Science Fair Project Encyclopedia
- This article deals with sugar as food and as an important, widely traded commodity; the word also has other uses; see Sugar (disambiguation)
A sugar is a form of carbohydrate; the most commonly used sugar is a white crystalline solid, sucrose; used to alter the flavor and properties ('mouthfeel', preservation, texture) of beverages and food. The "simple" sugars, such as glucose (which is produced from sucrose by enzymes or acid hydrolysis), are a store of energy which is used by biological cells.
Table sugar or sucrose is extracted from plant sources. The most important two sugar crops are sugarcane (Saccharum sp.) and sugar beets (Beta vulgaris), in which sugar can account for 12%–20% of the plant's dry weight. Some minor commercial sugar crops include the date palm (Phoenix dactylifera), sorghum (Sorghum vulgare), and the sugar maple (Acer saccharum). In the financial year 2001/2002, 134.1 million tonnes of sugar were produced worldwide.
The major cane sugar producing countries are countries with warm climates, such as Australia, Brazil, and Thailand. In 2001/2002 there was over twice as much sugar produced in developing countries as in developed countries. The greatest quantity of sugar is produced in Latin America and the Caribbean nations, and in the Far East.
The sugar beet regions are in cooler climates; North West and Eastern Europe, Northern Japan, plus some areas in the United States including California. The beet growing season ends with the start of harvesting around September. Harvesting and processing continues until March in some cases. The duration of harvesting and processing is influenced by the availability of processing plant capacity, and weather - harvested beet can be laid up until processed but frost damaged beet becomes effectively unprocessable.
The world's second largest sugar exporter is the EU. The Common Agricultural Policy of the EU sets maximum quotas for members production to match supply and demand, and a price. Excess production quota is exported (approx 5 million tonnes in 2003). Part of this is "quota" sugar which is subsidised from industry levies, the remainder (approx half) is "C quota" sugar which is sold at market price without subsidy. These subsidies and a high import tariff make it difficult for other countries to export to the EU states, or compete with it on world markets. The U.S. sets high sugar prices to support its producers with the effect that many sugar consumers have switched to corn syrup (beverage manufacturers) or moved out of the country (candy makers).
The sugar market is also under attack from the cheap prices of glucose syrups produced from wheat and corn (maize). In combination with artificial sweeteners drinks manufacturers can produce very low cost products.
The raw vegetable material is crushed, and the juice is collected and filtered. The liquid is then treated (often with lime) to remove impurities, this is then neutralised with sulfur dioxide. The juice is then boiled, sediment settles to the bottom and can be dredged out, scum rises to the surface and this is skimmed off. The heat is removed and the liquid crystallises, usually while being stirred, to produce sugar which can be poured into moulds. A centrifuge can also be used during crystallisation.
The washed beet is sliced, and the sugar extracted with hot water in a 'diffuser'. Impurities are precipitated with an alkaline solution "milk of lime" and carbon dioxide from the lime kiln. After filtration the juice is concentrated by evaporation to a content of about 70% solids. The sugar is extracted by controlled crystallisation. The sugar crystals are removed by a centrifuge and the liquid recycled in the crystalliser stages. Liquid from which no more sugar can be economically removed is lost from the process as molasses and used in cattle food.
The white sugar produced is sieved into different grades for selling.
Cane vs Beet
There is little perceptible difference between sugar produced from beet and that from cane. Testing for impurities can distinguish the two, and these have been developed to reduce fraudulent abuse of EU subsidies, and also aid detection of adulteration of fruit juice.
The residues of sugar production differ substantially. While Cane molasses can be used as an ingredient, beet molasses is unpalatable and generally used for industrial fermentation or as animal feedstuff. Cane pulp can be burnt, beet pulp is dried, pelleted and used as an animal feedstuff.
Types of culinary sugar
Raw sugars are yellow to brown sugars made from clarified cane juice, boiled down to a crystalline solid with minimal chemical processing. Types of raw sugar available as a specialty item outside the tropics include demerara, muscovado, and turbinado. Mauritius and Malawi are significant exporters of such specialty sugars. Raw sugar is sometimes prepared as loaves rather than as a crystalline powder: in this technique, sugar and molasses are poured together into molds and allowed to dry. The resulting sugar cakes or loaves are called jaggery or gur in India, pingbian tong in China, and panela, panocha, pile, and piloncillo in various parts of Latin America.
Mill white sugar, also called plantation white, crystal sugar, or superior sugar, is raw sugar whose colored impurities have not been removed, but rather bleached white by exposure to sulfur dioxide. This is the most common form of sugar in sugarcane growing areas, but does not store or ship well; after a few weeks, its impurities tend to promote discoloration and clumping.
Blanco directo is a white sugar common in India and other south Asian countries. In producing blanco directo, many impurities are precipitated out of the cane juice by using phosphatation a treatment with phosphoric acid and calcium hydroxide similar to the carbonatation technique used in beet sugar refining. In terms of sucrose purity, blanco directo is more pure than mill white, but less pure than white refined sugar.
White refined sugar is the most common form of sugar in North America and Europe. Refined sugar can be made by dissolving raw sugar and purifying it with a phosphoric acid method similar to that used for blanco directo, a carbonatation process involving calcium hydroxide and carbon dioxide, or by various filtration strategies. It is then further decolorized by filtration through a bed of activated carbon or bone char. Beet sugar refineries produce refined white sugar directly without an intermediate raw stage. White refined sugar is typically sold as granulated sugar, which has been dried to prevent clumping.
Granulated sugar is available in various crystal sizes, for home and industrial use depending on the application:
- Coarse-grained sugars, such as sanding sugar are favored for decorating cookies and other desserts.
- Normal granulated for table use is typically around 0.5 mm across
- Finer grades are produced by selectively sieving the granualted sugar.
- caster (0.35 mm)
- superfine sugar, and are favored for sweetening drinks or preparing meringue.
- Finest grades
- Powdered sugar, confectioner's sugar (0.060 mm), or icing sugar (0.024 mm), are produced by grinding sugar to a fine powder. A small amount of anti-caking agent to prevent clumping may be added, this is either cornstarch(1%-3%) or tri-calcium phosphate.
Brown sugars are obtained in the late stages of sugar refining, or by coating white refined sugar with a cane molasses syrup. Their color and taste become stronger with increasing molasses content, as does their moisture retaining properties.
In biochemistry, a sugar is the simplest molecule that can be identified as a carbohydrate. These include monosaccharides and disaccharides, trisaccharides and the oligosaccharides; these being sugars composed of 1, 2, 3 or more units. Sugars contain either aldehyde groups (-CHO) or ketone groups (C=O), where there are carbon-oxygen double bonds, making the sugars reactive. Most sugars conform to (CH2O)n where n is between 3 and 7. A notable exception is deoxyribose, which as the name suggests is "missing" an oxygen. As well as being classified by their reactive group, sugars are also classified by the number of carbons they contain. Derivatives of trioses (C3H6O3) are intermediates in glycolysis. Pentoses ( 5 carbon sugars) include ribose and deoxyribose, which are present in nucleic acids. Ribose is also a component of several chemicals that are important to the metabolic process, including NADH and ATP. Hexoses ( 6 carbon sugars) include glucose which is a universal substrate for the production of energy in the form of ATP. Through photosynthesis plants produce glucose which is then converted for storages as an energy reserve in the form of other carbohydrates such as starch, or as in cane and beet as sucrose.
Many pentoses and hexoses are capable of forming ring structures. In these closed-chain forms the aldehyde or ketone group is not free, so many of the reactions typical of these groups cannot occur. Glucose in solution exists mostly in the ring form at equilibrium, with less than 0.1% of the molecules in the open-chain form.
Monosaccharides in a closed-chain form can form glycosidic bonds with other monosaccharides, creating disaccharides, such as sucrose, and polysaccharides such as starch. Glycosidic bonds must be hydrolysed or otherwise broken by enzymes before such compounds can be used in metabolism. After digestion and absorption the pricipal monosaccharieds present in the blood and internal tissues are: glucose, fructose, and galactose.
The term "glyco-" indicates the presence of a sugar in an otherwise non-carbohydrate substance: for example, a glycoprotein is a protein to which one or more sugars are connected.
Sucrose can be converted by hydrolysis into a syrup of fructose and glucose, producing what is called invert sugar. This resulting syrup is sweeter than the original sucrose, and is useful for making confections sweeter and softer in texture.
Sugarcane is a tropical grass, probably native to New Guinea. In the course of prehistory, its culture spread throughout the Pacific Islands and into India. By 800 B.C., it was being grown in China as well. Westerners discovered sugarcane in the course of military expeditions into India. Nearchos, one of Alexander the Great's commanders, described it as "a reed that gives honey without bees."
Originally, the cane was chewed raw to extract its sweetness. Sugar refining was developed in the Middle East, India and China, where it became a staple of cooking and desserts. In early refining methods, the cane was ground or pounded to extract the juice, and the juice then boiled down or dried in the sun to yield sugary solids that resembled gravel. The Sanskrit word for sugar (shakkara), also means gravel. Similarly, an ancient Chinese word for sugar means "stone honey."
Later sugar spread to other areas of the world through trade. It arrived in Europe with the arrival of the Moors. Crusaders also brought sugar home with them after their campaigns in the Holy Land, as there they encountered caravans carrying this "sweet salt" as it was called. While sugar cane could not be grown in northern Europe, sugar could be extracted from certain beets and these began to be widely cultivated around 1801, after the British control of the seas during the Napoleonic wars isolated mainland Europe from the Caribbean.
The History of Sugar in the West
In the 1390s, a better press, which doubled the juice obtained from the cane, was developed. This permitted economic expansion of sugar plantations to Andalusia and the Algarve. In the 1420s, sugar was carried to the Canary Islands and Madeira and Porto Santa Maria.
In 1493, Christopher Columbus stopped, intending to stay only four days, at Gomera in the Canary Islands, for wine and water. Columbus became romantically involved with the Governor of the Island, Beatrice. He stayed a month. When he finally sailed she gave him cuttings of sugarcane, the first to reach the New World.
The Portuguese took sugar to Brazil. Hans Staden, published in 1555, writes that by 1540 there were 800 sugar mills on Santa Catalina Island and another 2000 up the north coast of Brazil, Demarara and Surinam. Approximately 3000 small mills built before 1550 in the New World created an unprecedented demand for cast iron gears, levers, axles and other implements. Specialist in mold making and iron casting were inevitably created in Europe by the expansion of sugar. Sugar mill construction is the missing link of the technological skills needed for the Industrial Revolution that is recognized as beginning in the first part of the 1600s.
After 1625, the Dutch carried sugarcane from South America to the Caribbean islands from Barbados to the Virgin Islands. In the years 1625 to 1750, sugar was worth its weight in gold. Price declined slowly as production became multi-sourced especially through British colonial policy. Sugar production also increased in the American Colonies, Cuba, and Brazil. African slaves became the dominant plantation worker as they were resistant to the diseases of malaria and yellow fever. European indentured servants were in shorter supply, succeptible to disease and a less economic investment. Local Native Americans had been reduced by European diseases like smallpox.
With the European colonization of the Americas, the Caribbean became the world's largest source of sugar. Sugar cane could be grown on these islands using slave labour at vastly lower prices than sugar beets could be grown in Europe, or cane sugar imported from the East. Thus the economies of entire islands such as Guadaloupe and Barbados were based on sugar production. The largest sugar producer in the world, by 1750, was the French colony known as Saint-Domingue, which is today the independent country of Haiti. Jamaica was another major producer in the 1700s.
During the eighteenth century, sugar became enormously popular and went through a series of booms. The main reason for the heightened demand and production of sugar was a great change in the eating habits of many Europeans. For example, they began consuming jams, candy, tea, coffee, cocoa, processed foods, and other sweet victuals in much greater numbers. Reacting to this increasing craze, the islands took advantage of the situation and began harvesting sugar in extreme amounts. In fact, they produced up to ninety percent of the sugar that the western Europeans consumed. Of course some islands were more successful than others when it came to producing the product. For instance, Barbados and the British Leewards can be said to have been the most successful in the production of sugar because it counted for ninety-three and ninety-seven percent of the island’s exports, respectively.
Planters later began developing ways to boost production even more. For example, they began using more animal manure when growing their crops. They also developed more advanced mills and began using better types of sugar cane. Despite these and other improvements, the prices of sugar reached soaring heights, especially during events such as the revolt against the Dutch and the Napoleonic wars. Sugar was a highly desired product, and the islands knew exactly how to take advantage of the situation.
As Europeans established sugar plantations on these larger Caribbean islands, prices fell, especially in Britain. What had previously been a luxury good began, by the eighteenth century, to be commonly consumed by all levels of society. At first most sugar in Britain was used in tea, but later candies and chocolates became extremely popular. Sugar was commonly sold in solid cones and required a sugar nip, a pliers-like tool, to break off pieces.
Sugar cane quickly exhausts the soil and larger islands with fresher soil were pressed into production in the nineteenth century. For example, it was in this century that Cuba rose as the richest land in the Caribbean (with sugar being its dominant crop) because it was the only major island that was free of mountainous terrain. Instead, nearly three-quarters of its land formed a rolling plain which was ideal for planting crops. Cuba also prospered above other islands because they used better methods when harvesting the sugar crops. They had been introduced to modern milling methods such as water mills, enclosed furnaces, steam engines, and vacuum pans. All these things increased their production and production rate.
After the world's only successful slave revolution established the independent nation of Haiti, sugar production in that country declined and Cuba replaced Saint-Domingue as the world's largest producer. Production spread to South America as well as to new European colonies in Africa and the Pacific.
The rise of Beet
In 1747 the German chemist Andreas Marggraf identified sucrose in beet root. This discovery remained a mere curiosity for some time, but eventually his student Franz Achard built a sugarbeet processing factory at Cunern in Silesia, under the patronage of Frederick William III of Prussia. While never profitable, this plant operated from 1801 until being destroyed during the Napoleonic Wars.
Napoleon, cut off from Caribbean imports by a British blockade and at any rate not wanting to fund British merchants, banned sugar imports in 1813. The beet sugar industry that emerged in its place grew, and today, cane and beet sugar enjoy approximately equal world production.
While it is no longer grown by slaves, sugar growing in developing countries continues to this day to be associated with workers earning minimal wages and living in extreme poverty. Cuba was a large producer of sugar in the 20th century until the collapse of the Soviet Union took away their export market and the industry collapsed.
In the developed countries, the sugar industry is machine reliant, with a low requirement for manpower. A large beet refinery producing around 1,500 tonnes of sugar a day needs a permanent workforce of about 150 for 24 hour production.
Beginning in the late 18th century, sugar production became increasingly mechanized. The steam engine was first used to power a sugar mill in Jamaica in 1768, and soon thereafter, steam replaced direct firing as the source of process heat.
Soon, steam also replaced direct firing as the source of process heat. In 1813, the British chemist Edward Charles Howard invented a sugar refining method in which the cane juice was boiled not in an open kettle, but in a closed vessel heated by steam and held under partial vacuum. At reduced pressure, water boils at a lower temperature, and this development both saved fuel and reduced the amount of sugar lost through carmelization. Further gains in fuel efficiency were achieved through the multiple-effect evaporator, designed by the African-American engineer Norbert Rillieux perhaps as early as the 1820s, although the first working model was not built until 1845. This system consisted of a series of vacuum pans, each held at a lower pressure than the previous. The vapors from each pan were used to heat the next, and little heat wasted. Today, multiple-effect evaporators are employed widely in many industries for evaporating water.
In 2003, a report was commissioned by two U.N. agencies, the World Health Organization (WHO) and the Food and Agriculture Organization (FAO), compiled by a panel of 30 international experts. It stated that sugar should not account for more than 10% of a healthy diet. However, the Sugar Association of the US insists that other evidence indicates that a quarter of our food and drink intake can safely consist of sugar.
There is an on-going argument as to the value of extrinsic sugar (sugar added to food) compared to that of intrinsic (sugar, seldom sucrose, naturally present in food).
In many industrialized countries, sugar is among the most heavily subsidized agricultural products. The European Union, the United States, and Japan all maintain elevated price floors for sugar though subsidizing domestic production and imposing high tariffs on imports. In recent years, sugar prices in these countries have been three times the price on the international market.
In international trade bodies, especially the World Trade Organization, many developing countries in tropical climates have argued that because their cane sugar exports are essentially excluded from these sugar markets, they receive lower prices than they would under free trade. While both the European Union and United States maintain trade agreements whereby certain developing and least-developed countries can sell certain quantities of sugar into their markets, free of the usual import tariffs, countries outside these preferred trade regimes have complained that these arrangments violate the "most favored nation" principle of international trade, and that the European practice of subsidizing sugar exports by paying exporters the difference between the European and international price only further exacerbates the world sugar surplus.
In 2004, the WTO sided with a group of cane sugar exporting nations, led by Brazil, and ruled that the EU sugar regime and the accompanying ACP-EU Sugar Protocal, whereby a group of African, Caribbean, and Pacific coutnries were given preferential access to the European sugar market, were illegal. What, if any, reforms this ruling will have on European sugar policy remains to be seen.
Small quantities of sugar, especially specialty grades of sugar, are sold as 'fair trade' commodities; these products are produced and sold with the understanding that a larger-than-usual fraction of the revenue supports small farmers in the devloping world.
- Expert Report on diet and chronic disease (WHO/FAO)
- Sugar industry threatens to scupper WHO (Guardian)
- European Commission proposes to overhaul EU sugar regime (sugartraders.co.uk)
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