Sucrose

Sucrose
Names
IUPAC name
(2R,3R,4S,5S,6R)-2-[(2S,3S,4S,5R)-3,4-dihydroxy-2,5-bis(hydroxymethyl)oxolan-2-yl]oxy-6-(hydroxymethyl)oxane-3,4,5-triol
Other names
Sugar; Saccharose; α-D-glucopyranosyl-(1→2)-β-D-fructofuranoside

β-D-fructofuranosyl-(2→1)-α-D-glucopyranoside; β-(2S,3S,4S,5R)-fructofuranosyl-α-(1R,2R,3S,4S,5R)-glucopyranoside; α-(1R,2R,3S,4S,5R)-glucopyranosyl-β-(2S,3S,4S,5R)-fructofuranoside
, dodecacarbon monodecahydrate

((2R,3R,4S,5S,6R)-2-[(2S,3S,4S,5R)-3,4-dihydroxy-2,5-bis(hydroxymethyl)oxapent-2-yl]oxy-6-(hydroxymethyl)oxahexane-3,4,5-triol)
Identifiers
57-50-1 YesY
ChEBI CHEBI:17992 YesY
ChEMBL ChEMBL253582 YesY
ChemSpider 5768 YesY
DrugBank DB02772 YesY
EC Number 200-334-9
5411
Jmol interactive 3D Image
PubChem 5988
RTECS number WN6500000
UNII C151H8M554 YesY
Properties[1]
C12H22O11
Molar mass 342.30 g/mol
Appearance white solid
Density 1.587 g/cm3, solid
Melting point None; decomposes at 186 °C (367 °F; 459 K)
2000 g/L (25 °C)
log P −3.76
+66.47°
Structure
Monoclinic
P21
Hazards
Safety data sheet ICSC 1507
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 0: Exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. E.g., sodium chloride Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
1
0
0
Lethal dose or concentration (LD, LC):
29700 mg/kg (oral, rat)[2]
US health exposure limits (NIOSH):
TWA 15 mg/m3 (total) TWA 5 mg/m3 (resp)[3]
TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp)[3]
N.D.[3]
Related compounds
Related compounds
 Lactose
Maltose
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
YesY verify (what is YesYN ?)
Infobox references

Sucrose is a common, naturally occurring carbohydrate found in many plants and plant parts. Saccharose is an obsolete name for sugars in general, especially sucrose.[4] The molecule is a disaccharide combination of the monosaccharides glucose and fructose with the formula C12H22O11.

Sucrose is often extracted and refined from either cane or beet sugar for human consumption. Modern industrial sugar refinement processes often involves bleaching and crystallization also, producing a white, odorless, crystalline powder with a sweet taste of pure sucrose, devoid of vitamins and minerals. This refined form of sucrose is commonly referred to as table sugar or just sugar. It plays a central role as an additive in food production and food consumption all over the world. About 175 million metric tons of sucrose sugar were produced worldwide in 2013.[5]

The word "sucrose" was coined in 1857 by the English chemist William Miller[6] from the French sucre ("sugar") and the generic chemical suffix for sugars -ose. The abbreviated term Suc is often used for sucrose in scientific literature.

Physical and chemical properties

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

In sucrose, the components 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 two isomeric "pyranoses" (α and β), but only one of these forms links to the fructose. Fructose itself exists as a mixture of "furanoses", each of which having α and β isomers, but only one particular isomer links to the glucosyl unit. What is notable about sucrose is that, unlike most disaccharides, the glycosidic bond is formed between the reducing ends of both glucose and fructose, and not between the reducing end of one and the nonreducing end of the other. This linkage inhibits further bonding to other saccharide units. Since it 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°.[7][8]

The purity of sucrose is measured by polarimetry, through the rotation of plane-polarized light by a solution of sugar. The specific rotation at 20 °C 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

Solubility of sucrose in water vs. temperature
T (°C) S (g/mL)
50 2.59
55 2.73
60 2.89
65 3.06
70 3.25
75 3.46
80 3.69
85 3.94
90 4.20

The formula for sucrose decomposition can be represented as a 2 step reaction: the first is dehydration to pure carbon and water, then carbon oxidizes to CO2 with O2 from air.

C12H22O11 + heat → 12C + 11H2O
12C + 12O2 → 12CO2

Sucrose does not melt at high temperatures. Instead, it decomposes—at 186 °C (367 °F)—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.[9]

C12H22O11 + 6 KNO3 → 9 CO + 3 N2 + 11 H2O + 3 K2CO3

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:

C12H22O11 + 6.288 KNO3 → 3.796 CO2 + 5.205 CO + 7.794 H2O + 3.065 H2 + 3.143 N2 + 2.998 K2CO3 + 0.274 KOH [10]

Sucrose burns with chloric acid, formed by the reaction of hydrochloric acid and potassium chlorate:

8 HClO3 + C12H22O11 → 11 H2O + 12 CO2 + 8 HCl

Sucrose can be dehydrated with sulfuric acid to form a black, carbon-rich solid, as indicated in the following idealized equation:

H2SO4 (catalyst) + C12H22O11 → 12 C + 11 H2O + heat (and some H2O + SO3 as a result of the heat).

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.[11] 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.

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 and cyanobacteria but not by other organisms. Sucrose 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 pears, fructose is the main sugar.

Chemical synthesis

Model of sucrose molecule

Although sucrose is almost invariably isolated from natural sources, its chemical synthesis was first achieved in 1953 by Raymond Lemieux.[12]

Sources

In nature, sucrose is present in many plants, and in particular their roots, fruits and nectars, because it serves as a way to store energy, primarily from photosynthesis.[13][14] Many mammals, birds, insects and bacteria accumulate and feed on the sucrose in plants and for some it is their main food source. Seen from a human consumption perspective, honeybees are especially important because they accumulate sucrose and produce honey, an important foodstuff all over the world. The carbohydrates in honey itself primarily consists of fructose and glucose with trace amounts of sucrose only.[15]

As fruits ripen, their sucrose content usually rise 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

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.[16]
A sugarloaf was a traditional form for sugar from the 17th to 19th centuries. Sugar nips were required to break off pieces.
Main article: History of sugar

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.[17]

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.[18] Further, it appears that by about 500 BC, residents of present-day India began making sugar syrup and cooling it in large flat bowls to make raw table sugar crystals that were easier to store and transport. In the local Indian language, these crystals were called khanda (खण्ड), which is the source of the word candy.[19]

The army of Alexander the Great was halted on the banks of river Indus by the refusal of his troops to go further east. They saw people in the Indian subcontinent growing sugarcane and making granulated, salt-like sweet powder, locally called sākhar (साखर), pronounced as sakcharon (ζακχαρον) in Greek (Modern Greek, zachari ζάχαρη). 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.[18] Arabs started producing it in Sicily and Spain. 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 1506 (Cuba in 1523). The Portuguese first cultivated sugarcane in Brazil in 1532.

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.[20] The use of sugar grew from use in tea, to cakes, confectionery and chocolates. Suppliers marketed sugar in novel forms, such as solid cones, which required consumers to use a sugar nip, a 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 Africa), followed by indentured labor trade from South Asia (in particular India).[16][21][22] Millions of slaves, followed by millions of indentured laborers were brought into the Caribbean, Indian Ocean, Pacific Islands, East Africa, Natal, north and eastern parts of South America, and southeast Asia. The modern ethnic mix of many nations, settled in the last two centuries, has been influenced by table sugar.[23][24][25]

Beginning in the late 18th century, the production of sugar became increasingly mechanized. The steam engine first powered a sugar mill in Jamaica in 1768, and, 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[26] 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 Wars, when France and the continent were cut off from Caribbean sugar. In 2010, about 20 percent of the world's sugar was produced from beets.[27]

Today, a large beet refinery producing around 1,500 tonnes of sugar a day needs a permanent workforce of about 150 for 24-hour production.

Current trends

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: sugarcane (Saccharum spp.) and sugar beets (Beta vulgaris), in which sugar can account for 12% to 20% of the plant's dry weight. Minor commercial sugar crops include the date palm (Phoenix dactylifera), sorghum (Sorghum vulgare), and 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. In 2013, worldwide production of table sugar amounted to 175 million tonnes.[5]

Most cane sugar comes from countries with warm climates, because sugarcane does not tolerate frost. Sugar beets, on the other hand, grow only in cooler temperate regions and do not tolerate extreme heat. About 80 percent of sucrose is derived from sugarcane, the rest almost all from sugar beets.

In 2010, Brazil, India, European Union, China, Thailand, and United States were the major sugar-producing countries in the world.[28] Brazil produced about 40 million tonnes of table sugar in 2013, while India produced 25 million, EU-27 countries 16 million, China 14 million, Thailand about 10 million, and United States over 7 million.[5] The country rankings for table sugar production change with each year's sugarcane crop harvest and as new sugar production plants are commissioned worldwide.

Viewed by region, Asia predominates in cane sugar production, with large contributions from India, China, Thailand, and other countries combining to account for 40% of global production in 2006. South America comes in second place with 32% of global production; Africa and Central America each produce 8% and Australia 5%. The United States, the Caribbean, and Europe make up the remainder, with roughly 3% each.[28]

Beet sugar comes from regions with cooler climates: northwest and eastern Europe, northern Japan, plus some areas in the United States (including California). In the northern hemisphere, the beet-growing season ends with the start of harvesting around September. Harvesting and processing continues until March in some cases. The availability of processing plant capacity and the weather both influence the duration of harvesting and processing – the industry can store harvested beets until processed, but a frost-damaged beet becomes effectively unprocessable.

Brazil is the world's largest sugar exporter at 29 million tonnes in the year 2013.[5] The European Union (EU) has become the world's second-largest sugar exporter. The Common Agricultural Policy of the EU sets maximum quotas for members' production to match supply and demand, and a price. Europe exports excess production quota (approximately 5 million tonnes in 2003). Part of this, "quota" sugar, gets subsidised from industry levies, the remainder (approximately half) sells as "C quota" sugar at market prices without subsidy. These subsidies and a high import tariff make it difficult for other countries to export to the EU states, or to compete with the Europeans on world markets.

The United States sets high sugar prices to support its producers, with the effect that many former purchasers of sugar have switched to corn syrup (beverage manufacturers) or moved out of the country (candy manufacturers).

India consumes the most sugar at 26 million tonnes of table sugar in 2013. EU-27 is in second place at 18 million and China is third at above 16 million.[5]

Low prices of sugar are expected to stimulate global consumption and trade, with exports forecast 4 percent higher at 59 million tons.[5]

The low prices of glucose syrups produced from wheat and corn (maize) threaten the traditional sugar market. Used in combination with artificial sweeteners, they can allow drink manufacturers to produce very low-cost goods.

High-fructose corn syrup

In the USA there are tariffs on the importation of sugar, and subsidies for the production of maize (corn). High-fructose corn syrup (HFCS) is derived from corn, and significantly cheaper there than sucrose as a sweetener.[29] This has led to sucrose being partially displaced in U.S. industrial food production by HFCS and other non-sucrose natural sweeteners.

Types

Cane

Main article: Sugarcane
Harvested sugarcane from Venezuela ready for processing

Since the 6th century BC, cane sugar producers have crushed the harvested vegetable material from sugarcane in order to collect and filter the juice. They then treat the liquid (often with lime (calcium oxide)) to remove impurities and then neutralize it. Boiling the juice then allows the sediment to settle to the bottom for dredging out, while the scum rises to the surface for skimming off. In cooling, the liquid crystallizes, usually in the process of stirring, to produce sugar crystals. Centrifuges usually remove the uncrystallized syrup. The producers can then either sell the sugar product for use as is, or process it further to produce lighter grades. The later processing may take place in another factory in another country.

Sugarcane is a major component of Brazilian agriculture; the country is a top producer of sugarcane products, such as crystallized sugar and ethanol (ethanol fuel). The sucrose found in sugarcane produces ethanol when fermented and distilled. Brazil has implemented ethanol as an alternative fuel on a national scale.[30]

Beet

Sugar beets
Main article: Sugar beet

Beet sugar producers slice the washed beets, then extract the sugar with hot water in a "diffuser". An alkaline solution ("milk of lime" and carbon dioxide from the lime kiln) then serves to precipitate impurities (see carbonatation). After filtration, evaporation concentrates the juice to a content of about 70% solids, and controlled crystallisation extracts the sugar. A centrifuge removes the sugar crystals from the liquid, which gets recycled in the crystalliser stages. When economic constraints prevent the removal of more sugar, the manufacturer discards the remaining liquid, now known as molasses, or sells it on to producers of animal feed.

Sieving the resultant white sugar produces different grades for selling.

Cane versus beet

It is difficult to distinguish between fully refined sugar produced from beet and cane. One way is by isotope analysis of carbon. Cane uses C4 carbon fixation, and beet uses C3 carbon fixation, resulting in a different ratio of 13C and 12C isotopes in the sucrose. Tests are used to detect fraudulent abuse of European Union subsidies or to aid in the detection of adulterated fruit juice.

Sugar cane tolerates hot climates better, but the production of sugar cane needs approximately four times as much water as the production of sugar beet, therefore some countries that traditionally produced cane sugar (such as Egypt) have built new beet sugar factories since about 2008. Some sugar factories process both sugar cane and sugar beets and extend their processing period in that way.

The production of sugar leaves residues that differ substantially depending on the raw materials used and on the place of production. While cane molasses is often used in food preparation, humans find molasses from sugar beets unpalatable, and it consequently ends up mostly as industrial fermentation feedstock (for example in alcohol distilleries), or as animal feed. Once dried, either type of molasses can serve as fuel for burning.

Pure beet sugar is difficult to find, so labelled, in the marketplace. Although some brands label their product clearly as "pure cane sugar", beet sugar is almost always labeled simply as sugar or pure sugar. Interviews with the 5 major beet sugar-producing companies revealed that many store brands or "private label" sugar products are pure beet sugar. The lot code can be used to identify the company and the plant from which the sugar came, enabling beet sugar to be identified if the codes are known.[31]

Culinary sugars

Grainy raw sugar
Mill white

Mill white, also called plantation white, crystal sugar or superior sugar is produced from raw sugar. It is exposed to sulfur dioxide during the production to reduce the concentration of color compounds and helps prevent further color development during the crystallization process. Although common to sugarcane-growing areas, this product does not store or ship well. After a few weeks, its impurities tend to promote discoloration and clumping; therefore this type of sugar is generally limited to local consumption.[32]

Blanco directo

Blanco directo, a white sugar common in India and other south Asian countries, is produced by precipitating many impurities out of cane juice using phosphoric acid and calcium hydroxide, similar to the carbonatation technique used in beet sugar refining. Blanco directo is more pure than mill white sugar, but less pure than white refined.

White refined

White refined is the most common form of sugar in North America and Europe. Refined sugar is made by dissolving and purifying raw sugar using phosphoric acid similar to the method used for blanco directo, a carbonatation process involving calcium hydroxide and carbon dioxide, or by various filtration strategies. It is then further purified 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 and comes in various crystal sizes for home and industrial use:

White refined granulated sugar for table use
Brown sugar crystals

Brown sugar comes either from the late stages of cane sugar refining, when sugar forms fine crystals with significant molasses content, or from coating white refined sugar with a cane molasses syrup (blackstrap molasses). Brown sugar's color and taste becomes stronger with increasing molasses content, as do its moisture-retaining properties. Brown sugars also tend to harden if exposed to the atmosphere, although proper handling can reverse this.

Measurement

Dissolved sugar content

Scientists and the sugar industry use degrees Brix (symbol °Bx), introduced by Adolf Brix, as units of measurement of the mass ratio of dissolved substance to water in a liquid. A 25 °Bx sucrose solution has 25 grams of sucrose per 100 grams of liquid; or, to put it another way, 25 grams of sucrose sugar and 75 grams of water exist in the 100 grams of solution.

The Brix degrees are measured using an infrared sensor. This measurement does not equate to Brix degrees from a density or refractive index measurement, because it will specifically measure dissolved sugar concentration instead of all dissolved solids. When using a refractometer, one should report the result as "refractometric dried substance" (RDS). One might speak of a liquid as having 20 °Bx RDS. This refers to a measure of percent by weight of total dried solids and, although not technically the same as Brix degrees determined through an infrared method, renders an accurate measurement of sucrose content, since sucrose in fact forms the majority of dried solids. The advent of in-line infrared Brix measurement sensors has made measuring the amount of dissolved sugar in products economical using a direct measurement.

Consumption

Main article: History of sugar

Refined sugar was a luxury before the 18th century. It became widely popular in the 18th century, then graduated to becoming a necessary food in the 19th century. This evolution of taste and demand for sugar as an essential food ingredient unleashed major economic and social changes.[20] Eventually, table sugar became sufficiently cheap and common enough to influence standard cuisine and flavored drinks.

Sucrose forms a major element in confectionery and desserts. Cooks use it for sweetening — its fructose component, which has almost double the sweetness of glucose, makes sucrose distinctively sweet in comparison to other carbohydrates.[35] It can also act as a food preservative when used in sufficient concentrations. Sucrose is important to the structure of many foods, including biscuits and cookies, cakes and pies, candy, and ice cream and sorbets. It is a common ingredient in many processed and so-called "junk foods."

Nutritional information

Sugars, granulated [sucrose]
Nutritional value per 100 g (3.5 oz)
Energy 1,620 kJ (390 kcal)
100 g
0 g
0 g
Vitamins
Thiamine (B1)
(0%)

0 mg

Riboflavin (B2)
(0%)

0 mg

Niacin (B3)
(0%)

0 mg

Vitamin C
(0%)

0 mg

Minerals
Iron
(0%)

0 mg

Phosphorus
(0%)

0 mg

Potassium
(0%)

2.0 mg

Link to USDA Database entry
Percentages are roughly approximated using US recommendations for adults.
Source: USDA Nutrient Database

Refined sugar is 99.9% sucrose, therefore providing only carbohydrate value as a major dietary nutrient and 390 kilocalories per 100 g serving (USDA data, right table).[36] There are no micronutrients having significant content (right table).[36]

Metabolism of sucrose

Granulated sucrose

In humans and other mammals, sucrose is broken down into its constituent monosaccharides, glucose and fructose, by sucrase or isomaltase glycoside hydrolases, which are located in the membrane of the microvilli lining the duodenum.[37][38] The resulting glucose and fructose molecules are then rapidly absorbed into the bloodstream. In bacteria and some animals, sucrose is digested by the enzyme invertase.

Sucrose is an easily assimilated macronutrient that provides a quick source of energy, provoking a rapid rise in blood glucose upon ingestion. Sucrose, as a pure carbohydrate, has an energy content of 3.94 kilocalories per gram (or 17 kilojoules per gram).

Overconsumption of sucrose has been linked with adverse health effects.

Dental caries or tooth decay may be caused by oral bacteria converting sugars, including sucrose, from food into acids that corrodes tooth enamel.

When large amounts of refined food that contain high percentages of sucrose are consumed, beneficial nutrients can be displaced from the diet, which can contribute to an increased risk for chronic disease. The rapidity with which sucrose raises blood glucose can cause problems for people suffering from defective glucose metabolism, such as persons with hypoglycemia or diabetes mellitus.

Sucrose can contribute to the development of metabolic syndrome.[39] In an experiment with rats that were fed a diet one-third of which was sucrose, the sucrose first elevated blood levels of triglycerides, which induced visceral fat and ultimately resulted in insulin resistance.[40] Another study found that rats fed sucrose-rich diets developed high triglycerides, hyperglycemia, and insulin resistance.[41] A 2004 study recommended that the consumption of sucrose-containing drinks should be limited due to the growing number of people with obesity and insulin resistance.[42]

Human health

Human beings have long sought sugars, but aside from wild honey and fruits, have not had access to the large quantities that characterize the modern diet. Studies have indicated potential links between consumption of free sugars including sucrose (particularly prevalent in processed foods) and health hazards, including obesity and tooth decay.[43][44] It is also considered as a source of endogenous glycation processes since it metabolises into glucose and fructose in the body.

Tooth decay

Tooth decay (dental caries) has become a prominent health hazard associated with the consumption of sugars, especially sucrose. Oral bacteria such as Streptococcus mutans live in dental plaque and metabolize any sugars (not just sucrose, but also glucose, lactose, fructose, and cooked starches[45]) into lactic acid. The resultant lactic acid lowers the pH of the tooth's surface, stripping it of minerals in the process known as tooth decay.[46][47]

All 6-carbon sugars and disaccharides based on 6-carbon sugars can be converted by dental plaque bacteria into acid that demineralizes teeth, but sucrose may be uniquely useful to Streptococcus sanguinis (formerly Streptococcus sanguis) and Streptococcus mutans.[48][49] Sucrose is the only dietary sugar that can be converted to sticky glucans (dextran-like polysaccharides) by extracellular enzymes. These glucans allow the bacteria to adhere to the tooth surface and to build up thick layers of plaque. The anaerobic conditions deep in the plaque encourage the formation of acids, which leads to carious lesions. Thus, sucrose could enable S. mutans, S. sanguinis and many other species of bacteria to adhere strongly and resist removal, e.g. by flow of saliva (although they are easily removed by brushing). The glucans and levans (fructose polysaccharides) produced by the plaque bacteria also act as a reserve food supply for the bacteria. Such a special role of sucrose in the formation of tooth decay is much more significant in light of the almost universal use of sucrose as the most desirable sweetening agent. Widespread replacement of sucrose by high-fructose corn syrup (HFCS) has not diminished the danger from sucrose. If smaller amounts of sucrose are present in the diet, they will still be sufficient for the development of thick, anaerobic plaque and plaque bacteria will metabolise other sugars in the diet,[49] such as the glucose and fructose in HFCS.

Glycemic index

Sucrose is a disaccharide made up of 50% glucose and 50% fructose and has a glycemic index of 65.[50] Sucrose is digested rapidly,[51][52] but has a relatively low glycemic index due to its content of fructose, which has a minimal effect on blood glucose.[51]

As with other sugars, sucrose is digested into its components via the enzyme sucrase to glucose (blood sugar) and fructose. The glucose component is transported into the blood (90%) and excess glucose is converted to temporary storage in the liver – named glycogen. The fructose is either bonded to cellulose and transported out the GI tract or processed by the liver into citrates, aldehydes, and, for the most part, lipid droplets (fat).

As the glycemic index measures the speed at which glucose is released into the bloodstream a refined sugar containing glucose is considered high-glycemic. As with other sugars, over-consumption may cause an increase in blood sugar levels from a normal 90 mg/dL to up over 150 mg/dL.[53] (5 mmol/l to over 8.3 mmol/l).

Diabetes mellitus

Diabetes mellitus, a disease that causes the body to metabolize sugar poorly, occurs when either:

  1. the body attacks the cells producing insulin, the hormone that allows the metabolizing of sugar (Type 1 diabetes)
  2. the body's cells exhibit impaired responses to insulin (Type 2 diabetes).

When glucose builds up in the bloodstream, it can cause two problems:

  1. in the short term, cells become starved for energy because they do not have access to the glucose
  2. in the long term, frequent glucose build-up increases the acidity of the blood, damaging many of the body's organs, including the eyes, kidneys, nerves, and/or heart.

Authorities advise diabetics to avoid sugar-rich foods to prevent adverse reactions.[54]

Obesity

The National Health and Nutrition Examination Survey I and their follow-on studies as part of a series indicate that the population in the United States has increased its proportion of energy consumption from carbohydrates and decreased its proportion from total fat while obesity has increased. This implies, along with the United Nations report cited below, that obesity may correlate better with sugar consumption than with fat consumption, and that reducing fat consumption while increasing sugar consumption may increase the level of obesity. The following table summarizes this study (based on the proportion of energy intake from different food sources for US Adults 20–74 years old, as carried out by the U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Health Statistics, Hyattsville, MD[55]):

Year Sex Carbohydrate Fat Protein Obesity
1971 Male 42.4% 36.9% 16.5% 12.1%
1971 Female 45.4% 36.1% 16.9% 16.6%
2000 Male 49.0% 32.8% 15.5% 27.7%
2000 Female 51.6% 32.8% 15.1% 34.0%

Added sugar is not always evident in food products. While expected in desserts, candies, and soft drinks, it is also added to a wide range of non-sweet items such as bread, crackers, potato chips, peanut butter, soup, salad dressing, ketchup, mayonnaise, and many other common sauces. Forms of added sugar include technically accurate, but misleading, terms such as cane juice, evaporated cane juice, corn syrup and corn syrup solids, malt syrup, rice syrup, dextrose, maltose, maltodextrin, molasses, treacle, and xylose.[56]

A 2002 study conducted by the U.S. National Academy of Sciences concluded that, due to discrepancies in data from different studies, it could not set a tolerable upper intake level, since "there is no clear and consistent association between increased intakes of added sugars and BMI." However, it explains that this may be due to the underreporting of the consumption of added sugars. (BMI, or "body mass index," is a measure of weight and height used to estimate body fat.)[57]

Gout

The occurrence of gout is connected with an excess production of uric acid. A diet rich in sucrose may lead to gout as it raises the level of insulin, which prevents excretion of uric acid from the body. As the concentration of uric acid in the body increases, so does the concentration of uric acid in the joint liquid and beyond a critical concentration, the uric acid begins to precipitate into crystals. Researchers have implicated sugary drinks high in fructose in a surge in cases of gout.[58][59]

Sucrose intolerance

Main article: sucrose intolerance

UN dietary recommendation

In 2015, the World Health Organization (WHO) published a new guideline on sugars intake for adults and children, as a result of an extensive review of the available scientific evidence by a multidisciplinary group of experts. The guideline recommends that both adults and children reduce the intake of free sugars (monosaccharides and disaccharides added to foods and beverages by the manufacturer, cook or consumer, and sugars naturally present in honey, syrups, fruit juices and fruit juice concentrates) to less than 10% of total energy intake. A reduction to below 5% of total energy intake brings additional health benefits, especially in what regards dental caries. [60]

Religious concerns

The sugar refining industry often uses bone char (calcinated animal bones) for decolorizing.[61][62] About 25% of sugar produced in the U.S. is processed using bone char as a filter, the remainder being processed with activated carbon. As bone char does not seem to remain in finished sugar, Jewish religious leaders consider sugar filtered through it to be pareve and therefore kosher.[62]

Trade and economics

One of the most widely traded commodities in the world throughout history, sugar accounts for around 2% of the global dry cargo market. International sugar prices show great volatility, ranging from around 3 to over 60 cents per pound in the past 50 years. About 100 of the world's 180 countries produce sugar from beet or cane, a few more refine raw sugar to produce white sugar, and all countries consume sugar. Consumption of sugar ranges from around 3 kilograms per person per annum in Ethiopia to around 40 kg/person/yr in Belgium. Consumption per capita rises with income per capita until it reaches a plateau of around 35 kg per person per year in middle income countries.

Many countries subsidize sugar production heavily. The European Union, the United States, Japan, and many developing countries subsidize domestic production and maintain high tariffs on imports. Sugar prices in these countries have often exceeded prices on the international market by up to three times; today, with world market sugar futures prices currently strong, such prices typically exceed world prices by two times.

World raw sugar price from 1960 to 2014
World raw sugar price from 1960 to 2014

Within international trade bodies, especially in the World Trade Organization, the "G20" countries led by Brazil have long argued that, because these sugar markets in essence exclude cane sugar imports, the G20 sugar producers receive lower prices than they would under free trade. While both the European Union and United States maintain trade agreements whereby certain developing and less developed countries (LDCs) can sell certain quantities of sugar into their markets, free of the usual import tariffs, countries outside these preferred trade régimes have complained that these arrangements violate the "most favoured nation" principle of international trade. This has led to numerous tariffs and levies in the past.

In 2004, the WTO sided with a group of cane sugar exporting nations (led by Brazil and Australia) and ruled the EU sugar-régime and the accompanying ACP-EU Sugar Protocol (whereby a group of African, Caribbean, and Pacific countries receive preferential access to the European sugar market) illegal.[63] In response to this and to other rulings of the WTO, and owing to internal pressures on the EU sugar-régime, the European Commission proposed on 22 June 2005 a radical reform of the EU sugar-régime, cutting prices by 39% and eliminating all EU sugar exports.[64] The African, Caribbean, Pacific and least developed country sugar exporters reacted with dismay to the EU sugar proposals.[65] On 25 November 2005, the Council of the EU agreed to cut EU sugar prices by 36% as from 2009. In 2007, it seemed[66] that the U.S. Sugar Program could become the next target for reform. However, some commentators expected heavy lobbying from the U.S. sugar industry, which donated $2.7 million to US House and US Senate incumbents in the 2006 US election, more than any other group of US food-growers.[67] Especially prominent lobbyists include The Fanjul Brothers, so-called "sugar barons" who made the single largest individual contributions of soft money to both the Democratic and Republican parties in the political system of the United States of America.[68][69]

Small quantities of sugar, especially specialty grades of sugar, reach the market as 'fair trade' commodities; the fair trade system produces and sells these products with the understanding that a larger-than-usual fraction of the revenue will support small farmers in the developing world. However, whilst the Fairtrade Foundation offers a premium of $60.00 per tonne to small farmers for sugar branded as "Fairtrade",[70] government schemes such the U.S. Sugar Program and the ACP Sugar Protocol offer premiums of around $400.00 per tonne above world market prices. However, the EU announced on 14 September 2007 that it had offered "to eliminate all duties and quotas on the import of sugar into the EU".[71]

The US Sugar Association has launched a campaign to promote sugar over artificial substitutes. The Association now aggressively challenges many common beliefs regarding negative side-effects of sugar consumption. The campaign aired a high-profile television commercial during the 2007 Primetime Emmy Awards on FOX Television. The Sugar Association uses the trademark tagline "Sugar: sweet by nature."[72]

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Further reading

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