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Food Tests For Energy Nutrients |
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Testing foods for the presence of protein, fat and carbohydrates may be done by using special chemical solutions. Such experiments should only be carried out in a laboratory. There are different tests for energy nutrients which are listed below.
Tests for Carbohydrates: Starch
Iodine solution is used to test for starch. Heat the food to be tested, (e.g. starch powder, potato, flour, ground rice) in water and boil to cook the starch. When cool, add a few drops of Iodine solution. A dark blue color means starch is present.
Tests for Carbohydrates: Glucose
Benedict's solution is used for glucose testing. First of all boil the food to be tested in a test tube with a little of Benedict's solution. Take care as it may boil out of the tube. If glucose is present, then the mixture will change from clear blue to opaque green, then to yellow, then to brick red.
Test for Fat
Ethanol is used for a fat test. Place the food (like cooking oil, egg yolk, finely granted cheese, crushed nut) to be tested in a clean, dry test tube with some ethanol (2 drops of oil to 5 cm3 of ethanol). Shake thoroughly to dissolve the fat, and then pour the solution into another test tube containing a little water. A cloudy white emulsion indicates the presence of fat.
Test for Protein
The Biuret test is used for the analysis of protein in food. Use liquid food for testing (e.g. milk, egg white, cheese liquidized with water), and place in test tube. Add an equal volume of sodium hydroxide (2 molar) with 1 drop of copper sulfate (0.1 molar) and make a solution. A mauve color develops if protein is present.
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