Common Names: Sugarcane, sugar cane
Other Species: S. arundinaceum, S. barberi, S. bengalense (AKA - S. munja), S. edule, S. procerum, S. ravennae, S. robustum, S. sinense, S. spontaneum
Sugarcane is a tropical grass native to southeast Asia that can grow from 4-5 meters tall. It belongs to the Poaceae ("true grasses") family and, like bamboo, it has hard, jointed stalks (canes), and long, strap-like leaves with parallel veins. Its many, small wind-pollinated flowers grow in a large, feathery tuft on a single reed high above the leaves.
When harvesting sugarcane, only the stalk is cut, but the roots are left intact so that the stalk can grow back to be re-harvested for several years before they become too old to produce enough sugar and have to be replaced by new plants.
Chemistry and Processing
The cane (stem) of the sugarcane plant is harvested and its juice is processed to make crystals of brown sugar and white refined table sugar.
To make white granulated sugar (sucrose), the stalks are shredded up and their juice (which contains raw sugar) is squeezed out, treated with Ca(OH)2 (calcium hydroxide or "hydrated lime") and bubbled carbon dioxide, and then filtered to remove impurities (such as fibers and soil). This "clarified" filtered liquid is then evaporated to make it thicker before it is sent to a boiler. "Seed crystals" of sugar are added to the boiling liquid to encourage the already-present sugar crystals to grow. This liquid becomes what is called the "mother liquor," a solution that contains molasses and sugar crystals, which is then centrifuged (spun very fast, similar to a washing machine's spin cycle) to separate the molasses from the raw sugar. Once the molasses is removed, the remaining liquid is dried so that only the raw sugar crystals remain. Since there is still a brown coating of molasses on the white sugar crystals, this has to be removed by melting the raw sugar and washing this syrup by running it through a filter, the sugar is then clarified further and "decolored" with H3PO4 (phosphoric acid) and Ca(OH)2 (calcium hydroxide) or CaO (calcium oxide). Lastly, this solution is boiled again until the pure white sugar crystals are concentrated. The white crystals are then dried in a granulator and then driven through a series of screens to break up the large crystals into smaller crystals. These small, even-sized granulated crystals are the final product: white table sugar!
Other products that come from sugar cane, other than brown and white cane sugar, are: molasses, cane syrup, and wax. Sugarcane juice can also be fermented to make liquors, such as rum.
Sugar from sugar cane is used to sweeten pretty much anything from tea, to candies and desserts, to medicines. It is also used to preserve fruits and meats, to caramelize and glaze meats and vegetables, and is found in many condiments, including: barbecue sauce, ketchup, and salad dressings.
LINKS FOR MORE INFORMATION:
KEW Royal Botanic Gardens
Purdue University: Center for New Crops and Plant Products
Sugar.Org: How We Get Sugar
Canadian Sugar Institute: Sugar from Field to Table