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Detection of Adulterants in Food Stuffs

 

Investigatory project on brief study of the detection of presence of adulterants in food-stuffs

Introduction


Often many of the food—stuffs bought from the market are adulterated. This causes serious diseases like cancer, asthma, ulcers, etc. Chilli powder is sometimes adulterated with brick powder, pepper is mixed with dried papaya seeds etc.


Aim


The aim of this project is to detect the presence of common adulterants in food—stuffs such as red chilli powder, pepper, turmeric, butter, sugar etc.


Requirements


1. Samples of Chilli powder, turmeric-powder, sugar etc.

2. Dil. HNO3

3. KI solution


Procedure


a) Detection of red lead in chilli powder


Add dil. HNO3 to a sample of chilli powder, shake and filter. Add KI solution to the filtrate. Yellow precipitate indicates the presence of lead salts in chilli powder. Nitric acid converts lead salt to lead nitrate which forms yellow lead iodide with potassium iodide.


Pb(NO3)2 + 2KI —> PbI2 + 2KNO3


b) Detection of yellow lead salts in turmeric powder


Add conc. HCl to a little of the given turmeric powder. Formation of a magenta colour shows the presence of yellow oxides of lead in the turmeric powder.


c) Detection of dried papaya seeds in pepper


Add a small amount of the pepper to be tested to a beaker containing water and stir. Being lighter, dried papaya floats on water while pure pepper settles to the bottom.


d) Detection of brick powder in chilli powder


Add some of the given chilli powder to water taken in a beaker. Chilli powder floats on water and brick powder settles down.


e) Detection of chalk powder and washing soda in sugar


Add diI. HCl to a little of the sugar. Brisk effervescence of CO2 shows the presence of chalk powder or washing soda in it. Carbonates react with dil. HCl to liberate carbon dioxide as brisk effervescence


Na2CO3 + 2HCl —> 2NaCI + CO2 + H2O


f) Detection of insoluble impurities in sugar


Add water to the sugar sample and stir. Pure sugar dissolves while insoluble impurities settle to the bottom.


VIVA QUESTIONS WITH ANSWERS


1. What is the common adulterant in chilli powder?


Ans: Brick powder or red lead


2. What is the adulterant in pepper?


Ans: Dry papaya seeds


3. How will you detect red lead in chilli powder?


Ans: Chilli powder is heated with dil. HNO3. To this solution potassium iodide solution is added. A yellow precipitate shows the presence of red lead.


4. What is the yellow precipitate formed?


Ans: It is lead iodide


5. How will you detect papaya seeds in pepper?


Ans: Add the sample to water taken in a beaker. If papaya seeds are present they will float on the surface of water and pepper will settle down.


6. How will you detect chalk powder in sugar?


Ans: Add dil. HCl to the sample. A brisk effervescence shows the presence of chalk powder.


7. What is the gas that evolves during the addition of dil. HCl?


Ans: Carbon dioxide

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