Sugar cane - production & trade
South Asian production
Sugar cane yields the highest number of calories per unit area of any plant. Today, sugar cane has many industrial uses and is one of the most widely used and cheapest domestic products.
|This photograph shows a sugar cane plantation in Uttar Pradesh in about 1910. This area is still one of India's primary sugar cane producing states.|
Substantial increases in yields have occurred over the past 100 years due to improved cultivation and breeding of higher-yielding varieties.
Sugar cane plantations are usually established in the spring, by planting stem cuttings in fields. As they grow, the stems multiply at the base, often producing a cluster of 2 or 3 stems. The stems thrive in full sunshine, and as they mature the sugar content increases. Cut sugar cane re-grows, so plantations last for many years without having to replant.
Harvesting and processingStems are usually harvested at the age of about 11-14 months. The stems are usually cut manually and are bundled to be taken to a sugar mill. Canes are shredded and crushed with heavy rollers to retrieve the juice which contains 10-20% sucrose. This juice, which is dull green and murky, is sieved to filter out some of the impurities.
The vast majority of cane sugar commercially produced today is known as 'centrifugal'. With this process, the pH is raised with lime and the mixture is heated to around 100 degrees centigrade for several hours. The lime causes suspended materials, proteins, waxes, and fats to separate out. Further impurities are allowed to settle in large containers and are removed from the bottom. This residue is known as filter-cake or press-mud. The clear juice is evaporated off to form crystals. Sugar crystals are separated from the molasses, or brown syrup, by centrifugation. The sugar produced in raw, and brown specialties are demerara and muscovado.
This raw brown sugar can be refined to produce white sugar, whch is almost 100 per cent sucrose. This usually happens in the country of import. Icing sugar is manufactured by pulverising refined sugar in a mill. It is mostly used for confectionery and for cakes, pastries and other baked products.
Non-centrifugal sugars include gur. Here sugar cane juice is heated over an open fire to give a thick, paste-like product.
Molasses is a by-product of the manufacturing of cane sugar. It is a residual syrup from which no more crystalline sucrose can be obtained by simple techniques.