2C Food Tests

Question 1

How do you carry out qualitative test to detect the presence of sugars

Answer 1

Benedict’s test
Transfer 5cm3 food sample to a test tube
Set water bath to 75’
Add some Benedict
leave test tube in water bath for five minutes
The solution will change from a normal blue colour to green yellow Or red depending on the amount of sugar in the food

Question 2

How do you prepare food sample

Answer 2

Get a piece of your food and break it up using a pestle and mortar
Transfer the ground out food to beaker and add some distilled water
Give the mixture a stir with a glass rod to dissolve some food
Filter the solution is in a funnel lined with filterpaper

Question 3

How do you carry out qualitative test to detect the presence of starch

Answer 3

Iodine test
Put 5CM3 of food sample in a test tube
Add a few drops of ID solation and gently shake the tube if this sample contain starch the colour of the solution will change from brownie orange to black

Question 4

How do you carry out qualitative test to detect the presence of proteins

Answer 4

Biuret test
Transfer 2CM3 of food sample to test tube
Add 2CM3 of biuret solution to the sample and mix by gently shaking
If the sample contains protein the solution will change from blue to pink or purple

Question 5

How do you carry out qualitative test to detect the presence of lipids

Answer 5

Sudan III test
Prepare food sample without filtering it and transfer 5CM to a test tube
Add fridge drops of Sudan III stain solution to the test tube and gently shake
The solution stains lipids if the sample contains lipid the mixture will separate to 2 layers the top layer will be bright red