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Sugarcane

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Sugarcane
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Sugar_cane_leaves.jpg
Sugar cane leaves


Scientific classification
Kingdom:Plantae
Division:Magnoliophyta
Class:Liliopsida
Order:Cyperales
Family:Poaceae
Genus:Saccharum
Species

S. spontaneum -wild
S. robustum -wild
S. officinarum -cultivated
S. barberi -cultivated
S. sinense -cultivated
S. edule -cultivated
Ref: ITIS 42058 (http://www.itis.usda.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=42058)
as of 2004-05-05

Sugarcane is one of six species of a tall tropical southeast Asian grass (Family Poaceae) having stout fibrous jointed stalks whose sap at one time was the primary source of sugar. Sugar cane is composed of six species of the genus Saccharum in tribe Andropogoneae (see taxobox). The cultivated species are complicated hybrids and all species interbreed.

Over 100 countries grow sugar cane. There are 130,000 km² (32 million acres) of sugar cane plantations worldwide. The top twenty producing countries harvested 1200 million metric tons of sugar cane in 2002 (more than 6 times the amount of sugar beet produced).[1] (http://www.fao.org/es/ess/top/commodity.jsp?lang=EN&commodity=156&CommodityList=156&year=2002&yearLyst=2002) The largest producers are Brazil, India and China.

The history of sugar in the West is an important subject for understanding the emerging industrial power of Europe in the 1700s and 1800s. Sugar cane was grown extensively in the Caribbean and still is on some islands. In colonial times sugar was a major product of the triangular trade of New World raw materials, European manufactures and African slaves. France found its sugar cane islands so valuable it effectively traded Canada to Britain for their return at the end of the Seven Years War. The Dutch similarly kept Suriname, a sugar colony in South America instead of seeking the return of the New Netherlands (New Amsterdam). Cuban sugar cane produced sugar which received price supports from and a guaranteed market in the USSR; the dissolution of that country forced the closure of most of Cuba's sugar industry. Sugar cane is still a large part of the economy in Barbados, the Dominican Republic, Guadeloupe, Jamaica, Grenada and other islands. The sugar cane industry is a major export for the Caribbean but is expected to collapse with the removal of European preferences by 2008.

Sugar cane production also greatly influenced the "modern" history of many tropical Pacific islands, most particulary the Hawaiian Islands and Fiji. In these islands, it was sugar that came to dominate the economic and political landscape after the indigenous societies were invaded by Europeans and Americans who promoted immigration of workers from various Asian countries to tend and harvest the crop. Sugar-industry policies eventually established the ethnic makeup of the island populations that now exist, thus having a profound impact on modern politics and society in the islands.

Brazil is a major grower of sugar cane where it is used to produce sugar as well as to provide the alcohol used in making gasohol and biodiesel fuels.

Contents

Cultivation

Sugarcane is native to New Guinea. Its culture requires a tropical or subtropical climate, with a minimum of 60 cm (24 in) of annual moisture. It is one of the most efficient photosynthsizers in the plant kingdom, able to convert as much as 2% of incident solar energy into biomass. In prime growing regions, such as Hawaii, sugarcane harvests can exceed 200 metric tons per hectare.

Sugarcane is propagated from cuttings, rather than from seed. Each cutting must contain at least one bud, and the cuttings are usually planted by hand. Once planted, a stand of cane can be harvested several times; after each harvest, the cane sends up new stalks, called ratoons. Usually, each successive harvest gives a smaller yield, and eventually the declining yields justify replanting. Depending on agricultural practice, 2–10 harvests may intervene between each planting.

Sugarcane is harvested either by hand or mechanically. Hand harvesting accounts for more than half of the world's sugarcane production, and is especially dominant in the developing world. When harvested by hand, the field is first set on fire. The fire spreads very rapidly, burning away the leaves, but leaving the water-rich stalks and roots unharmed. Harvesters then cut the standing cane just above the ground with knives. A skilled cane harvester can cut 500 kg of sugarcane in an hour.

The sugarcane combine, or chopper harvester, is a harvesting machine originally developed in Australia. The combine cuts the cane at the base of the stalk, separates the cane from its leaves, and then deposits the cane into a cart while blowing the cut leaves back onto the field. Such machines can harvest 30 metric tons of cane each hour, but cane harvested using them must be rapidly transported to the processing plant: once cut, sugarcane begins to lose its sugar content, and damage inflicted on the cane during mechanical harvesting only accelerates this decay.

Processing

Traditionally, sugarcane has been processed in two stages. Sugarcane mills, located in sugarcane producing regions, extract sugar from freshly harvested sugarcane, resulting in raw sugar for later refining, and in mill white sugar for local consumption. Sugar refineries, often located in heavy sugar-consuming regions such as North America, Europe, and Japan, then purify raw sugar to produce refined white sugar, a product that is more than 99% pure sucrose. These two stages are, however, slowly becoming blurred. Increasing affluence in the sugar-producing tropics has led to an increase in demand for refined sugar products in those areas, and there is a trend towards combined milling and refining in these areas.

Milling

In a sugar mill, sugarcane is washed, and then chopped and shredded by revolving knives. The shredded cane is then repeatedly mixed with water and crushed between rollers; the collected juices contain 10–15% sucrose, while the remaining fibrous solids, called bagasse, are burnt for fuel. Bagasse makes a sugar mill more than self-sufficient in energy; the surplus bagasse can be used for animal feed, in paper manufacture, or burnt to generate electricity for the local power grid.

The cane juice is next mixed with lime to adjust its pH to 7. This arrests sucrose's decay into glucose and fructose, and precipitates out some impurities. The mixture then sits, allowing the lime and other suspended solids to settle out, and the clarified juice is then concentrated in a multiple-effect evaporator to make a syrup about 60 wt% in sucrose. This syrup is further concentrated under vacuum until it becomes supersaturated, and then seeded with crystalline sugar. Upon cooling, sugar crystallizes out of the syrup. A centrifuge is used to separate the sugar from the remaining liquid, or molasses. Additional crystallizations may be performed to extract more sugar from the molasses; the molasses remaining after no more sugar can be extracted from it in a cost-effective fashion is called blackstrap.

Raw sugar has a yellow to brown color. If a white product is desired, sulfur dioxide may be bubbled through the cane juice prior to evaporation. This bleaches many color-forming impurities into colorless ones. Sugar bleached white by this sulfitation process is called mill white, plantation white or crystal sugar. This form of sugar is the most commonly consumed form of sugar in sugarcane-producing countries.

Refining

In sugar refining, raw sugar is further purified. First, the raw sugar is mixed with heavy syrup and then centrifuged clean. This process is called affination; its purpose is to wash away the outer coating of the raw sugar crystals, which is less pure than the crystal interior. The remaining sugar is then dissolved to make a syrup, about 70% by weight solids.

The sugar solution is then clarified by the addition of phosphoric acid and calcium hydroxide, which combine to precipitate calcium phosphate. The calcium phosphate particles entrap some impurities and adsorb others, and then float to the top of the tank where they can be skimmed off. An alternative to this phosphatation technique is carbonatation, which is similar, but uses carbon dioxide and calcium hydroxide to produce a calcium carbonate precipitate.

After any remaining solids are filtered out, the clarified syrup is decolorized by filtration through a bed of activated carbon (charred bone was traditionally used in this role, but its use is no longer common). Some remaining color-forming impurities adsorb to the carbon bed.

The purified syrup is then concentrated to supersaturation and repeatedly crystallized under vacuum, to produce white refined sugar. As in a sugar mill, the sugar crystals are separated from the molasses by centrifugation. Additional sugar is recovered by blending the remaining syrup with the washings from affination and again crystallizing to produce brown sugar. When no more sugar can be economically recovered, the final molasses still contains 20–30% sucrose, as well as 15–25% glucose and fructose.

To produce granulated sugar in which the individual sugar grains do not clump together, sugar must be dried. This is accomplished first by drying the sugar in a hot rotary dryer, and then by conditioning the sugar by blowing cool air through it for several days.


Ribbon cane is a subtropical type that was once widely grown in southern United States, as far north as coastal North Carolina. The juice was extracted with horse or mule-powered crushers, then the juice was boiled, similar to maple syrup, in a flat pan, then used in the syrup form as a sweetener for other foods. It is not a commercial crop nowadays, but a few growers try to keep alive the old traditions and find ready sales for their product. Most modern United States sugar cane production is on Hawaii although it is also grown in Florida and Louisiana.

In computer terminology, a Sugarcane is an open-proxy trap set to attract malicious computer users and then capture and monitor the types of malicious traffic that traverse these systems.

See related, see honeypot.

External links

da:Sukkerrr (Saccharum officinarum) de:Zuckerrohr es:Caa de azcar eo:Sukerkano fr:Canne sucre it:Saccharum officinarum he:קנה סוכר nl:Suikerriet ja:サトウキビ pl:Trzcina cukrowa pt:Cana-de-acar

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