Required Practical 4: Food Tests

Question 1

4 Steps to prepare a solution

Answer 1

Grind the food sample with distilled water using a mortar and pestle.

Transfer the paste into a beaker and add more distilled water. Stir so the chemicals in the food dissolve.

Filter the solution to remove extra food particles.

3cm cubed of the solution into a test tube.

Question 2

How do you test for starch?

Answer 2

Add a few drops of iodine which is Orange

If there is Starch then it will go Blue-Black

Question 3

How do you test for reducing sugars?

Answer 3

Add 10 drops of Benedict’s Solution which is Blue

Add the test tube to a hot water bath at around 80 degrees

Leave this for 5 mins

If there is Sugar then it will go Green if there is little sugar, Yellow is in between or Red if there are loads

Safety: When the test tube is in the water bath make sure that the tube is pointed away from you

Question 4

How do you test for proteins?

Answer 4

Add an equal amount of Biuret Solution which is Blue

If there is Protein then it will go Purple-Pink

Question 5

How do you test for lipids(fats)?

Answer 5

Add an equal amount of Sudan III Solution

Gently shake the test tube to mix

If there are Lipids then a red-stained oil layer will separate and float on the surface

Safety: Sudan III contains ethanol so is highly flammable