sulphur for white sugar / sulfur dioxide for sugar

Sulfur DioxideCane sugar is naturally brown because of the presence of molasses. During the drying process, raw sugar cane juice is mixed with lime and evaporated. Sulfur dioxide is added to milled white sugar before evaporation. This is what makes table sugar white. The sulfur dioxide bleaches the cane sugar. brown sugar made from date palm sap or sugarcane juice, has a as they are, can be bleached by sulfur dioxide, or can be treated in a carbonisation process to produce a whiter product. Raw sugarcane juice has a low pH value of 4 or 5 which is slightly acidic in nature. At this level, sugar gets converted into other forms, like glucose and fructose which is not desirable. To prevent this, the juice is heated to about 70 degree Celsius and a little bit of lime or calcium oxide, is added to it, which takes the pH value to around 9.5. This mixture of juice and lime is then treated with SO2 to bring the pH value to the neutral level of 7. In the process, the calcium oxide reacts with sulphur dioxide to produce sulphites and sulphates of calcium, which helps in the clarification/purification of the sugarcane juice. The mud thus formed is removed by filtration as ‘press mud’

Sulphur dioxide is used at a later stage as well, after the juice has been concentrated and is being crystallised. At this point, SO2 works as a bleaching agent and is responsible for ensuring that the end product, sugar, is white in color.