Test for Carbohydrate, Proteins and Fats – MeitY OLabs

Test for Carbohydrate, Proteins and Fats – MeitY OLabs

November 5, 2019 17 By Ewald Bahringer


Test for Carbohydrate, Proteins and Fats The food we eat is one of the necessary factors
in our daily life that provides nutritional support for the human body. Food consists
of both organic and inorganic substances. Carbohydrates, fats and proteins are the main
organic substances present in food and provide energy. In this video, we learn how to test
for the presence of carbohydrates, proteins and fats in food substances. Test for Carbohydrates One of the main components of our diet is
carbohydrates. Glucose, sucrose and starch are all forms of carbohydrates found in our
daily food. Let’s start with testing for the presence
of glucose in food substances. There are two tests, Benedict’s and Fehling’s test,
used to find if glucose is present. Benedict’s Test Materials Required: Banana extract in a test tube, Benedict’s
reagent, burner, test tube holder and a dropper. Procedure: Using a dropper, take a small quantity of
Benedict’s reagent. Add the reagent to the test tube containing
banana extract. Boil the sample over a burner for 2 minutes
holding the test tube firmly with a test tube holder.
Keep shaking the test tube as it is being heated.
A brick red precipitate appears, indicating the presence of glucose in the banana extract. Conclusion: On boiling banana extract with the Benedict’s
reagent, the cupric ion present in the Benedict’s reagent is reduced by the reducing agent,
sugar, to form a brick red coloured precipitate of cuprous oxide. Fehling’s Test Materials Required: Banana extract in a test tube, test tube holder,
Fehling’s solution A, Fehling’s solution B, dropper and a burner. Procedure: Using a dropper, take a small quantity of
Fehling’s solution A. Add the Fehling’s solution A to the test tube
containing banana extract. Using a dropper, take a small quantity of
Fehling’s solution B. Add Fehling’s solution B to the test tube
containing banana extract. Boil the sample over a burner for 2 minutes,
holding the test tube firmly with a test tube holder.
Keep shaking the test tube while heating. A brick red precipitate appears, indicating
the presence of glucose in the banana extract. Conclusion: The cupric ion present in the Fehling’s solution
is reduced on boiling by the reducing substance, sugar, to form the brick red coloured precipitate
of cuprous oxide. Now we can test the presence of sucrose in
food substances. Materials Required: Sugarcane extract in a test tube, concentrated
HCl, NaOH solution, Benedict’s reagent, test tube holder and a dropper. Procedure: Using a dropper, take a small quantity of
concentrated HCl. Add 2 to 3 drops of concentrated HCl to the
test tube containing sugarcane extract. Boil the sample over a burner for 2 minutes,
holding the test tube firmly with a test tube holder.
This hydrolyses sucrose into glucose and fructose. Using a dropper, take a small quantity of
NaOH solution. Add few drops of NaOH solution to the test
tube to make the solution alkaline. Now we can perform Benedict’s test to this
solution to test for the presence of glucose. Using a dropper, take a small quantity of
Benedict’s reagent. Add the reagent to the test tube containing
the sample. Boil the sample over a burner for 2 minutes,
holding the test tube firmly with a test tube holder.
The colour changes from blue to green and finally to orange or brick red, indicating
the presence of glucose. Let’s test for the presence of starch in food
substances. Materials required Potato extract in a test tube, iodine solution
and a dropper. Procedure
Using a dropper, take a small quantity of iodine solution.
Add 5 drops of iodine solution to the test tube containing potato extract.
Blue black colour indicates the presence of starch in potato extract. Test For Proteins Proteins are large biological molecules made
up of large number of amino acid units. The tests that are used to conduct for the presence
of proteins in food substances are Biuret test, Xanthoproteic test and Million’s test. Biuret Test Materials Required Egg albumin in a test tube, 40% NaOH solution,
1% CuSO4, test tube holder and a dropper. Procedure Using a dropper, take a small quantity of
40% NaOH solution. Add a few drops of NaOH solution to the test
tube containing egg albumin. Using a dropper, take a small quantity of
1% CuSO4 solution. Add 2-3 drops of CuSO4 solution to the test
tube containing egg albumin. Shake the solution to mix it well.
A violet colour appears in the test tube, which indicates the presence of proteins. Xanthoproteic Test Materials required Egg albumin in a test tube, concentrated HNO3,
ammonia solution, test tube holder and a dropper. Procedure Using a dropper, take a small quantity of
concentrated HNO3. Add 5 drops of Concentrated HNO3 to the test
tube containing egg albumin. Boil the sample over a burner for 2 minutes,
holding the test tube firmly with a test tube holder. Yellow precipitate appears in the
test tube. Using a dropper, take a small quantity of
ammonia solution. Add a few drops of ammonia solution to the
sample. Shake the solution to mix it well.
Yellow ppt. changes to orange in colour, which indicates the presence of protein. Million’s Test Materials Required Egg albumin in a test tube, Million’s reagent
and a dropper. Procedure Using a dropper, take a small quantity of
Million’s regent. Add few drops of Million’s reagent to the
test tube containing egg albumin. Wait for some time.
Pink colour appears in the test tube, which indicates the presence of protein. Test for Fats Fats are complex molecules made up of fatty
acids and glycerol. They are found stored in many oil seeds and some animal tissues.
The tests that are used to conduct for the presence of fats in food substances is Sudan III test. Materials Required: Oil in a test tube, Sudan III solution and
a dropper. Procedure: Using a dropper, take a small quantity of
Sudan III reagent. Add few drops of Sudan III reagent to the
test tube containing egg albumin. Shake the solution to mix it well.
Pink droplets appear indicating the presence of fat in the sample.
Paper Spot Test Materials Required: Peanut seeds and piece of white paper. Procedure: Take a peanut seed from the watch glass.
Crush the peanut seed and rub it on a piece of white paper.
Paper becomes translucent at the spot, which indicates the presence of fat.