Maltose: Structure, Properties, Uses and Sample Questions

Two glucose molecules are combined to form maltose, a disaccharide. Other names for it include Cextromaltose, Maltobiose, Maltodiose, and D-Maltose. This sugar is white in color. Reduced sugars. Maltose, its properties, uses, and some of the previous years' questions asked on this topic will be discussed in this article.

What is Maltose?

Two units of *-D-glucose are linked by a glycosidic linkage to form maltose. In this example, glucose units are linked by their first and fourth carbons (i.e. the first carbon of one glucose unit and the fourth carbon of another glucose unit). At the 1st carbon of the second glucose unit, an aldehyde group is formed. Because maltose contains a free aldehyde group, it is a reducing sugar.

Formula and Structure of Maltose

As mentioned above, maltose is a disaccharide composed of two *-D-glucose units, and its formula is: C12H22O11

Structure of Maltose (C12H22O11) –

Production of Maltose

Malt is the source of the word maltose. In order to distinguish maltose from sugar, a biochemical series of glucose chains, 'ose' was added. The enzyme diastase is used to hydrolyze starch into maltose. Starch is also broken down into glucose molecules by heating it in a strong acid for several minutes. Maltase is an enzyme that is found in living organisms.

Description of maltose

Due to the presence of a free aldehyde group in one of its glucose units, maltose is a reducing sugar.
White crystals or powders of maltose can be found.
Carbon dioxide, water, and sulfur dioxide are produced when maltose reacts with sulphuric acid:

C12H22O11 + 24H2SO4 → 12CO2 + 35H2O + 24SO2

During the hydrolysis of maltose, ethanol and carbon dioxide are produced:

C12H22O11 + H2O → 4C2H5OH + 4CO2

Maltose is hydrolyzed into glucose by the maltase enzyme:

C12H22O11 + H2O → 2C12H22O11

Some other properties of maltose -

Molar mass: 342.297 g.mol-1
Density: 1.54 g.cm-3
Solubility in Water: 1.080 g/mL (at 20 °C)
Melting Point: 160-165 °C
Chiral Rotation: +140.7° [α]D
Odour: No odour
Heat Capacity: 298.15K
Taste: Sweet taste (30 – 60% as sweet as sugar)
Detection Test: Woehik test or Fearon’s test

Uses of Maltose

Corn syrup contains maltose, which is a cheap source of sugar.
For making beer, maltose is used in the malting process of barley, the malting process adds sweetness to the beer.
Its caramel-like taste makes it useful in bakeries, soft drinks, sweets, alcoholic beverages, infant formula, and sugar-free products.
Maltose is produced during seed germination by an enzyme called amylase, which hydrolyzes starch into disaccharide for new plants.
Amylase converts starch into maltose during digestion, and the secreted enzyme maltase converts maltose into glucose, which is either utilized by the body or stored in the liver as glycogen.

Differences in Sucrose, Lactose, and Maltose Structures

Glucose units make up the disaccharides sucrose, lactose, and maltose. According to their structure, they differ from each other:

maltose is made up of two glucose molecules.
The sugar sucrose is formed when a molecule of fructose and a molecule of glucose combine.
Galactose and glucose combine to form lactose.

Maltose and cellobiose are different sugars.

Cellobiose and maltose are both made up of glucose, which are linked by C1 for one and C4 for the other. Cellobiose, on the other hand, has the beta anomer of glucose as the first glucose unit, whereas maltose has the alpha anomer of glucose as the first glucose unit.

Things to Remember based on Maltose

Maltose is a disaccharide that consists of two units of α-D-glucose.

In maltose, each unit of glucose is linked by a glycosidic bond.
The formula of maltose is : C12H22O11
A free aldehydic group in maltose makes it a reducing sugar.
Maltose can be detected using Fehling's solution and Tollen's reagent test.
It is used in the preparation of beer and sugar-free products due to its low sugar content.
In the germination and digestion process, maltose plays an important role.

Previous Years’ Questions based on Maltose

Ques. Name the product formed during the hydrolysis of maltose? [All India 2014] 1 mark

Ans. Maltose on hydrolysis in the presence of maltase forms two molecules of glucose.

C12H22O11 + H2O → 2C12H22O11

Ques. Give an example of reducing and non-reducing sugars. [Delhi 2010C] 2 marks

Ans. Reducing sugar: Maltose or Lactose,

Non-reducing sugar: Sucrose.

Ques. What is glycosidic linkage? [Delhi 2013, All India 2011C, 2008] 2 marks

Ans. When two monosaccharide units are joined together, an oxide linkage is formed by the loss of a water molecule. This linkage between two monosaccharide units through an oxygen atom is called glycosidic linkage.

Ques. What is essentially the difference between the α-form of glucose and the β-form of glucose? Explain.

Ans. Glucose is found to exist in two different crystalline forms which are named α and β. The two forms differ from each other in the orientation of the -OH group at C-1. Moreover, the α-form is obtained by crystallization from a concentrated solution of glucose at 303K while the β-form is obtained by crystallization from hot and saturated solution at 371K.

Ques. How can reducing and non-reducing sugars be distinguished? Mention the structural features characterizing reducing sugars.

Ans. Reducing sugars- The sugars which reduce Fehling’s solution and Tollen’s reagent are called reducing sugars, e.g. all monosaccharides containing free aldehyde or ketone groups are reducing sugars. So, the presence of a free aldehyde or ketone group is the main feature of reducing sugars.

Non-reducing sugars- The sugars which do not reduce Fehling’s solution or Tollen’s reagent are called non-reducing sugars, e.g. sucrose. In non-reducing sugars, reducing groups of monosaccharides, i.e. aldehydic or ketonic groups are bonded.

Ques. Name the products of hydrolysis of lactose.

Ans. On hydrolysis with dilute acids, lactose gives an equimolar mixture of D-glucose and D-galactose.