lactose

1. A disaccharide, C₁₂H₂₂O₁₁, found in milk, that may be hydrolyzed to yield glucose and galactose.
2. A white crystalline substance obtained from whey and used in infant foods, bakery products, confections, and pharmaceuticals as a diluent and excipient. Also called milk sugar.

Milk sugar or 4-O-β-D-galactopyranosyl-D-glucose. This reducing disaccharide is obtained as the α-D anomer (see formula, where the asterisk indicates a reducing group); the melting point is 202°C (396°F). Lactose is found in the milk of

The carbohydrate of milk, sometimes called milk sugar. A disaccharide of glucose and galactose. Used pharmaceutically as a tablet filler and as a medium for growth of micro-organisms. The fermentation of lactose to lactic acid by bacteria is responsible for the souring of milk. Ordinary lactose is α-lactose, which is 16% as sweet as sucrose; if crystallized above 93 °C, it is converted to the β-form which is more soluble and sweeter.

A sugar found in milk. It is a disaccharide made by the combination of galactose and glucose. Milk goes sour because the lactose is converted by bacteria into lactic acid. Lactose is an energy-rich food but some people suffer from lactose intolerance in which the consumption of milk (or other foods containing lactose) causes cramps, flatulence, and diarrhoea.

Lactose intolerance is due to a deficiency in the production of lactase, an enzyme that digests lactose into glucose and galactose. It most often affects people who consume few milk products, but since lactase production tends to reduce with age, a large proportion of the population may suffer some degree of lactose intolerance as they grow older. In fact, most ethnic groups (apart from Caucasians) do not retain lactase past adolescence so most adults are lactose intolerant. A few sufferers can still eat some fermented dairy products, such as buttermilk and yoghurt, or they may be able to obtain lactase-treated products. Others may have to avoid dairy products altogether. These people have to find alternative sources of the nutrients, such as calcium and riboflavin, that they would otherwise obtain from milk or its products.

[LAK-tohs] This sugar occurs naturally in milk and is also called milk sugar. It's the least sweet of all the natural sugars and is used commercially in foods such as baby formulas and candies.

A disaccharide found in the milk of all mammals. Lactose is used as a component of formulas for infants; it is also used as a laxative and a diuretic.

For more information on lactose, visit Britannica.com.

A disaccharide sugar made from galactose and glucose; milk sugar. Although lactose is potentially a rich source of energy, many people suffer from lactose intolerance because they lack the enzyme (lactase) required to digest it.

A sugar derived from milk, which on hydrolysis yields glucose and galactose.

• l. digestion test — oral test of foal's ability to digest milk sugar.
• l. intolerance — inability to digest lactose in the diet because of the lack of the enzyme lactase in the small intestine. Clinical consequences are intestinal discomfort and diarrhea.
• l. tolerance test — a monitor of intestinal epithelial damage, similar to the starch digestion test. The test measures the rise in blood glucose at timed intervals after oral administration of lactose; essentially a test of disaccharidase efficiency of the gut.

Lactose
IUPAC name	4-O-β-D-galactopyranosyl-β-D-glucopyranose
Other names	Milk sugar; (2S,3R,4R,5S,6R)-6-(hydroxymethyl)-5-((2S,3R,4S,5R,6R)-3,4,5-trihydroxy-6-(hydroxymethyl)tetrahydro-2H-pyran-2-yloxy)tetrahydro-2H-pyran-2,3,4-triol
Identifiers
CAS number	[63-42-3]
PubChem	6134
SMILES	O[C@H]2[C@H](O[C@@H]1O[C@H](CO)[C@H](O)[C@H](O)[C@H]1O)[C@@H](CO)O[C@@H](O)[C@@H]2O
Properties
Molecular formula	C12H22O11
Molar mass	342.29648 g/mol
Appearance	white solid
Solubility in water	0.216 g/mL
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references

Lactose (also referred to as milk sugar) is a sugar that is found most notably in milk. Lactose makes up around 2–8% of milk (by weight). The name comes from the Latin word for milk, plus the -ose ending used to name sugars. Its systematic name is β-D-galactopyranosyl-(1↔4)β-D-glucopyranose.

Contents 1 Chemistry 1.1 Solubility 2 Digestion of Lactose (Catabolism) 3 References

Chemistry

Lactose is a disaccharide that consists of β-D-galactose and α/β-D-glucose fragments bonded through a β1-4 glycosidic linkage. As it gives free radicals by mechanochemistry, it is possible to use lactose to follow by ESR (Electron Spin Resonance) the energy used during a milling process.^[1]

Solubility

Lactose has a solubility of 1 in 4.63 measured %w/v. This translates to 0.216 g of lactose dissolving readily in 1 mL of water.

The solubility of lactose in water is 18.9049 g at 25°C, 25.1484 g at 40°C and 37.2149 g at 60°C per 100 g solution. Its solubility in ethanol is 0.0111 g at 40°C and 0.0270 g at 60°C per 100 g solution.^[2]

Digestion of Lactose (Catabolism)

Main article: Lactose intolerance

Infant mammals nurse on their mothers to drink milk, which is rich in the carbohydrate lactose. The intestinal villi secrete an enzyme called lactase (β-D-galactosidase) to digest it. This enzyme cleaves the lactose molecule into its two subunits, the simple sugars glucose and galactose, which can be absorbed.

Since lactose occurs mostly in milk, in most mammals the production of lactase gradually decreases with maturity due to a lack of constant consumption.

Many people with ancestry in Europe, the Middle East, India, and parts of East Africa maintain lactase production into adulthood. In many of these areas, milk from mammals such as cattle, goats, and sheep is used as a large source of food. Hence, it was in these regions that genes for lifelong lactase production first evolved. The genes of lactose tolerance have evolved independently in various ethnic groups.

People who are not lactose tolerant may suffer uncomfortable or socially unacceptable symptoms of too much lactose consumption. In these people, lactose is not broken down and provides food for gas-producing gut flora. This can lead to bloating, flatulence, and other gastrointestinal symptoms.^[3]

References

1. ^ Baron M., Chamayou, A., Marchioro L., Raffi J., Adv. Powder Technol., 2005, 16, 3, 199-212.
2. ^ Machado, José J.B.; João A. Coutinho, Eugénia A. Macedo (20001) (PDF). Solid–liquid equilibrium of a-lactose in ethanol/water. Fluid Phase Equilibria. http://path.web.ua.pt/file/FPE%20(2000)%20173%20121.pdf. Retrieved on 2007-12-05. 
3. ^ Nicholas Wade (December 10, 2006). "Study Detects Recent Instance of Human Evolution". The New York Times. http://www.nytimes.com/2006/12/10/science/10cnd-evolve.html?. Retrieved on 2007-12-05. 

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Dansk (Danish)
n. - laktose, mælkesukker

Nederlands (Dutch)
lactose (melksuiker)

Français (French)
n. - lactose

Deutsch (German)
n. - (Chem.) Lactose, Milchzucker

Ελληνική (Greek)
n. - λακτόζη, γαλακτοσάκχαρο

Italiano (Italian)
lattosio

Português (Portuguese)
n. - lactose (f) (Quím.)

Русский (Russian)
лактоза

Español (Spanish)
n. - lactosa

Svenska (Swedish)
n. - laktos, mjölksocker

中文（简体）(Chinese (Simplified))
乳糖

中文（繁體）(Chinese (Traditional))
n. - 乳糖

한국어 (Korean)
n. - 유당

日本語 (Japanese)
n. - ラクトース

العربيه (Arabic)
‏(الاسم) اللكتوز, سكر اللبن‏

עברית (Hebrew)
n. - ‮סוכר חלב, לקטוז‬

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