Lactose is a disaccharide sugar derived from galactose and glucose that is found in milk. It makes up around 2–8% of milk (by weight), although the amount varies among species and individuals, and milk with a reduced amount of lactose also exists. It is extracted from sweet or sour whey. The name comes from lac or lactis, the Latin word for milk, plus the -ose ending used to name sugars. It has a formula of C12H22O11 and the hydrate formula C12·11H2O, making it an isomer of sucrose.
Lactose is a disaccharide derived from the condensation of galactose and glucose, which form a β-1→4 glycosidic linkage. Its systematic name is β-D-galactopyranosyl-(1→4)-D-glucose. The glucose can be in either the α-pyranose form or the β-pyranose form, whereas the galactose can only have the β-pyranose form: hence α- and β-lactose refer to the anomeric form of the glucopyranose ring alone. It is hydrolysed to glucose and galactose, isomerised in alkaline solution to lactulose, and catalytically hydrogenated to the corresponding polyhydric alcohol, lactitol. Lactose monohydrate crystals have a characteristic tomahawk shape that can be observed with a light microscope.
Several million tons are produced annually as a by-product of the dairy industry. Whey is made up of 6.5% solids of which 4.8% is lactose that may be purified by crystallisation. Whey or milk plasma is the liquid remaining after milk is curdled and strained, for example in the production of cheese. It makes up about 2–8% of milk by weight. Industrially, it is produced from whey permeate – that is whey filtrated for all major proteins. The protein fraction is used in infant nutrition and sport nutrition while the permeate can be evaporated to 60–65% solids and crystallized while cooling. It can also be precipitated from whey using ethanol. Since it is insoluble in ethanol, it precipitates, in about 65% yield.
Source: Wikipedia
Lactose
Chromatogram(s) using Benson Polymeric Columns
Part No.:
Eluent:
Flow Rate:
Detection:
Temperature:
Sample Size:
Column Size:
Resin Type:
DI H2O
0.6 ml/min
RI
85 C
20 ul, 30 mg/ml
300 x 7.8 mm
8% Pb
2 – Glucose
3 – Galactose
4 – Fructose
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