Carbohydrate Test

1. Molish test

In a carbohydrate known some testing to determine the content contained in these carbohydrates. One of the tests conducted to determine the presence or absence of carbohydrates is the Molisch test. When there are several solutions that are not known for certain that the solution contains carbohydrates or not, this test can be performed to determine the carbohydrate content.

Solution of a positive reaction will give a purple ring when direksikan with Naphthols and concentrated sulfuric acid. It is estimated, the concentration of concentrated sulfuric acid acts as an agent acting on sugar dehydration to form furfural and its derivatives are then combined with Naphthols to form a colored product.

2. Iodine test

Test or tests are used to separate the starch contained in the solution. Positive reaction is characterized by a change in color to blue. The resulting blue color is thought to result from the complex bond between starch with iodine. When starch that has been poured iodine and then heated, the color produced as a result of a positive reaction will disappear.

And when cooled will re-appear in blue. In the starch itself consists of two kinds of starch that is amylose is not soluble in cold water and amylopectin is soluble in cold water. When starch dissolved in water, amylose will form micelles which molecules are clustered and are not visible because it is only at the molecular level.

These micelles can bind I2 contained in the reagent iodine and gives a distinctive blue color of the solution being tested. At the time of heating, the molecules repel each other so that micellespun will no longer be formed so that no longer bind to I2. As a result the typical blue color is caused to disappear.

Micelles will be formed again when cooled and re-emerged khaspun blue. Characteristic blue color caused as a result of positive reaction, will also be lost if the solution that has been positive in testing with iodine added NaOH. Na + ions that is alkaline will bind iodine so that the typical blue color will fade and disappear.

3. Experiment Benedict

Benedict test aims to determine the reducing sugar in a solution with the indicator changes color to red brick in particular. Benedict's reagent is used to test or examine the presence of reducing sugars in a liquid.

Monosaccharides that are redutor, with diteteskannya reagent will cause the brick red precipitate. In addition to testing the existence of reducing sugars, is also true in quantitative, as more and more sugar in solution, then the darker color of the sediment.

4. Fermentation experiments

Percobaaan fermentation conducted to determine the sugar that can be fermented. In this experiment, after a carbohydrate solution added to the suspension of yeast and aged for 1 hour in vitro fermentation, CO2 bubbles appear in the solution. In addition to CO2 bubbles appear, the solution can be kissed by the smell of alcohol. This situation indicates that the carbohydrate groups that can contain sugars that can be fermented.

5. Test Seliwanoff

Some carbs have a ketone group, a ketone group can be determined through testing seliwanoff. If the carbohydrate-containing ketone group is reacted with seliwanoff will show a red color as a positive reaction.

The presence of red color is the result of condensation of resorcinol which is preceded by the formation of hydroxy methyl furfural. The process of formation of hydroxy methyl furfural comes from the conversion of fructose by acid hot klorik who then produce acids and hydroxy methyl furfural livulenik.