Sucrose - Wikipedia
Sugar crystals show melting that often occurs at low temperatures with Several other sugars exhibit similarities in thermal behavior to sucrose melting and . Thermodynamic melting of a substance causes a temperature difference between a .. reaction that produces d-glucose and a fructose derivative. Keywords: Melting point; D-Sucrose; D-Glucose; D-Fructose. 1. Introduction .. fact, there was a difference in the shape of the DSC peaks (Fig. 3). At slow rates. The melting behaviour of sucrose, glucose, fructose and xylose was .. D and L. Enantiomeric or mirror-image relationships between the.
Hydrolysis of sucrose to glucose and fructose by sucrase Figure 5: Intestinal sugar transport proteins Fructose exists in foods either as a monosaccharide free fructose or as a unit of a disaccharide sucrose.
Free fructose is absorbed directly by the intestine. When fructose is consumed in the form of sucrose, it is digested broken down and then absorbed as free fructose. As sucrose comes into contact with the membrane of the small intestine, the enzyme sucrase catalyzes the cleavage of sucrose to yield one glucose unit and one fructose unit, which are then each absorbed. After absorption, it enters the hepatic portal vein and is directed toward the liver.
The mechanism of fructose absorption in the small intestine is not completely understood. Some evidence suggests active transportbecause fructose uptake has been shown to occur against a concentration gradient. Since the concentration of fructose is higher in the lumen, fructose is able to flow down a concentration gradient into the enterocytesassisted by transport proteins.
It appears that the GLUT5 transfer rate may be saturated at low levels, and absorption is increased through joint absorption with glucose. In addition, fructose transfer activity increases with dietary fructose intake.
Fructose malabsorption Several studies have measured the intestinal absorption of fructose using the hydrogen breath test. When fructose is not absorbed in the small intestine, it is transported into the large intestine, where it is fermented by the colonic flora.
Hydrogen is produced during the fermentation process and dissolves into the blood of the portal vein.
Fructose - Wikipedia
This hydrogen is transported to the lungs, where it is exchanged across the lungs and is measurable by the hydrogen breath test. The colonic flora also produces carbon dioxide, short-chain fatty acidsorganic acids, and trace gases in the presence of unabsorbed fructose. Uptake of fructose by the liver is not regulated by insulin.
Production[ edit ] History of sucrose refinement[ edit ] Table sugar production in the 19th century. Sugar cane plantations upper image employed slave or indentured laborers. The picture shows workers harvesting cane, loading it on a boat for transport to the plant, while a European overseer watches in the lower right. The lower image shows a sugar plant with two furnace chimneys.
Sugar plants and plantations were harsh, inhumane work. Sugar nips were required to break off pieces. History of sugar The production of table sugar has a long history. Some scholars claim Indians discovered how to crystallize sugar during the Gupta dynastyaround AD On their return journey, the Greek soldiers carried back some of the "honey-bearing reeds".
Sugarcane remained a limited crop for over a millennium. Sugar was a rare commodity and traders of sugar became wealthy. Venice, at the height of its financial power, was the chief sugar-distributing center of Europe. Only after the Crusades did it begin to rival honey as a sweetener in Europe. The Spanish began cultivating sugarcane in the West Indies in Cuba in The Portuguese first cultivated sugarcane in Brazil in Sugar remained a luxury in much of the world until the 18th century. Only the wealthy could afford it.
In the 18th century, the demand for table sugar boomed in Europe and by the 19th century it had become regarded as a human necessity. Suppliers marketed sugar in novel forms, such as solid cones, which required consumers to use a sugar nipa pliers-like tool, in order to break off pieces.
The demand for cheaper table sugar drove, in part, colonization of tropical islands and nations where labor-intensive sugarcane plantations and table sugar manufacturing could thrive. Growing sugar cane crop in hot humid climates, and producing table sugar in high temperature sugar mills was harsh, inhumane work.
The demand for cheap and docile labor for this work, in part, first drove slave trade from Africa in particular West Africafollowed by indentured labor trade from South Asia in particular India.
The modern ethnic mix of many nations, settled in the last two centuries, has been influenced by table sugar.
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The steam engine first powered a sugar mill in Jamaica inand, soon after, steam replaced direct firing as the source of process heat. During the same century, Europeans began experimenting with sugar production from other crops. Andreas Marggraf identified sucrose in beet root  and his student Franz Achard built a sugar beet processing factory in Silesia Prussia.
However, the beet-sugar industry really took off during the Napoleonic Warswhen France and the continent were cut off from Caribbean sugar.
Inabout 20 percent of the world's sugar was produced from beets.
Melting behaviour of D-sucrose, D-glucose and D-fructose.
Current trends[ edit ] A table sugar factory in England. The tall diffusers are visible to the middle left where the harvest transforms into a sugar syrup.
The boiler and furnace are in the center, where table sugar crystals form. An expressway for transport is visible in the lower left. Table sugar sucrose comes from plant sources. Two important sugar crops predominate: Minor commercial sugar crops include the date palm Phoenix dactyliferasorghum Sorghum vulgareand the sugar maple Acer saccharum. Sucrose is obtained by extraction of these crops with hot water; concentration of the extract gives syrups, from which solid sucrose can be crystallized.
Inworldwide production of table sugar amounted to million tonnes.