Components of Food Class 6 Science - Test for Starch, Protein and Fats

Components of Food Class 6 Science - Test for Starch, Protein and Fats
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We all need food for energy, growth and maintenance. We obtain food from plants and animals. Food must contain required quantity of carbohydrates, proteins, fats, vitamins, minerals, dietary fibres and water.
Test for starch:
Take a dilute solution of iodine for the test. Take small quantity of food item in a glass bowl. With the help of dropper we will put 2-3 drops of dilute iodine solution to it. If the color of the food turns blue-black then it means that food contains starch. However if blue-black color is not observed then it means that food does not contain starch.
Test for Protein
To test if the food contains proteins or not we need to prepare a solution of copper sulphate. For that we will mix about 2 g of copper sulphate powder in 100 ml of water. We need to stir the solution well so as to have proper mixing of the powder. In similar way we also prepare a solution of 10 g of caustic soda in 100 ml of water.
To carry out the test we need the the food in the form of paste. We then add a drop of copper sulphate solution and about few drops of solution of caustic soda into the test tube. Check if there is change in color! If not add one more drop of copper sulphate solution and few drops of caustic soda solution. If you observe violet color of the mixture then it means that proteins are present in the food. Test for fats.
If we put a drop of oil on a paper then it becomes partially transparent. Take food sample on a filter paper. Fold the paper and crush food sample present in it. You may see a stain on the paper. Let the paper dry for some time so that if the food sample contain water then it get evaporated. Now observe the stain. If the stain is translucent then it means that food contain fats.