CBSE Biology Experiment Food Sample Test for Starch and Adulteration

Starch is a complex carbohydrate which is a polymer of glucose molecules joined by 1,4 carbon linkages. Starch containing foods are important in a balanced diet as they provide energy and help in growth and development of an organism. Adulterants are harmful ingredients added to the daily food which appears and taste like the original food but do not have the same nutrient value. Excessive consumption of such adulterants can cause cancer, stomach ulcers, brain damage, etc.

Table of Contents

• Aims 

• Requirements 

• Theory 

• Methodology 

• Observations 

• Conclusion 

Aims 

(1) To determine starch content in the food sample.  

Requirements

Cooked rice, potato, and bread, test tubes, Iodine solution, distilled water, dropper.

Theory

Starch is made up of carbon, hydrogen, and oxygen. Many moieties of glucose join together and form starch. Iodine solution is used to detect the presence of starch. Iodine converts starch containing food samples blue-black in colour.

Procedure

1. Add little cooked rice and water into the test tube.

2. Add 2-3 drops of iodine solution in the test tube and shake well.

3. Observe the change in colour of the sample.

4. Follow the same procedure for other food samples such as potato and bread and see the colour change.

Observations

After the addition of iodine solution to the various food samples, there was a formation of blue-black colouration.

Starch detection

Result

Iodine solution when comes in contact with starch, a blue-black colour develops and hence we can conclude that the following food samples cooked rice, potato, and bread contains starch.

(2) To perform food sample tests for determining adulteration.

Requirements

Test tubes, distilled water, dropper, dal, Milk, ghee, furfural solution, conc. HCl solution, iodine solution.

Theory

A) Metanil yellow is a dye which is banned to be used as a food colour. It gives the classic yellow colour to dal and turmeric. It has harmful effects on the liver, intestine, and brain.

B) In milk, starch is used as an adulterant as it increases the solid content of the milk but reduces the fat content. As a result, adulterated milk appears thicker and heavier, same as non-adulterated milk. Pure milk when mixed with iodine solution shows coffee shade colour while adulterated milk gives a blue-black colour.

C) Vanaspati ghee is a substitute of pure cow ghee and is made from palm oil. Vanaspati ghee is partially hydrogenated vegetable oil which is cheaper and easily available as a replacement to pure ghee and hence is used as an adulterant.

Food Adulteration Experiments

Precautions

1. All reagents or chemicals are harmful, keep it away from eyes, nose, skin etc.

2. Clean the test tube before and after use.

Lab Manual Questions

1. What is the stored food in plants?

Ans: The food material in plants is starch.

2. Potatoes taste sweet after a few days. Explain.

Ans: Potatoes contain starch which is made of many sugar moieties, hence as potatoes    age over time, this starch is broken down into sugars and hence tastes sweet.

3. List common adulterants used in food.

Ans: Common adulterants used are:

• Brick powder in red chilli powder

• Urea in sugar

• Mustard seeds in argemone seeds

• Khesari dal in Arhar dal

4. What is the adulteration of food?

Ans: The mixing of cheaper food items with regular food which degrades the nutrients present in the food is known as adulteration of food. Adulteration is majorly done to make the product appear attractive, to make the product cheap, and to meet the daily food requirement of a rapidly increasing population. 

Viva Questions

1. Name the subunits of starch.

Ans: Starch is made of glucose subunits.

2. Which is the common source of starch?

Ans: Plants are a common source of starch. 

3. Reserve food material in animals?

Ans: In animals’ glycogen is the reserved food in animals.

4. Name adulterant present in milk.

Ans: A common adulterant of milk is starch which makes milk appear thick and fat.

5. Name the adulterant present in turmeric.

Ans: Adulterant present in turmeric is metanil yellow.

6. Name a chemical which assists in the detection of starch.

Ans: Iodine solution, a Brownish-yellow colour which turns blue-black comes in contact with starch.

7. Name an important chemical required to detect vanaspati adulterant.

Ans: Chemicals required to detect vanaspati in ghee is Conc. HCl and Furfural solution.

8. What does FSSAI stand for?

Ans: FSSAI stands for Food safety and Standards authority of India. It keeps a check on the quality of food supplied.

9. What do FPO and Agmrk stand for?

Ans: FPO - Food Products order

Agmark - Agriculture Marketing

10. What are adulterants of coffee? 

Ans: Adulterants of coffee are powdered date seeds and tamarind powder.

Practical Based Questions

1. Name the complex carbohydrates found in plants.

1. Glucose

2. Fructose

3. Maltose

4. Starch

Ans: Starch 

2. Which of the following is an example of simple sugar?

1. Starch

2. Cellulose

3. Table sugar

4. Glucose

Ans: Glucose

3. Which material is added that helps gain more profit and deteriorates the quality of the food item?

1. Drugs

2. Yellow dal

3. Milk

4. Adulterant

Ans: Adulterant

4. Shyam wanted to check the starch content of roti. Which chemical is used to test starch?

1. Iodine

2. Safranin

3. Methylene blue

4. Crystal violet

Ans: Iodine

5. Which solution is used to detect the presence of vanaspati in ghee?

1. Furfural solution 

2. Iodine

3. Crystal violet

4. Formic acid

Ans: Furfural solution 

6. Iodine test shows the presence of:

1. Carbohydrates

2. Sugars

3. Starch

4. Proteins

Ans: Starch

7. Which acid is used to detect adulterants in dal?

1. Sulphuric acid

2. Conc. Hydrochloric acid

3. Conc. Nitric Acid

4. Ammonia solution

Ans: Conc. Hydrochloric acid

8. Commonly used adulterant in chilli powder is?

1. Red colour

2. Pink colour

3. Dust 

4. Brick powder

Ans: Brick powder

9. Which one will show a positive starch test?

1. Tamarind

2.  Soyabean

3.  Potato

4.  Pineapple

Ans: Potato

10. Which reagent is used to detect adulteration in ghee and gives pink colour? 

1. NaOH

2. H20

3. Furfural solution and HCl

4. HCl

Ans: Furfural solution and HCl

Summary

Starch is an important component of our daily diet and is a rich source for providing energy to the body. When digested starch is broken down to glucose which provides direct energy to the body. To detect the presence of the starch in a food item, a starch test is performed. Adulterants are added to the food items to contaminate them and reduce nutrient quality of the food item. It is done to gain some extra profit. Common adulterants used are starch, vanaspati, sugar syrup, papaya seeds, metanil dal, etc.