Food Tests

Question 1

How do you carry out a food test practical?

Answer 1

1. Take the food sample and grind it using a mortar and pestle, then mix with distilled water to make a paste.
2. Transfer paste to a beaker and then add more distilled water. Then stir so the chemicals in the food dissolve in the water.
3. Filter the solution to remove suspended food particles.

Question 2

How do you test for reducing sugars E.g. glucose?

Answer 2

1. Place 2cm³ of food solution into a test tube.
2. Add 10 drops of benedict’s solution. (blue in colour)
3. Place test tube in a beaker that is half full with hot water.
4. Leave for around 5 mins.
5. If sugars are present, the solution will change colour dependant on how much sugars are present.
   Lot of sugar- brick red, not much sugars- green

Question 3

How do you test for starch?

Answer 3

1. Place 2cm³ of food solution into a test tube.
2. Add a few drops of iodine solution into the test tube. (orange in colour)
3. If starch is present, the iodine solution will turn blue/ black.
4. Solution will stay orange if no starch present.

Question 4

How do you test for protein?

Answer 4

1. Place 2cm³ of food solution into a test tube.
2. Then add 2cm³ of biuret solution. (blue in colour)
3. If proteins are present then the solution will change to purple/ lilac.

Question 5

How do you test for lipids?

Answer 5

• Do Not filter lipid solution before testing because molecules will stick to filter paper

1. Place 2cm³ of food solution into a test tube.
2. Add a few drops of distilled water and a few drops of ethanol.
3. Gently shake the solution.
4. If lipids are present then a while, cloudy emulsion forms.