saccharose

Sucrose is a type of

sugar

made up of one

molecule

of

glucose

and one molecule of

fructose

joined together. It is a disaccharide, a molecule composed of two monosaccharides: glucose and fructose. Sucrose is produced naturally in plants, from which table sugar is refined. It has the molecular formula .

For human consumption, sucrose is extracted and refined from either

sugarcane

or sugar beet.

Sugar mill

s – typically located in

tropical regions

near where sugarcane is grown – crush the cane and produce raw sugar which is shipped to other factories for refining into pure sucrose. Sugar beet factories are located in temperate climates where the beet is grown, and process the beets directly into refined sugar. The sugar refining process involves washing the raw sugar crystals before dissolving them into a sugar syrup which is filtered and then passed over carbon to remove any residual colour. The sugar syrup is then concentrated by boiling under a vacuum and crystallized as the final purification process to produce crystals of pure sucrose that are clear, odorless, and sweet.

Sugar is often an added ingredient in food production and food

recipe

s. About 185 million tonnes of sugar were produced worldwide in 2017.

Sucrose is particularly dangerous from the point of view of tooth decay because ''Streptococcus mutans'' bacteria convert it into a sticky, extracellular,

dextran

-based polysaccharide that allows them to cohere, forming plaque. Sucrose is the only sugar that bacteria can use to form this sticky polysaccharide.

Etymology

The word ''sucrose'' was coined in 1857, by the English chemist William Miller from the

French

("sugar") and the generic chemical suffix for sugars ''-ose''. The abbreviated term ''Suc'' is often used for ''sucrose'' in scientific literature.

The name ''saccharose'' was coined in 1860 by the French chemist

Marcellin Berthelot

. Saccharose is an obsolete name for sugars in general, especially sucrose.

Physical and chemical properties

Structural O-α-D-glucopyranosyl-(1→2)-β-D-fructofuranoside

In sucrose, the

monomer

s glucose and fructose are linked via an ether bond between C1 on the glucosyl subunit and C2 on the fructosyl unit. The bond is called a glycosidic linkage. Glucose exists predominantly as a mixture of α and β "pyranose" anomers, but sucrose has only the α form. Fructose exists as a mixture of five

tautomer

s but sucrose has only the β-D-fructofuranose form. Unlike most disaccharides, the glycosidic bond in sucrose is formed between the reducing ends of both glucose and fructose, and not between the reducing end of one and the non-reducing end of the other. This linkage inhibits further bonding to other saccharide units, and prevents sucrose from spontaneously reacting with cellular and circulatory macromolecules in the manner that glucose and other reducing sugars do. Since sucrose contains no anomeric hydroxyl groups, it is classified as a non-

reducing sugar

.

Sucrose crystallizes in the

monoclinic

space group P2₁ with room-temperature lattice parameters ''a'' = 1.08631 nm, ''b'' = 0.87044 nm, ''c'' = 0.77624 nm, β = 102.938°.

The purity of sucrose is measured by

polarimetry

, through the rotation of plane-polarized light by a sugar solution. The specific rotation at using yellow "sodium-D" light (589 nm) is +66.47°. Commercial samples of sugar are assayed using this parameter. Sucrose does not deteriorate at ambient conditions.

Thermal and oxidative degradation

Sucrose does not melt at high temperatures. Instead, it decomposes at to form caramel. Like other carbohydrates, it combusts to

carbon dioxide

and water. Mixing sucrose with the oxidizer

potassium nitrate

produces the fuel known as

rocket candy

that is used to propel amateur rocket motors.

This reaction is somewhat simplified though. Some of the carbon does get fully oxidized to carbon dioxide, and other reactions, such as the water-gas shift reaction also take place. A more accurate theoretical equation is:

Sucrose burns with

chloric acid

, formed by the reaction of

hydrochloric acid

and potassium chlorate:

Sucrose can be dehydrated with

sulfuric acid

to form a black,

carbon

-rich solid, as indicated in the following idealized equation:

The formula for sucrose's decomposition can be represented as a two-step reaction: the first simplified reaction is dehydration of sucrose to pure carbon and water, and then carbon oxidises to with from air.

Hydrolysis

Hydrolysis

breaks the glycosidic bond converting sucrose into

glucose

and

fructose

.

Hydrolysis

is, however, so slow that solutions of sucrose can sit for years with negligible change. If the

enzyme

sucrase

is added, however, the reaction will proceed rapidly. Hydrolysis can also be accelerated with acids, such as cream of tartar or lemon juice, both weak acids. Likewise, gastric acidity converts sucrose to glucose and fructose during digestion, the bond between them being an acetal bond which can be broken by an acid.

Given (higher) heats of combustion of 1349.6 kcal/mol for sucrose, 673.0 for glucose, and 675.6 for fructose, hydrolysis releases about per mole of sucrose, or about 3 small calories per gram of product.

Synthesis and biosynthesis of sucrose

The

biosynthesis

of sucrose proceeds via the precursors

UDP-glucose

and

fructose 6-phosphate

, catalyzed by the enzyme sucrose-6-phosphate synthase. The energy for the reaction is gained by the cleavage of

uridine diphosphate

(UDP).
Sucrose is formed by plants,

algae

and cyanobacteria but not by other

organism

s. Sucrose is the end product of

photosynthesis

and is found naturally in many food plants along with the monosaccharide

fructose

. In many fruits, such as

pineapple

and

apricot

, sucrose is the main sugar. In others, such as

grapes

and

pear

s, fructose is the main sugar.

Chemical synthesis

After numerous unsuccessful attempts by others, Raymond Lemieux and George Huber succeeded in synthesizing sucrose from acetylated glucose and fructose in 1953.

Sources

In nature, sucrose is present in many plants, and in particular their roots, fruits and

nectar

s, because it serves as a way to store energy, primarily from

photosynthesis

. Many mammals, birds, insects and bacteria accumulate and feed on the sucrose in plants and for some it is their main food source. Although

honeybee

s consume sucrose, the

honey

they produce consists primarily of

fructose

and

glucose

, with only trace amounts of sucrose.

As fruits ripen, their sucrose content usually rises sharply, but some fruits contain almost no sucrose at all. This includes grapes, cherries, blueberries, blackberries, figs, pomegranates, tomatoes, avocados, lemons and limes.

Sucrose is a naturally occurring sugar, but with the advent of industrialization, it has been increasingly refined and consumed in all kinds of processed foods.

Production

History of sucrose refinement

The production of table sugar has a long history. Some scholars claim Indians discovered how to crystallize sugar during the Gupta dynasty, around AD 350.
Adas, Michael (2001)
''Agricultural and Pastoral Societies in Ancient and Classical History''
. Temple University Press. . p. 311.

Other scholars point to the ancient manuscripts of China, dated to the 8th century BC, where one of the earliest historical mentions of

sugar cane

is included along with the fact that their knowledge of sugar cane was derived from India. By about 500 BC, residents of modern-day India began making sugar syrup, cooling it in large flat bowls to produce raw sugar crystals that were easier to store and transport. In the local Indian language, these crystals were called (), which is the source of the word ''candy''.

The army of

Alexander the Great

was halted on the banks of river

Indus

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