Test For Starch, Proteins and Fats


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Nutrition is the way in which an organism obtains its food and how it is used in the body to get energy. Food we eat should have the substances that are required by our body to carry out normal functions. These substances are called as nutrients.

Nutrients are nourishing components of food that are required by our body. They release energy and help in body growth. Nutrients found in our food are carbohydrates, proteins, fats, vitamins and minerals. Food also contains dietary fibres and water. Different types of food contain two or more nutrients in combination.
  • Energy-giving food: Carbohydrates and fats are called as energy-giving food. Carbohydrates provide us instant energy. Fats are stored energy resources.
  • Body-building food: Proteins are considered to be body-building food as they help in body growth and repair of damaged parts of the body.
  • Protective food: Vitamins and minerals are considered to be protective food as they protect us from many dieases. They give us resistance against disease causing germs.

a) Carbohydrates: Carbohydrates provide instant energy to us. Carbohydrates in our food are of three types, sugar, starch and cellulose.
  • Sugar is the sweet substance. Glucose is the instant sugar.
  • Fructose is available in fruits and is called as fruit sugar. Sugar is also present in honey.
  • Common sugar we use is sucrose. It is made from sugarcane.
  • Lactose is also a sugar present in milk. Hence, it is called as milk sugar.
  • Starch is present in grains like rice, wheat, maize, tubers like potatoes etc.
  • Cellulose is also a form of carbohydrate which cannot be digested by human beings. It can be digested by grass-eating animals. Cellulose forms the bulk in our food.

Test to confirm the presence of carbohydrate (starch)
The following steps are performed to test the presence of starch in a food item.
  • Take small quantity of the food item to be tested on a porcelain tile.
  • Dilute it with two drops of water.
  • Put 2-3 drops of iodine solution on it.
  • Observe the colour of the food item.
  • Change of colour in the food item into blue-black indicates the presence of starch in the food item.

b) Proteins: Proteins are the substances which help us in growth of our body.
  • Proteins help in healing of wounds. Proteins also help in repair of damaged parts in the body.
  • When our body does not receive any carbohydrates and fats to release energy, proteins can release energy in those special cases.

Test to confirm the presence of protein
The following steps are performed to test the presence of protein in a food item.
  • Take a small quantity of the food item to be tested.
  • Grind the food item and powder it by mashing .
  • Put the food item into a test tube.
  • Add 10 drops of water into the same test tube.
  • Add two drops of copper sulphate solution to the same test tube.
  • Add 10 drops of caustic soda solution and shake the same test tube.
  • Observe the colour of the mixture.
  • Violet colour indicates the presence of proteins in the tested food item.

c) Fats: Fats are energy-giving food. They provide us with more energy when used up by the body.
  • Fats are stored in our body for future use.
  • Fats can be obtained both from animals and plants.
  • Fats from animal sources include milk, butter, ghee, cheese and meat.
  • Fats from plants are called as oils.
  • Seeds like mustard, sesame, groundnut, soyabean, coconut, sunflower, safflower can be used to produce oils.

Test to confirm the presence of fat
The following steps are performed to test the presence of fat in a food item.
  • Take a small quantity of the food item to be tested.
  • Wrap the food item in a small piece of paper.
  • Crush the food item wrapped in the paper.
  • Straighten the paper.
  • Dry the paper by keeping it in sunlight for a while.
  • Observe the paper.
  • An oily patch on the paper indicates the presence of fat in the tested food item.

d) Vitamins and minerals: These are the materials which occur both in plants and animals.
  • Vitamins protect our body from diseases.
  • Vitamins are required in small amounts but they are necessary in our diet. Deficiency in vitamins causes many diseases.
  • Vitamins are present in two categories, fat soluble vitamins and water soluble vitamins.
  • A person can maintain his health by maintaining balance of vitamins and minerals in the food.
  • Vitamins and minerals are present in more quantities in fruits and vegetables.

e) Dietary fibres: In addition to all these substances, dietary fibres are important materials in our food.
  • Dietary fibres do not release energy. These are also termed to be roughage. 
  • They help us in easy digestion of food.
  • They provide us bulkness in the stomach. We feel stomach full of food.
  • Green vegetables and leafy vegetables are rich in fibre content.
  • Beans, pulses whole grains, unpolished rice are also good sources of dietary fibres.

f) Water: Water is an essential substance in our food. It helps in easy passage of food.
  • 70% of our body is made up of water.It dissolves many substances in itself. 
  • Water is an essential substance in our food. 
  • It protects us from dehydration.
  • It helps in easy passage of food. It dissolves many substances in it.
  • Water also provides us some minerals.
  • Water forms the liquid medium of blood. It acts as main transport channel throughout the body.

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Activities & Simulations

Activity 1
Stanford.edu has created an interesting and interactive animation to cover almost all the topics related to nutrition. This  includes explanation about the importance of food, digestive system, nutrients of our diet and mainly balanced diet. It has aslo added a note on the types of nutrients in our food and their uses. Interactive quiz creates interest in students.
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Activity 2

Intel.co.uk has created a  template which seems to be a virtual lab.This activity helps the student in gaining the information about tests which are performed on different food stuffs. This information is necessary to know about the nutrient present in the food sample given in larger amounts. It gives the student a clear-cut idea aout the experiment, materials required and mainly the procedure in which experiment has to be performed.  
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