Required practical food tests

Question 1

What are the different reagents?

Answer 1

carbohydrates, lipids and proteins

Question 2

What is the test for sugars?

Answer 2

Benedict’s test:

1) Add Benedictus solution to food
2) Heat in water bath
3) Negative blue, positive: green, yellow, or red brick depending on concentration

Hazards:
Wear safety goggles.
Benedict’s solution is an irritant.
Avoid contact with skin and eyes.

Question 3

What is the test for starch?

Answer 3

Iodine test:

1) Add 5cm of food sample to test tube
2) Add a few drops of iodine solution
3) Give a gentle shake

Results:
Positive - blue/black
Negative - orange/brown

Question 4

What is the test for proteins?

Answer 4

Biuret test:

1) Add 1cm of sample to a test tube
2) Add 1cm of buret solution to sample
3) Gentle shake

Results:
Positive - purple
Negative - Blue

Hazards:
Wear safety goggles.
Biuret solution A is corrosive.
Biuret solution B is an irritant.
Avoid contact with skin and eyes.

Question 5

What is the test for fats (lipids)?

Answer 5

Sudan 3 test:

1) Add equal amounts of food and sample
2) Add drops of Sudan and shake gently

Results:
Positive - red layer on surface

Hazards:
Wear safety goggles.
Sudan III solution is flammable as it is dissolved in alcohol.
Avoid contact with skin and eyes.