Sugars (resource)

Sugars play a vital role in nutrition and account for the basic molecular structure for most living matter. Sugars are refined from sugarcane (a major crop in many tropical countries), sugar beets, and corn. Alcohol (ethanol) from sugar is a major fuel in Brazil, and many other products could come from sugar.

Background

Sugars (saccharides) power chemical reactions and motion for all life. Energy is stored as starch or fat but is burned as sugar. Sugars include some of the simplest carbohydrates, and they are building blocks for more complicated molecules. Common sugars include glucose, fructose, sucrose, cellulose, maltose, and lactose.

History of Use in Food

Demand for sugar and other food flavorings was particularly strong before canning and refrigeration. People often had to eat partially spoiled food, and they eagerly sought ways to improve its flavor. Items with high sugar levels, such as berries and grapes, were especially prized.

Sugarcane has a stem that can be squeezed to deliver a sucrose-rich syrup, and the leftover woody material (bagasse) can be dried and burned to boil off water; molasses syrup or solid sugar can be made in this way. Arab traders brought sugarcane to Europe in the 1100s; in the 1500s, the European colonies in Brazil and the Caribbean provided rich growing fields. So important and valuable were sugar crops that in 1800 the countries of Haiti and the United States had similar gross national products. However, the cravings and rivalries that created sugar empires caused their decline. England and its allies fought a series of wars with France (under Napoleon) in the late 1700s and early 1800s, and British blockades kept molasses out of Europe. Napoleon responded by offering a prize for a process to produce sugar from a European-grown plant. A sugar-beet process won, and cane sugar was never again as centrally important.

Yearly sucrose production from sugarcane and sugar beets is more than 150 million metric tons. Both crops are excellent soil conditioners. Sugarcane is like a tall, periodically harvested grass, so it limits from bare ground. Meanwhile, cane roots steadily grow and increase humus in the soil. Sugar beets require plowing and are dug from the ground during harvesting, but they too leave extensive roots. When sucrose prices rose in the 1950s, high-fructose sweeteners were developed as an alternative. Enzymes are used to break starches into fructose. Corn syrup, a fructose sweetener, is cheaper than sucrose and has displaced much US sucrose use. Elsewhere, fructose syrups are made from wheat, rice, tapioca, and cassava.

Sugar and Alcohol

The fermentation of alcohol has been a major aspect of sugar use since antiquity. Fungi called yeasts break sugars into ethyl alcohol (ethanol); the yeasts can produce only mild alcohol levels. Alcohol, although medically classified as a depressant, can provide a short-term energy boost; it also acts as a mild poison that desensitizes the central nervous system, allowing drinkers to feel relaxed. Ancient Egyptians and Mesopotamians fermented grains into beer, while Greeks and Phoenicians traded wine from grapes in giant pottery jugs. In the Middle Ages, alchemists experimented with distillation, a process in which a substance boiled out of one substance is cooled back into liquid elsewhere. Distillation transformed beers and wines into whiskeys and brandies, alcoholic drinks several times more potent.

Caribbean sugar and alcohol formed one leg of the “triangle trade” from the 1600s through the early 1800s. New Englanders sold fish for Caribbean molasses, fermented it, and distilled it into rum. They traded rum in Africa for enslaved people, sold largely in the Caribbean.

Fuel and Other Uses

Ethyl alcohol (ethanol) can burn more efficiently than gasoline in the internal combustion engines used in automobiles. However, because gasoline has been cheaper historically, research and development work on ethanol as a fuel was minimal until the 1970s. The 1973 energy crisis involved oil shortages and soaring prices, and it stimulated many experimental ethanol programs. Most experiments were abandoned when oil prices dropped in the mid-1980s, but Brazil persevered in a national program of sugarcane alcohol fuel.

Even Brazilian ethanol is only barely economically competitive with fossil fuels. The major problem is that energy losses in the manufacture of ethanol include fuel for tending the fields and gathering cane, energy lost to yeasts (about one-half, although the yeasts do yield a high-protein by-product), and another one-half of the remainder expended for distilling the material to 95 percent alcohol. Suggested improvements include developing more efficient yeasts and performing the distillation process under a partial vacuum (which would allow continuous processing rather than batch processing).

In 2008, the United States and Brazil were the largest producers and consumers of ethanol. In many states in the United States, an ethanol blended gasoline is mandated, with up to 10 percent ethanol added to gasoline. In Brazil, the mandate is for a 25 percent blend. Fluctuations in the cost of gasoline and the cost of ethanol continue to unsettle the development of ethanol as a renewable fuel.

Theoretically, the most efficient way to use sugar energy would be the development of electrical fuel cells that would take energy from sugar just as living organisms do. Losses from yeast digestion and distillation would be eliminated, and a fuel cell might achieve 50 percent efficiency rather than the 25 percent of internal combustion engines, yielding eight times more energy. This approach could create an energy revolution if the technical problems could be overcome. (Energy-efficient processes must be developed for saccharification, or hydrolysis, of cellulose from wood and garbage.)

Sugars can also be nutrients for generating other products. Specialized groups of other cells, such as juice-producing cells from oranges or fiber-producing cells from cotton, can be cultured with sugar nutrients, for example, and genetic engineering has developed yeasts that produce specialty chemicals such as catalysts.

Bibliography

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