a garden plant for chewing purposes. The plant name was Śarkarā. Later in history, the Chinese, Greek, Roman, and Persian cultures had cultivated and used the plant for centuries. However, the first evidence of the use of crystallized sugar comes from ancient Persia, circa 500 A.D., and due to the Arabic control of North Africa, the Europeans, rediscover the sugar in the middle ages, especially in Spain, where the Arabs were ruling for approximated 711 years. The Arabic name for crystallized sugar was Assúkkar, from there the Spanish name, Azúcar, the English name, Sugar, and the German name of Zucker.

Chemically, sugar by definition is a disaccharide called sucrose, it has no color in its pure state, 99.999%, its molecular formula is C12H22O11, and is composed of two monosaccharides, Glucose (C6H12O6) and Fructose (C6H12O6). Sugar is synthesized, naturally by plants through photosynthesis. The higher sugar content fruits in nature are bananas (18-22%), sugar cane (8 – 16%), and sugar beet (10-18%).

Sugar production

The sugar industrial production and manufacturing is a complex process that has evolved throughout the last 1,500 years. From the simple ancient process of crushing the sugar cane and cook the obtained juice until evaporation to get raw sugar crystals, with very low productivity, less than 1 kg per metric ton to the actual average of 106 – 120 kg per metric ton.

The sugar industrial process starts with the milling where the sugar cane is crushed producing a juice, called “Thin Juice”, which due to the high content of sugar and pollutant agents is required to add chemical biocides to delay sucrose content decay. After this process, sugar juice is neutralized (pH 6 – 7), with lime to flocculate and precipitate sediments and fibers (alkaline pH is linked with color formation).

The clarified and neutralized thin juice, with initially 8 ̊Bx (Unit of sugar content) is evaporated to concentrate it to 60-65 ̊ Bx. Later on, in the raw sugar cooking process, it will be seeded with sugar crystals to promote raw sugar crystallization. The crystallized sugar is centrifuged to separate its water content, obtaining in this way raw sugar with a 96 – 98% purity and color content between 600 to 4,000 ICUMSA (Sugar color measurement unit).

Raw sugar has limited industrial applications, therefore it requires to be refined to bring it to the required industrial standards, 99.96% purity and color < 25 ICUMSA.

To refine the raw sugar and increase its purity it is necessary to remelt it, clarify it, filtrate, and traditionally adding decolorating agents such as powder bone char, polymers, hydrogen peroxide, and/or sulfites.

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