Identification of Carbohydrates with an Iodine Test

Identification of Carbohydrates with an Iodine Test

Purpose:

Prove the existence of polysaccharides such as starch, glycogen and dextrin.

        

Principle:

Polysaccharide by the addition of iodine to produced a specific color. Starch will produce a blue color with the addition of iodine, dextrin produce red wines with iodine, while the glycogen (erytro-dextrin) will produce a dark red or reddish-brown color with the addition of iodine.

Basic theory:

Polysaccharide molecules typically have larger and more complex than the monosaccharide and oligosaccharides. Polysaccharide molecule consisted of many monosaccharide molecules.

Polysaccharide consisting of only one kind of monosaccharide called homo-polysaccharide, whereas other compounds containing called hetero-polysaccharide.

Polysaccharides are generally in the form of white compound and do not form crystals, did not have a sweet taste and has no reducing properties, a polysaccharide that can dissolve in water will form a colloidal solution.

Tools:

1.     Porcelain Drip

2.     Pipette Drops

3.     Rack Tube

4.     Label

Materials:

1.     Starch 2%

2.     Dextrin 1%

3.     Gelatin 2%

4.     Glucose 1%

5.     Lactose 1%

6.     Iodine Solution

Procedure:

1.     Porcelain drip provide clean and dry.

2.     Give label at a porcelain drip.

3.     Enter three drops of test solution into a porcelain drip.

4.     First plate, fill with three drops of starch 2%.

5.     Second plate, fill with three drops of dextrin 1%.

6.     Third plate, fill with three drops of gelatin 2%

7.     Fourth plate, fill with three drops of glucose 1%.

8.     And fifth plate, fill with three drops of lactose 1%.

9.     And the next, add two drops of iodine solution to each plate.

10.                        See the result, observe specific color formed.

The Observation:

Test Solution	Result of Iodine Test	Polysaccharide (+/-)
Starch 2%	Solution colored blue until dark blue	+
Dextrin 1%	Solution colored red wine	+
Gelatin 2%	Solution colored yellow	_
Glucose 1%	Solution colored yellow	_
Lactose 1%	Solution colored yellow	_

Discussion:

Containing polysaccharides are starch and dextrin. Because it can react with an Iodine reagent to formed a specific color (blue and red wine).

Conclusion:       

From the experiment results above, the substance of containing polysaccharide is starch and dextrin.